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Paleoenvironmental and paleoecological trends leading up to the end-Triassic mass extinction event
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Paleoenvironmental and paleoecological trends leading up to the end-Triassic mass extinction event
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Content
PALEOENVIRONMENTAL AND PALEOECOLOGICAL TRENDS
LEADING UP TO THE END-TRIASSIC MASS EXTINCTION EVENT
by
Ekaterina Larina
____________________________
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(GEOLOGICAL SCIENCES)
August 2021
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ACKNOWLEDGEMENTS
This project has been made possible through the support and collaborations of many faculty
members, fellow students and the staff in the Department of the Earth Sciences at the University
of Southern California and colleagues from various universities around the globe. The first and
most instrumental person in furthering my research and career is my advisor Dave Bottjer who
devoted countless hours to reviewing my work and advising me. Dave’s unwavering support and
encouragement made this project possible and helped me to grow as a geologist and an individual.
Special thanks is given to Frank Corsetti for the help and support with developing ideas for my
project, constructive criticism and extending my skillsets in petrography, just to name a few.
Extended gratitude to the dissertation committee Dave Caron, Will Berelson and Austin Hendy for
advising me during my studies.
I would like to thank my collaborators John-Paul Zonneveld, Aaron Celestian, Jake Bailey,
Sylvain Richoz, Emilia Jarochowska, Niklas Hohmann, Garett Brown, Will Berelson, Josh West,
Joyce Yager and Alyson Thibodeau who played a pivotal role in the development and
implementation of various projects throughout my studies. Special thanks to JP Zonneveld and
Sylvain Richoz for showing me the Triassic/Jurassic sites, constructive discussions, and assistance
on the field. I would like to thank Nikolas Thibault for providing a copy of the figure of the Eiberg
section. Special thank you to Dave Taylor and Jean Guex for helping me with macrofossil
identification and to Luka Gale for helping me with foraminifera identification. I am grateful to
Nick Rollins, Peter Wynn, Dylan Wilmeth and Thomas Orvis for assistance in the laboratory.
I would like to thank Niraj Vora, Camilo Cavidad, Dan Farella, Lauren Hansen, Valentine
Payers, Abraham Polakunnil, Isaiah Smith, Emilia Jarochowska, and Niklas Hohmann for
tirelessness assistance on the field and discussions related and unrelated to the project. I would like
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to thank my cohort Amanda Godbold, Yubin Raut, Alison, Cribb, Jeff Thompson, Liz Petsios,
Lydia Tackett, Claire Johnson, Becky Wu, Nathan Caroll, Hank Wooley, Kiersten Formoso,
Jayme Feyhl-Buska, Jessica Zaiss, Emily Burt, Diana Bojanova, Tarryn Cawood, Jessica
Stellmann, Kenny Bolster, Olivia Piazza, Hyejung Lee, Alex Hatem, Abby Lunstrum, Rachel
Kelly for your moral support and for making these last six years filled with exciting science, fun
times and positive attitude. I apologize in advance for inevitably leaving someone’s name off.
I am forever grateful to my friends and family whose trust and support helped me to
persevere with my thesis project and made the last six years an unforgettable experience. Special
thanks to my partner Niraj Vora who was extremely patient and supportive during my countless
hours of work and numerous weeks of absence due to field work and other career-related activities.
This work has been possible due to funding from the NSF Earth-Life Transitions (ELT)
program (EAR-1338329), NSF GRFP No. 2013171808, USC Research Enhancement Fellowship,
Student Research Grant (SEPM), Student Grant (GSA), Lerner Gray Scholarship (AMNH), and
Department Student Grant (USC).
This dissertation is dedicated to my mom, Svetlana Larina, in gratitude for her infinite
trust, support and encouragement with my various endeavors. I would not be where I am if it was
not for my mom.
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Table of Contents
Acknowledgements ......................................................................................................................... ii
List of Tables ................................................................................................................................. vii
List of Figures ............................................................................................................................... viii
Abstract ........................................................................................................................................... xi
Chapter 1: Introduction to the end-Triassic mass extinction ........................................................... 1
1.1.The end-Triassic mass extinction as an analogue to the current climate change .................. 1
1.2.Biotic turnovers during the end-Triassic mass extinction ..................................................... 2
1.3.Central Atlantic Magmatic Province and the end-Triassic mass extinction .......................... 4
1.4.Chemostratigraphic record of the end-Triassic mass extinction ........................................... 5
Carbon Isotopes ....................................................................................................................... 5
Mercury Record ....................................................................................................................... 6
1.5. Drivers of the end-Triassic mass extinction ......................................................................... 7
Marine Anoxia ......................................................................................................................... 7
Warming .................................................................................................................................. 8
Ocean acidification ................................................................................................................. 9
1.6. Dissertation purpose and significance ................................................................................ 10
References ..................................................................................................................................... 15
Figures ........................................................................................................................................... 29
Chapter 2: Ecosystem change and carbon cycle perturbation began before the end-Triassic mass
extinction ...................................................................................................................................... 32
Abstract .......................................................................................................................................... 32
2.1 Introduction ......................................................................................................................... 33
2.2. Background ............................................................................................................................. 33
2.2.1. End-Triassic mass extinction and carbon cycle disruption ........................................ 33
2.2.2. Geological, paleoenvironmental and paleoecological setting ................................... 36
2.3 Materials and Methods ............................................................................................................ 38
2.3.1. Carbon isotope, carbonate and organic carbon measurements ................................ 38
2.3.2. Petrographic analysis ................................................................................................. 39
2.3.3. Mercury measurements .............................................................................................. 40
2.3.4. Paleoecological analysis ............................................................................................ 40
2.4 Results ..................................................................................................................................... 41
2.4.1. Carbon isotopes and organic carbon ......................................................................... 41
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2.4.2. Petrographic investigation ......................................................................................... 43
2.4.3. Hg concentrations ...................................................................................................... 44
2.4.4. Paleoecology ............................................................................................................... 45
2.5. Discussion and Conclusions .................................................................................................. 46
References ..................................................................................................................................... 52
Figures ........................................................................................................................................... 61
2S Supplementary Information for Chapter 2 .............................................................................. 69
Chapter 3: Uppermost Triassic phosphorites from Williston Lake, Canada: link to episodic
euxinia in Northeastern Panthalassa ............................................................................................. 73
Abstract .......................................................................................................................................... 73
3.1. Introduction ........................................................................................................................ 74
3.2.Study area ............................................................................................................................ 76
3.3. Results ................................................................................................................................ 77
3.3.1. Description of phosphorite deposits ......................................................................... 77
3.3.2. Microbial mineralization .......................................................................................... 78
3.4. Discussion ........................................................................................................................... 80
3.5. Conclusions ........................................................................................................................ 84
3.6. Methods .............................................................................................................................. 85
References ..................................................................................................................................... 86
Figures ........................................................................................................................................... 91
Chapter 4: Microfacies and macrofaunal analysis of upper Rhaetian Eiberg Member sequences
from the Northern Calcareous Alps .............................................................................................. 99
Abstract .......................................................................................................................................... 99
4.1. Introduction ...................................................................................................................... 100
4.2. Geological Setting ............................................................................................................ 101
4.3. Materials and Methods ..................................................................................................... 105
4.3.1. Macrofaunal analysis ............................................................................................. 105
4.3.2. Microfacies analysis ............................................................................................... 106
4.3.3. Data Analysis .......................................................................................................... 106
4.4. Description of localities .................................................................................................... 109
4.4.1. Kuhjoch, GSSP locality (47º29’02”N, 11º31’50”E) .............................................. 109
4.4.2. Schlossgraben (47º28’32”N, 11º28’54”E) ............................................................. 112
4.4.3. Juifen (47º32’53”N, 11º37’32”E) .......................................................................... 113
4.4.4. Eiberg (47°33’00”N, 12°10’07”E) ......................................................................... 114
4.4.5. Restentalgraben (47°50’27”N, 14°32’21”E) .......................................................... 117
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4.5. Results .............................................................................................................................. 119
4.5.1. Microfacies analysis ............................................................................................... 119
4.5.2. Faunal data ............................................................................................................. 122
4.5.3. Species turnover ..................................................................................................... 126
4.5.4. Two-way cluster analysis ....................................................................................... 127
4.5.5. Ordination analysis ................................................................................................ 128
4.6. Discussion ......................................................................................................................... 129
4.6.1. Facies interpretation .............................................................................................. 129
4.6.2. Evolution of facies and environments through time ............................................... 131
4.6.3. Faunal distribution ................................................................................................. 134
4.6.4. Implications for the end-Triassic mass extinction in the Northern Calcareous Alps
................................................................................................................................. 137
4.7.Conclusions ....................................................................................................................... 140
References ................................................................................................................................... 141
Figures and tables ........................................................................................................................ 154
Chapter 5: Global biotic and geochemical trends leading up to the end-Triassic mass extinction
..................................................................................................................................................... 195
Abstract ........................................................................................................................................ 195
5.1. Introduction .......................................................................................................................... 196
5.2. Biotic turnovers or benthic paleoecology ............................................................................. 198
5.3. Paleoenvironmental trends during the Late Triassic ............................................................ 201
5.4. Discussion ............................................................................................................................. 205
5.5. Conclusions .......................................................................................................................... 207
References ................................................................................................................................... 209
Figures ........................................................................................................................................ 219
Chapter 6: Conclusions ............................................................................................................... 227
References ................................................................................................................................... 230
APPENDIX A. Figures and tables for Chapter 2 ........................................................................ 232
APPENDIX B. Dataset for Chapter 3 ......................................................................................... 241
APPENDIX C. Figures and tables for Chapter 4 ........................................................................ 259
APPENDIX D. Tables for Chapter 5 .......................................................................................... 305
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LIST OF TABLES
Chapter 4 Tables.
Table 1. Lithofacies types of the Eiberg and lower Tiefengraben Member and their depositional
environment. ................................................................................................................................ 176
Table 2. Results of turnover analysis for Eiberg and Restentalgraben sections .......................... 190
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LIST OF FIGURES
Chapter 1 Figures.
Figure 1. Generic diversity among major marine animal groups through the Phanerozoic .......... 29
Figure 2. Summary of major geochemical, biotic and environmental perturbation events across
the Triassic/Jurassic (=T/J) boundary. ........................................................................................... 30
Figure 3. Late Triassic paleogeographic map showing studied localities and original extent of the
Central Atlantic Magmatic Province (CAMP) .............................................................................. 31
Chapter 2 Figures.
Figure 1. Lower Jurassic paleogeographic map showing sites with the documented precursor
carbon isotope excursion (precursor CIE) ..................................................................................... 61
Figure 2. Composite stratigraphic section from Ferguson Hill, Muller Canyon, Nevada from
Thibodeau et al. (2016) and this study. ......................................................................................... 62
Figure 3. Stratigraphic section of the studied site showing macrofaunal, geochemical and
petrographic data ........................................................................................................................... 63
Figure 4. ......................................................................................................................................... 64
Figure 5. ......................................................................................................................................... 66
Figure 6. ......................................................................................................................................... 68
Chapter 3 Figures.
Figure 1. Paleogeography and modern location of study localities. .............................................. 91
Figure 2. Stratigraphic columns of studied sections showing depositional environment ............. 92
Figure 3. Photomicrographs of phosphatic coated grains ............................................................. 93
Figure 4. Photomicrographs and SEM images of putative microbial structures, euendolith borings,
and pyrite framboids. ..................................................................................................................... 95
Figure 5. Raman spectroscopic analysis ........................................................................................ 97
Chapter 4 Figures.
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239
Figure 1. ....................................................................................................................................... 154
Figure 2. Stratigraphy of the Eiberg Basin of the Northern Calcareous Alps. Arrows illustrate
onlap of Kendlbach Formation on top-Rhaetian unconformity during transgressive cycle. ....... 155
Figure 3. Chrono- and bio- stratigraphy of the Rhaetian Stage ................................................... 156
Figure 4. Representative examples of T-bed with bituminous layer. .......................................... 157
Figure 5. Extinction interval spanning T-bed followed by the Grenzmergel Bed and Schattwald
Beds ............................................................................................................................................. 158
Figure 6. Map showing the locations of studied localities .......................................................... 159
Figure 7.Kuhjoch locality ............................................................................................................ 160
Figure 8. Kuhjoch locality. .......................................................................................................... 161
Figure 9. Schlossgraben locality. ................................................................................................. 162
Figure 10. Field photos of Schlossgraben locality. ..................................................................... 163
Figure 11. Juifen section .............................................................................................................. 164
Figure 12. Juifen locality ............................................................................................................. 165
Figure 13. Eiberg locality ............................................................................................................ 167
Figure 14. Field photos of Eiberg section ................................................................................... 168
Figure 15. Photos of macrofauna found at the Eiberg section.. .................................................. 170
Figure 16. Restentalgraben locality. ............................................................................................ 171
Figure 17. Field photos of Restentalgraben locality. ................................................................... 172
Figure 18. Photos of macrofauna found at the Restentalgraben section ..................................... 174
Figure 19. Photomicrographs of Microfacies 1 – mudstone ....................................................... 177
Figure 20. Photomicrographs of Microfacies 2 – silty mudstone/marl ....................................... 179
Figure 21. Photomicrographs of Microfacies 3 – bioclastic wacke- to packstone ...................... 181
Figure 22. Photomicrographs of Microfacies 4 – bioclastic pack- to rudstone... ........................ 183
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239
Figure 23. Photomicrographs of Microfacies 5 – coated bioclastic grainstone. .......................... 185
Figure 24. Stratigraphic log of the Juifen section. ....................................................................... 187
Figure 25. Stratigraphic log of the Eiberg section ...................................................................... 188
Figure 26. Stratigraphic log of the Restentalgraben section ....................................................... 189
Figure 27. Sequence stratigraphic interpretation of the Eiberg section ....................................... 191
Figure 28. Sequence stratigraphic interpretation of the Restentalgraben section with corresponding
turnover results ........................................................................................................................... 192
Figure 29. Two-way cluster analysis of macrofaunal assemblage .............................................. 193
Figure 30. Nonmetric Multidimensional Scaling (=NMDS) showing samples as points. .......... 194
Chapter 5 Figures.
Figure 1. Schematic diagram of faunal and carbon perturbation events occurred during Late
Triassic along with a simplified organic carbon isotope curve. .................................................. 219
Figure 2. Reconstruction of Late Triassic globe showing the occurrence and distribution of
Animalia. The diagram is derived from the Paleobiology Database ........................................... 219
Figure 3. Paleoreconstruction of the Late Triassic globe showing fossil occurrences used in this
study across Boreal, Panthalassic, and Tethys basins. ................................................................ 221
Figure 4. Marine inverterbrates diversity across basins (A) and across taxa (B) during Late Triassic
to Lower Jurassic ......................................................................................................................... 222
Figure 5. Generic richness of marine invertebrates (Brachiopoda, Bivalvia, Cephalopoda, and
Gastropoda) from Carnian to Sinemurian Stage ......................................................................... 223
Figure 6. Marine invertebrate generic occurrences across basins (A) and across taxa (B) during
Late Triassic to Lower Jurassic. .................................................................................................. 224
Figure 7. Generic occurrences of marine invertebrates (Brachiopoda, Bivalvia, Cephalopoda, and
Gastropoda) from Carnian to Sinemurian Stage ......................................................................... 225
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ABSTRACT
The end-Triassic mass extinction (ETE) is one of the biggest biotic crises that has occurred
during geological history and the main cause is generally attributed to the emplacement of the
Central Atlantic Magmatic Province (CAMP) ~201.51 million years ago. The ETE was the most
devastating extinction for the so-called Modern Fauna
and the triggering mechanisms associated
with the ETE, such as global warming, ocean acidification, ocean anoxia and sea-level changes,
are analogous to imminent environmental perturbations. The amount of CO2 injected into the
atmosphere during each CAMP magmatic pulse rivals anthropogenic CO2 emission projected for
the 21
st
century. Although the ETE and its aftermath are well documented, the conditions leading
up to the ETE remain poorly understood. Yet, most recent studies emphasize the complexity of
the pre-extinction scenario and the importance of deciphering precursor events to the ETE if the
mechanisms for this "Big 5" mass extinction are to be fully delineated. Elucidating the triggering
mechanisms of past extinction events and their effects on Earth system behavior are particularly
critical nowadays as we are entering the sixth mass extinction.
This study aims to resolve environmental conditions in marine realm that acted in the lead-
up to the ETE and its impact on the complexity of marine benthic ecosystems. Specifically, the
precursor events during the late Triassic have been explored at different scales varying from micro-
(microns to cms) to macro-scale (ms to kms) across different geographic areas. Two regional case
studies of three sections from British Columbia and one from Nevada, USA, are presented to
establish biogeochemical and biotic changes in Panthalassic realm. Biogeochemical and
sedimentological analyses integrated with quantitative analysis of marine benthic community from
the Panthalassic sections reveal episodic deoxygenated events and restructuring of marine benthic
community towards more low oxygen tolerant taxa and lower diversity preceding the main phase
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of CAMP volcanism. At Ferguson Hill, Nevada, these changes closely follow the “precursor”
negative carbon isotope excursion implying a truly global extent of the pre-extinction carbon cycle
perturbation and highlighting the detrimental effect of fluctuations in carbon cycle on shallow
marine ecosystems. In contrast, regional scale study of upper Rhaetian sections in Tethys realm
reveals an ecologically diverse and robust marine benthic community across different depositional
environments all the way up to the main phase of CAMP volcanism implying the sudden tempo
of ecological changes in Tethys compared to the more protracted nature of ecological shifts
recorded in the Panthalassa. Despite disparities in paleoenvironmental and paleoecological trends
in the lead up to the ETE across the basins, the severity of the extinction is apparent across the
globe once the main phase of CAMP volcanic activity was initiated.
Using the Paleobiology Database and published literature, this study evaluated the
extinction pattern of marine invertebrates on a stage-by-stage basis across different carbon cycle
perturbation events during the Late Triassic. The quantitative analysis of marine invertebrates
shows reduced generic richness in marine invertebrates across the bains implying an important
role of the biotic turnover and carbon cycle perturbation event that happened at the
Norian/Rhaetian boundary, however the biotic pattern is complicated by low origination rate and
short duration of the Rhaetian stage. This work highlights the importance of pre-extinction studies
at different temporal and spatial scales using integrative analysis of geochemical, sedimentological
and faunal datasets.
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CHAPTER 1. INTRODUCTION TO THE END-TRIASSIC MASS
EXTINCTION
1.1. The end-Triassic mass extinction as an analogue for current climate change
Mass extinctions have had a profound effect on the history of life via species extinction
and altering the structure of pre-existing ecosystems. Indeed, human civilization might be in the
midst of the sixth mass extinction based on the rate and mode of species extinction (e.g, Barnosky
et al., 2011; Wake and Vredenburg, 2008; Finnegan et al., 2015) predominantly as a result of
anthropogenic CO2 input (e.g., IPCC 2014; Ceballos et al., 2015). Understanding the mechanisms
of past extinction events and related ecosystem responses, especially with respect to rising CO2
levels, is essential for future decisions in policy making targeted to prevent further environmental
and ecological crises that our world faces today.
The end-Triassic mass extinction (ETE) is generally associated with the eruption of the
Central Atlantic Magmatic Province (CAMP) ~201.5 million years ago (Blackburn et al., 2013;
Wotzlaw et al., 2014). During the ETE, approximately 80% of all marine and terrestrial species
became extinct making it the second biggest biodiversity and the third biggest ecological crisis
during the Phanerozoic (Sepkoski 1996; Stanley, 2007; Alroy et al., 2010; McGhee et al., 2004,
2013) (Fig. 1). The killing mechanism is mainly attributed to CO2 - induced environmental changes
as a result of CAMP eruptions (e.g, Schaller et al., 2012; Jaraula et al., 2013; Palfy and Kocsis,
2014, Thibodeau et al., 2016). Proposed causes of global environmental stress include global
warming (McElwain et al. 1999; Wignall 2001; Palfy and Kocsis, 2014), global cooling (Guex et
al., 2004), ocean acidification (Hautmann 2004; Kiessling et al., 2007; Greene et al., 2012a,
2012b), sea-level changes (Hallam, 1981), and ocean anoxia (Hallam & Wignall 2000; Jaraula et
al. 2013; Kasprak et al., 2015; Larina et al., 2019; Atkinson and Wignall, 2019). Triggering
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mechanisms (such as rapid rates of CO2 input into the atmosphere) and associated causes
(including warming, anoxia, sea-level rise and ocean acidification) of the ETE are analogous to
daunting issues facing the world today. Despite the high relevance of the ETE to the current climate
change scenario or to the putative sixth mass extinction, it has been understudied compared to
other mass extinction events (Twitchett, 2006; Dunhill et al., 2017). In addition, the knowledge
base of the conditions leading up to the ETE is currently lacking, as the main focus has remained
on the timing associated with an initial emplacement of CAMP. Recent studies reveal that the pre-
extinction scenario might be more complex than currently thought (Davies et al., 2017; Yager et
al., 2017; Larina et al., 2019). Elucidating the paleoenvironmental conditions and ecological
structure during the pre-extinction time could potentially reshape our understanding of the end-
Triassic mass extinction triggering mechanisms and their effect on ecosystems.
1.2. Biotic turnovers during the end-Triassic mass extinction
The ETE had the most devastating impact on the clades that inhabit todays' oceans (so-
called Modern Fauna (Sepkoski, 1981)) compared to other extinction events in the Phanerozoic
(Fig. 1, 2). The fossil record indicates that ammonites, radiolarians, phytoplankton, scleractinian
corals, ichthyosaurs and temnospondyl amphibians were on the brink of extinction, with the total
loss of conodont species (Fig. 2) (Guex et al., 2004; van de Schootbrugge et al., 2007; Mander et
al. 2008; Mander and Twitchett, 2008; Kiessling et al., 2007; Fischer et al., 2014; Wintrich et al.,
2017; Konietzko-Meier et al., 2018). Specifically, the extinction selectivity was elevated against
reef dwelling organisms, inshore taxa, taxa with the preference for carbonate substrates, and low-
latitude taxa (Kiessling et al., 2007). The terrestrial record documents a high diversity loss in
sporomorphs, plants, and early Mesozoic vertebrates (McElwain et al., 1999; Thorne et al., 2011;
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239
Bonis and Kurschner, 2012; Davies et al., 2017). Dunhill et al. (2017) investigated the effects of
the ETE on functional diversity and composition of marine ecosystems using the Paleobiology
Database. Despite the severe loss of species, all functional groups persisted through the ETE with
high selectivity against sessile suspension feeders and calcareous fauna in tropical latitudes
(Dunhill et al., 2017; Greene et al., 2012a; Kiessling et al., 2007). The ecological characterization
of Triassic-Jurassic (T/J) marine fauna described by Opazo Mella (2012) from sections in Chile
records two spikes demonstrating species richness decline through the Rhaetian. The study
illustrates the high compositional turnover of 95% of taxa that occurred within the short period of
time across the T/J boundary resulting in the weakening of the ecological functionality of the
invertebrate marine assemblage. In addition, ecological diversity decreased by ~40% during the
Jurassic in Chilean sections. McRoberts et al. (2012) recorded a flourishing community of
eurytopic opportunistic bivalves at a time of initial crises that persisted into the peak of extinction
in the Tethys realm in the Northern Calcareous Alps, Austria.
The restructuring of ecological systems in the aftermath of the ETE caused a delay of two
million years before returning to pre-extinction ecological conditions (Fig. 2). The study of
Ritterbush et al. (2014) elucidates the ecological state of the marine biosphere in the aftermath of
the ETE. As the ecosystem started slowly to recover above the T/J boundary, siliceous sponges
spread across a midshelf habitat, in a "sponge takeover", for the following two million years in
Eastern Panthalassa (Ritterbush et al., 2014, 2015, 2016; Corsetti et al., 2015). An interweaving of
geochemical and ecological consequences in the aftermath of the ETE set up an unusual stage for
Mesozoic marine life (Ritterbush et al., 2014).
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1.3. Central Atlantic Magmatic Province and the end-Triassic mass extinction
The end-Triassic mass extinction has been linked to extensive volcanic activity from the
early break-up of the supercontinent Pangea, which led to the formation of a large igneous province
(LIP), the so-called Central Atlantic Magmatic Province, and subsequently the Atlantic Ocean
(e.g., Blackburn et al., 2013; Schaller et al., 2012; Dal Corso et al., 2012; Thibodeau et al., 2016;
Marzoli et al., 2018; Lindstrom et al., 2020).
CAMP is known as the largest igneous province and covered over 10 million km
2
on the
supercontinent Pangea (Fig. 1). The volume of CAMP magmas including those intruded at various
levels of the crust is estimated to be about 3 million km
3
found today across Africa, Europe, North
and South America (Marzoli et al., 2018; Tegner et al., 2020) (Fig. 1). Using high-precision U-Pb
dating of CAMP extrusive and intrusive rocks, it has been assessed that CAMP emplacement
occurred in four main phases over an 800,000 year interval (Schoene et al., 2010; Blackburn et al.,
2013; Davies et al., 2017; Heimdal et al., 2018, 2020). The oldest age for CAMP magmatism is
201.635 ± 0.029 Ma for the Kakoulima mafic intrusion in Guinea (Davies et al., 2017; Heimdal et
al., 2020) (Fig. 2). The Kakoulima intrusion is closely followed by the Messejana dyke in Spain,
and the Tarabuco mafic sill in Bolivia constituting the "early" phase of CAMP emplacement
(Heimdal et al., 2020). The "main" phase is marked by the CAMP sills into the Amazonas and
Solimoes basins and the North Mountain Basalts yielding the earliest age of 201.525 ± 0.065 Ma
(Davies et al., 2017; Heimdal et al., 2020).
The age for the ETE in terrestrial settings is estimated to be 201.564 ± 0.015 Ma based on
the U-Pb zircon dating of basalts and orbitally tuned sedimentary strata (Blackburn et al., 2013).
The ETE in marine settings yields an age of 201.51 ± 0.15 Ma based on age calibrations derived
from ash beds in Peru and the last occurrence of the last Triassic ammonoid Choristoceras
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crickmayi (201.51 ± 0.15 Ma) (Wotzlaw, et al., 2014). The ETE record in terrestrial and marine
settings overall overlaps, yet the age in continental settings needs to be refined further in the future
due to raised concerns over pollen and spore turnover (Fowell and Olsen, 1993) and a possible
hiatus in the Orange Mountain basalt in the Newark basin (Marzoli et al., 2004; Whiteside et al.,
2007; Wotzlaw et al., 2014; Tanner and Lucas, 2015; Davies et al., 2017). Mass extinction and
carbon cycle disruptions are geologically synchronous with radioisotopic ages of CAMP
extrusives and intrusives implying a temporal and likely causal link of the ETE and CAMP
emplacement (Marzoli et al., 2018). Although, there is consensus in the scientific community on
the role of CAMP during the ETE, the triggering mechanisms behind carbon cycle disruptions, the
primary role of CAMP extrusives versus intrusives and its effect on ecosystems are vigorously
debated (Nomade et al., 2007; Paris et al., 2012; Dal Corso et al., 2014; Davies et al., 2017;
Heimdal et al., 2020; Ruhl et al., 2020, Lindstrom et al., 2020).
1.4. Chemostratigraphic record of the end-Triassic mass extinction.
Carbon Isotopes
CAMP volcanic activity released large amounts of carbon either through direct volcanic
emissions from CAMP basalts (e.g., Dal Corso et al., 2014; Pálfy and Kocsis, 2014; Thibodeau et
al., 2016) or indirectly through thermogenic methane derived from organic rich sediments as a
result of CAMP intrusive activity (Ruhl and Kürschner, 2011; Ruhl et al., 2020; Heimdal et al.,
2020). Other proposed mechanisms for the source of
13
C-depleted carbon include release of marine
clathrates as a result of warming climate (Beerling and Berner, 2002; Ruhl et al., 2011; Korte et
al., 2019). A recent study suggests that a single CAMP volcanic eruption had a potential to affect
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the end-Triassic climate via the emission of 5 x 10
16
mol CO2 which is nearly equivalent to the
total amount of projected anthropogenic emissions over the 21
st
century (Capriolo et al., 2020).
Multiple negative carbon isotope excursions (CIEs) are documented worldwide in
association with the ETE, called “main”, “initial”, and “precursor” (e.g., Hesselbo et al., 2002;
Bachan et al., 2012; Yager et al., 2017; Zaffani et al., 2018; Korte et al., 2019; Heimdal et al.,
2020; Ruhl et al., 2020, Lindstrom et al., 2021; Larina et al., 2021). The correlation of CIEs in
different sites around the globe is mainly based on bio-, magneto-, and chemo- stratigraphy, and
faunal and floral turnover events (Zaffani et al., 2018). The magnitude of CIE records varies from
1-8‰ depending on paleogeographic location hampering the correlation with the CAMP volcanic
activity and its implications for the ETE (e.g., Korte et al., 2009; Yager et al., 2017; Schobben et
al., 2019; Ruhl et al., 2009, 2020; Lindstom et al., 2012, 2020). A recent study based on modeling
attributed these differences to extreme aridity across the western Pangean landmass causing lower
delivery of organic carbon to the Panthalassic continental shelf compared to a humid climate across
the central Pangean landmass that resulted in an increased delivery of terrestrial organic matter to
the Tethys basin (Bonis et al., 2010; Ruhl et al., 2020). The constraints on the duration, magnitude
and placement of CIEs are essential for disentangling carbon cycle evolution and its correlation
with biotic turnovers during the ETE.
Mercury record
Mercury has been used as a fingerprint for large igneous provinces in the stratigraphic
record (Thibodeau et al., 2016; Davies et al., 2017; Thibodeau and Bergquist, 2017; Percival et al.,
2017; Charbonnier et al., 2020). With respect to the ETE, an elevated amount of Hg (volcanic
origin) persisted through the extinction and depauperate intervals indicating that biota didn't begin
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to fully recover until the CAMP eruptions ceased as documented at Ferguson Hill, Nevada
(Thibodeau et al., 2016). Percival et al. (2017) performed mercury analysis in six other
Triassic/Jurassic sections around the globe corroborating the results of the Thibodeau et al. (2016)
study and provided mercury evidence for the pulsed nature of CAMP volcanism. Lindstrom et al.
(2019) analyzed the mercury record of marine and terrestrial Triassic/Jurassic sections in southern
Scandinavia and northern Germany confirming the pulsed and intense nature of CAMP volcanic
activity. In addition, their study documented a correlation between mutagenesis in land plants and
elevated levels of mercury inferring the cause-and-effect relationship between emissions of
CAMP-related toxic volcanogenic substances and the end-Triassic biotic collapse (Lindstrom et
al., 2019).
1.5. Drivers of the end-Triassic mass extinction
The close temporal link between CAMP-derived greenhouse gases and extinction implies
a cause-and-effect relationship but the direct killing mechanisms and their preponderance has been
widely disputed (e.g., Wignall and Atkinson, 2020). The main proposed drivers of the extinction
include increased temperatures (McElwain et al. 1999; Wignall, 2001; Pálfy and Kocsis, 2014;
Paris et al., 2016; Capriolo et al., 2020), oceanic anoxia (e.g., Richoz et al., 2012; Kasprak et
al.,2015; Schoepfer et al., 2016; Larina et al., 2019, 2021; Fujisaki et al., 2018; 2020; Wignall and
Atkinson, 2020; He et al., 2020) and ocean acidification (e.g., Kiessling et al., 2007; McRoberts
et al., 2012; Greene et al., 2012a, 2012b; Bachan et al., 2014).
Marine anoxia. –– Deoxygenation of ocean waters during the ETE is predominantly linked
to increased temperatures that initiated weathering feedback and nutrient delivery of P causing
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eutrophication and changes in ocean circulation leading to expansion of oxygen minimum zones
(Kasprak et al., 2015; Schoepfer et al., 2016; Fujisaki et al., 2020). The development of fluctuating
euxinic and anoxic conditions in the mid-Panthalassic Ocean during the end-Triassic is evidenced
by the biomarker isorenieratane, a fossilized pigment from green sulfur bacteria which is
suggestive of photic zone euxinia (Jaraula et al., 2013; Kasprak et al., 2015). Yet, the deep
Panthalassic Ocean was oxic as verified by iron speciation analysis (Sato et al., 2012) and redox-
sensitive element concentrations (Fujisaki et al., 2016) from deep-sea cherts and shales at the
Katsuyama section in Japan. In the Tethys realm, episodic anoxic and photic zone euxinic
conditions were predominantly restricted to shallow seas mainly following the end-Triassic mass
extinction as evidenced by the widespread deposition of black shales, pyrite framboid size analysis,
redox sensitive metals, and increased concentrations of the biomarker isorenieratane (Hallam,
1995; Richoz et al., 2012; Breward et al., 2015; Blumenberg et al., 2016; Jost et al., 2017; Atkinson
and Wignall, 2019). Regionally, Upper Triassic sections in Austria document anoxic conditions
within the T-bed comprising laminated strata and pyrite nodules deposited during the onset of the
ETE (Bonis et al., 2010; Ruhl et al., 2011; Hellebrandt et al., 2013). A recent study using
biogeochemical modeling proposed that pre-extinction oceans contained low sulfate
concentrations thus setting the stage for the development of widespread anoxia during rapid
warming events as the result of enhanced methane generation and concomitant elevated bottom-
water oxygen consumption (He et al., 2020).
Warming. –– The large amounts of CO2-bearing bubbles, the pulsed eruption and the
efficient degassing of CO2 from CAMP basaltic magmas (Barry et al., 2014; Capriolo et al., 2020)
severely induced extreme greenhouse conditions (Paris et al., 2016) leading to rapid warming
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events during the end-Triassic. The evidence of rapid warming events during the ETE is
corroborated by stomatal index data from Greenland, Sweden and Northern Ireland and pedogenic
carbonates from the Newark and Hartford basins (McElwain et al., 1999; Steinthorsdottir et al.,
2011; Schaller et al., 2011, 2012). The analysis of pedogenic carbonates from within the CAMP
documents a major increase in pCO2 after each major eruptive episode with a subsequent gradual
decline in atmospheric carbon dioxide levels due to chemical weathering of CAMP basalts
(Schaller et al., 2011, 2012).
Ocean acidification. – Ocean acidification invoked by the release of CO2 and volatiles from
CAMP intrusives and extrusives has been proposed as a key mechanism for the end-Triassic mass
extinction (e.g., Hautmann, 2004; Veron, 2008; Bernasconi et al., 2009; Clemence et al., 2010;
Kiessling and Simpson, 2011; Greene et al. 2012a, 2012b). Early diagenetic carbonates in the form
of unusual aragonite fan formations were documented at several Triassic-Jurassic sections and
were suggested as a response to ocean acidification underlying the ETE (Greene et al., 2012b).
Greene et al. (2012b) proposed the following possible model for this early carbonate cementation:
as elevated atmospheric CO2 equilibrated with the ocean, it lowered pH within the water column;
subsequently, the upper portion of seafloor sediment became acidified followed by sulfate
reduction which caused an increase in pH at the sediment-water interface, promoting carbonate
precipitation. In addition, early diagenetic carbonate deposition could have been enhanced by local
anoxia and/or dysoxia through restrained dissolution causing oxic respiration and producing
alkalinity via anoxic remineralization (Higgins et al., 2009; Greene et al., 2012b). The paucity of
carbonate deposits across the mass extinction intervals such as the Schattwald Beds in Austria
(McRoberts et al., 2012; Hillebrandt et al., 2013) favor the ocean acidification scenario (Greene et
al., 2012a; Wignall and Atkinson, 2020). The selective nature of the extinction against acid-
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sensitive organisms such as aragonitic bivalves and corals conforms the presence of a
biocalcification crisis during the ETE (Kiessling et al., 2007; Kiessling and Aberhan, 2007;
Kiessling and Simpson, 2011; Greene et al., 2012a).
1.6. Dissertation purpose and significance
Emplacement of the Central Atlantic Magmatic Province is linked to the ETE yet killing
mechanisms and the sequence of events are still unclear. Significantly, the pre-extinction scenario
remains elusive limiting an accurate reconstruction of the events leading up to the ETE. The
purpose of this research is to elucidate the nature of biotic and environmental changes in different
parts of the Panthalassic and Tethys basins, with emphasis on aspects of sedimentology,
paleoecology and geochemistry during the lead up to the ETE. This study will address the
following outstanding questions:
1. Was the extinction pattern in the marine realm sudden or protracted? How did the
extinction pattern vary between Panthalassic and Tethys basins?
2. What were the paleoenvironmental and paleoecological trends that governed leading up to
the ETE across the basins? Are they associated with the earlier stages of CAMP
emplacement?
3. What role did euxinic/anoxic conditions play before and during the ETE? Did suboxic
conditions have any effect and to what extent on marine ecosystems?
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4. Was the “precursor” carbon cycle perturbation a global phenomenon? What is the temporal
correlation of the “precursor” to other biogeochemical and marine ecosystem changes in
Eastern Panthalassa?
5. What were the main triggers of the ETE and its effect on biotic turnover?
These questions have been addressed by investigating stratigraphic sections across
different depositional environments in Panthalassa and Tethys as well as data from the
Paleobiology Database (PBDB). Targeted sections include Ferguson Hill, Nevada (mid-outer
shelf, Eastern Panthalassa) (Chapter 2), Williston Lake, British Columbia, Canada (offshore to
lower shoreface, Northeastern Panthalassa) (Chapter 3) and the Northern Calcareous Alps, Austria
(intraplatform depression, Tethys) (Chapter 4) (Fig. 3). To evaluate a biotic turnover across the
globe during the Late Triassic to Lower Jurassic, faunal occurrences extracted from the PBDB
were also analyzed (Chapter 5).
In Chapter 2, work is presented which attempts to elucidate the pre-extinction conditions
leading up to the ETE through a high-resolution petrographic, faunal, and carbon isotope analyses
in association with Hg data of the upper Rhaetian strata at the Ferguson Hill locality in Nevada
(Fig. 3). The Ferguson Hill site is one of the best sections in the world to study the ETE as it has
been proposed as a Global boundary Stratotype Section and Point (GSSP) candidate multiple times
for the Triassic-Jurassic boundary (Guex et al., 1997; Lucas et al., 2007; McRoberts et al., 2007).
In addition, the Ferguson Hill site has well-established biostratigraphy, chemostratigraphy,
paleontological and paleoenvironmental data providing a robust framework for further studies
(e.g., Laws, 1982; Guex et al., 2004; Ward et al., 2007; Ritterbush et al., 2014; Corsetti et al., 2015;
Thibodeau et al., 2016). The Rhaetian Stage is represented by the carbonate ramp of the Mount
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Hyatt Member of the Gabbs Formation, which is overlain by the siliciclastic-dominated facies of
the Muller Canyon Member of the Gabbs Formation. The facies of the Muller Canyon Member
are interpreted as middle to inner shelf deposited between fair-weather and storm-weather wave
base (Laws, 1982; Lucas et al., 2007; Ritterbush et al., 2014; 2016).
For the first time, this research shows the “precursor” negative carbon isotope excursion
(“precursor” CIE) in eastern Panthalassa implying a truly global extent of the pre-extinction carbon
cycle perturbation (Fig. 2). Petrographic analysis reveals the presence of low oxygen sediments
co-occurring with a perturbation in the carbon cycle. The “precursor” CIE interval as well as
“initial” CIE is depauperate of macrofauna highlighting the detrimental effect of fluctuations in
the carbon cycle on shallow marine ecosystems. Sulphidic sediments overlap with the first
appearance of chemosymbiotic bivalves and low oxygen tolerant taxa illustrating a gradual change
to tolerance of dysoxic conditions by the benthic fauna. Episodic anoxic conditions initiated the
restructuring of the marine benthic community towards more low oxygen tolerant taxa and lower
diversity priming the marine ecosystem for global collapse during the main phase of CAMP
volcanism in the Eastern Panthalassa.
In Chapter 3, investigations are reported on uppermost Triassic phosphorites as a proxy for
deciphering paleoenvironmental conditions immediately preceding the ETE at Williston Lake,
British Columbia, Canada (Fig. 3). Exposures along Williston Lake span the Triassic/Jurassic
boundary including the record of the entire Rhaetian across different environments (Wignall et al.,
2007). The siliciclastic-carbonate sequences were deposited in a foreland basin on a distal slope
on the western side of the continental shelf of the supercontinent Pangea and subsequently shallow
upwards.
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This study examines the genesis of phosphorite deposits, predominately composed of
phosphatic coated grains, using petrographic analysis, Scanning Electron Microscopy (SEM) and
Raman spectroscopy. Raman spectroscopy reveals that phosphatic grains are composed of
carbonaceous material of biogenic origin while SEM and petrographic data uncover the presence
of putative microbial structures within phosphoclasts. Our study favors a mechanism of
phosphogenesis via microbial polyphosphate metabolism that implies transient euxinic conditions.
Presence of pyrite framboids within phosphorites is consistent with a euxinic scenario. Such
conditions were likely unfavorable for shallow water benthic metazoans making them more
vulnerable to subsequent effects from CAMP volcanism. This study presents the first shallow
marine record of episodic euxinia in northeastern Panthalassa that preceded the emplacement of
CAMP.
In Chapter 4, research is presented that addresses questions regarding extinction patterns
and paleoenvironmental trends leading up to the ETE in the Tethys basin and triggering
mechanisms that cause the major biotic collapse in the area. The Northern Calcareous Alps (NCA)
in Austria preserve one of the most complete marine sedimentary records of upper Rhaetian strata
in the world with the GSSP for the Triassic/Jurassic boundary located at Kuhjoch, Austria. A
detailed microfacies and macrofaunal study was conducted of five key sections including Kuhjoch,
Schlossengraben, Eiberg, Juifen and Restentalgraben located in the NCA, Austria (Fig. 3).
Macrofaunal and microfacies analyses of the upper Rhaetian strata elucidate the presence
of an ecologically diverse and robust marine benthic community across different depositional
environments all the way up-section to the main phase of CAMP volcanism. Based on the
documented faunal shifts and sedimentological analysis in the Tethys realm, we propose that the
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combination of reduced salinity, episodic suboxic conditions and ocean acidification caused the
abrupt ecological crisis during which eurytopic opportunistic paleocommunities flourished
followed by their demise during the main phase of the extinction as environmental conditions
worsened due to the main phase of CAMP volcanic activity. When extinction patterns are
compared between two basins, the Tethys experienced the sudden tempo of ecological changes in
contrast to the more protracted nature of ecological shifts recorded in the Panthalassa.
In Chapter 5, results are reported from an examination of the global geochemical record
and biotic changes on a stage-by-stage basis from the Carnian to Sinemurian. The Rhaetian Stage
is characterized by reduced generic richness in marine invertebrates across the globe implying an
important role of the biotic turnover and carbon cycle perturbation event that happened at the
Norian/Rhaetian boundary. The marine ecosystem in Panthalassa was more severely affected after
the ETE compared to the Tethys basin possibly due to unfavorable suboxic conditions before the
major onset of the extinction and protracted post-extinction recovery due to the “sponge takeover”
event.
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Figure 1. Generic diversity among major marine animal groups through the Phanerozoic. Adapted
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Figure 2. Summary of major geochemical, biotic and environmental perturbation events across
the Triassic/Jurassic (=T/J) boundary. Adapted from Zaffani et al. (2018).
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Figure 3. Late Triassic paleogeographic map showing studied localities and original extent of the
Central Atlantic Magmatic Province (CAMP).
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CHAPTER 2. ECOSYSTEM CHANGE AND CARBON CYCLE PERTURBATION
BEGAN BEFORE THE END-TRIASSIC MASS EXTINCTION
This paper is currently in revision for Earth and Planetary Science Letters as:
Larina, E., Bottjer, D. J., Corsetti, F. A., Thibodeau, A. M., Berelson, W. M., West, A. J.,
Yager, J. A. Ecosystem change and carbon cycle perturbation began before the end-Triassic
mass extinction. Earth and Planetary Science Letters. In Revision.
Abstract
During the Phanerozoic, global major upheavals in life history and the carbon cycle are
predominantly linked to the emplacement of Large Igneous Provinces, but the delineation of a
cause-effect framework remains unclear. The end-Triassic mass extinction (ETE) is temporally
associated with emplacement of the Central Atlantic Magmatic Province (CAMP). A better
understanding of precursor events to the ETE is essential if the mechanisms for this "Big 5" mass
extinction are to be fully delineated. Here, we present new high-resolution data integrating
petrographic, biotic, mercury, and carbon isotope analyses of the pre-extinction interval at the
Ferguson Hill locality, Nevada (USA). We document the “precursor” carbon isotope excursion
along with low Hg concentrations and sulphidic sediments prior to the ETE. A combination of
proxies reveals disruptions to shallow marine ecosystems and biogeochemical cycles prior to the
main phase of CAMP volcanism. We propose that episodic anoxic conditions restructured shallow
marine benthic ecosystems towards overall lower diversity including more low oxygen tolerant
taxa preceding the ETE. The timing of the initial marine ecosystem restructuring in Eastern
Panthalassa could be related to the early phase of CAMP emplacement and implies that an early
intrusive event initiated the ecosystem changes. These restructured marine ecosystems reflect the
deteriorating environmental conditions leading up to the ETE that ultimately resulted in the ETE.
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2.1. Introduction
Mass extinctions can be sudden or geologically protracted events, and an understanding of
environmental and ecological change proceeding them can provide important insights on
extinction mechanisms and consequences. Current understanding of the end-Triassic mass
extinction (ETE) is that it initiated as a geologically sudden event caused by the effects of large
igneous province (LIP) emplacement. However, little is known about the environmental or
ecological prelude to this "Big 5" mass extinction, particularly in marine environments. Here, we
provide a detailed paleoecological and paleoenvironmental analysis of strata deposited before the
onset of the ETE at one of the most complete marine Triassic-Jurassic sections in the world, at the
Ferguson Hill locality (Nevada, USA). This study provides further clarity on the environmental
stressors that acted in the lead-up to the ETE and their effect on marine ecosystems in eastern
Panthalassa.
2.2. Background.
2.2.1. End-Triassic mass extinction and carbon cycle disruptions.
The end-Triassic mass extinction (ETE) occurred ~201.51 million years ago and has long
been proposed to be caused by volcanic activity from the early break-up of the supercontinent
Pangea, which led to the formation of a LIP, the so-called Central Atlantic Magmatic Province
(CAMP) (e.g., Hesselbo et al., 2004; Schaller et al., 2012; Blackburn et al., 2013; Dal Corso et al.,
2014; Thibodeau et al., 2016; Lindström et al., 2021). Greenhouse gases derived from CAMP
basalts are generally favored as a major trigger for environmental changes and associated end-
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Triassic biotic loss (e.g., Pálfy and Kocsis, 2014; Thibodeau et al., 2016; Marzoli et al., 2018;
Zaffani et al., 2018). Abundant evidence points to a rapid rise in end-Triassic atmospheric CO2
that likely led to climate perturbations initiating global warming (e.g., Pálfy and Kocsis, 2014),
ocean acidification (e.g., Greene et al., 2012), and ocean anoxia (Jaraula et al., 2013; Atkinson and
Wignall, 2019; Fujisaki et al., 2020).
Carbon isotope records may provide some insight into the links between CAMP volcanism,
the rise in atmospheric CO2, and the extinction. Three negative carbon isotope excursions (CIEs),
called “main”, “initial”, and “precursor”, are documented globally in association with the
emplacement of CAMP. These are hypothesized to be related to multiple disruptions of the global
carbon cycle before and across the ETE (e.g., Thibodeau et al., 2016; Korte et al., 2019; Fujisaki
et al., 2018, 2020; Heimdal et al., 2020). The onset of the ETE coincides with the “initial” negative
carbon isotope excursion (ICIE) documented worldwide in terrestrial and marine environments
(Dal Corso et al., 2014; Yager et al., 2017; Korte et al., 2019; Ruhl et al., 2020). In marine settings,
the ICIE is concomitant with the last occurrence (LO) of the last Triassic ammonoids
Choristoceras crickmayi in North America and C. marshi in the Northern Calcareous Alps, as well
as radiolarian and dinoflagellate turnover (Zaffani et al., 2018)
providing a sophisticated
framework for a high precision correlation around the globe. Sources of
13
C-depleted carbon
release have been linked to (1) volcanic emissions from CAMP basalts (e.g., Dal Corso et al.,
2014; Pálfy and Kocsis, 2014; Thibodeau et al., 2016), (2) release of marine clathrates as a result
of warming climate (Korte et al., 2019), and (3) thermogenic methane derived from organic rich
sediments as a result of CAMP intrusive activity (Ruhl and Kürschner, 2011; Heimdal et al., 2020).
However, recent work (Fox et al., 2020) has argued that that putative negative organic carbon
isotope excursion in the Bristol Channel (UK) was in fact the result of transition from marine to
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nonmarine conditions, and specifically reflects the isotopic signature of microbial mats rather than
a massive input of isotopically light carbon derived from CAMP activity — emphasizing that
isotope excursions from sections that underwent significant changes in water depth and salinity
should be interpreted with particular caution. To what extent bio-sedimentological changes may
have influenced the end-Triassic isotope records at other locations remains unclear, though the
global extent of the ICIE, and its coincidence with CAMP activity, suggest plausible (indeed
likely) links between the two.
Models of the end-Triassic carbon cycle suggest that the release of
13
C-depleted carbon
solely from CAMP volcanic degassing is insufficient to account for the negative carbon isotope
anomalies (Paris et al., 2012; Bachan and Payne, 2016; Heimdal et al., 2020). Recent studies
advocate that thermogenic carbon degassing of volatile-rich sediments by dike and sill intrusions
in Brazil (Amazonas sill) is the primary contributor to perturbation of the global carbon cycle
which drove the extinction, suggesting an important role for CAMP intrusive rather than extrusive
activity during the ETE (Davies et al., 2017; Heimdal et al., 2020).
The intricacy of the end-Triassic carbon cycle story is further complicated by a precursor
carbon isotope excursion (precursor CIE) documented in a few shallow marine sections in the
Tethys Ocean (Hesselbo et al., 2004; Ruhl and Kürschner, 2011; Dal Corso et al., 2014; Bottini et
al., 2016; Zaffani et al., 2018) and in one deep marine section in the mid-Panthalassic Ocean
(Fujisaki et al., 2020)
(Fig. 1). This “precursor” CIE is of shorter duration and smaller magnitude
(~1-3‰) compared to the ICIE but hints at the disruption of the ocean-atmosphere carbon pool
prior to the ETE, albeit of smaller magnitude than during the ICIE (Ruhl and Kürschner, 2011;
Korte et al., 2019). Yet it remains unclear whether this precursor event is truly global in extent,
and the consequences of this early carbon cycle perturbation on marine ecosystems have not been
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explored. Fox et al., 2020, provide an alternative view of the St. Audrey’s Bay section where the
precursor event was first named, and as a result the St. Audrey’s Bay locality is excluded from the
sites with previously documented precursor CIE in our discussion (for further discussion see
Supplementary Material). In this study, we add new evidence from the Ferguson Hill locality in
Nevada, USA, shedding light on the elusive precursor CIE in Panthalassa and allowing us to
connect the pre-extinction carbon isotope records with biotic disruption in the marine realm.
2.2.2. Geological, paleoenvironmental and paleoecological setting
The Ferguson Hill locality (Fig. 1-3) is a part of the Gabbs Valley Range in Nevada that
represents one of the most complete marine records of Triassic-Jurassic sequences (Guex et al.,
1997; McRoberts et al., 2007; Korte et al., 2019). It was considered the second-best section in the
world to study the ETE when the Global Stratotype Section and Point (GSSP) for the Triassic-
Jurassic boundary was established (McRoberts et al., 2007). The Ferguson Hill section was
deposited in a back-arc basin bordered by the Sierran volcanic arc to the west and the North
American continent to the east (e.g., Lucas et al., 2007; Corsetti et al., 2015). The upper Rhaetian
Stage is represented by a carbonate ramp forming the Mount Hyatt Member (MHM) of the Gabbs
Formation, which is overlain by the siliciclastic-dominated facies of the Muller Canyon Member
(MCM). This sequence was likely deposited on a narrow shelf with a relatively steep slope along
the back-arc seaway (Corsetti et al., 2015).
The studied section is composed of thinly bedded to massive fine-grained calcareous
siltstone with occasional beds of silty sandstone primarily within the MCM (Fig. 3). Resistant
calcareous siltstone beds are mainly present within the uppermost MHM while the lowermost
MCM is characterized by an increase in siliciclastic grains where indurated beds contain parallel
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laminations (Fig. 4A) and small-scale cross-stratification features. Although there is no agreement
between studies on the existence and/or nature of possible sea-level changes during deposition of
the uppermost Rhaetian sequence, with arguments varying from regression (Laws, 1982; Lucas et
al., 2007) to transgression (Hallam and Wignall, 2000) during this interval, the depositional
environment is consistently interpreted as middle to inner shelf deposited below fair-weather and
near storm-weather wave base (Laws, 1982; Lucas et al., 2007; Corsetti et al., 2015; Ritterbush et
al., 2014). No substantial facies change or unconformities were observed across the studied section
suggesting continuous sedimentation and allowing an examination of uninterrupted rock record
right before and across the end-Triassic mass extinction (Lucas et al., 2007).
Laws (1982) performed a detailed faunal analysis of the entire Rhaetian sequence in west-
central Nevada and defined macrofaunal associations across the Gabbs Formation. According to
Laws (1982), the Tutcheria association is the most diverse assemblage from the Gabbs Formation,
with 25 species. The overlying Nuculoma association contains 11 species, where Nuculoma sp. is
the most abundant species and it appears for the first time ~7 m below the extinction horizon (Fig.
3H) (Laws, 1982).
The N3 bed within the lower MCM marks the onset of the end-Triassic mass extinction
based on the last occurrence of the last Triassic ammonoid Choristoceras crickmayi (this study
and Lucas et al., 2007), the record of the ICIE (this study; Ward et al., 2007; Corsetti et al., 2015;
Thibodeau et al., 2016) and an increase in Hg levels (Fig. 2). The interval between the base of the
N3 bed and MHM and MCM boundary differs by different studies from one to two meters. In our
stratigraphic section, the interval between the base of the N3 bed and the top of the MHM is one
meter which is consistent with the stratigraphic section published by Lucas et al. (2007; Fig. 7) for
the GSSP proposal. The discrepancy in measurements could be attributed to the gradational nature
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of sediments from the calcareous-rich Mount Hyatt to the more siliciclastic-rich Muller Canyon
Member (Ward et al., 2007), as well as seafloor topography, since different authors have measured
different sections across Ferguson Hill, and also to faulting in the area (Guex et al., 2009).
Sill intrusions of Cretaceous age cut across the Mount Hyatt Member at Ferguson Hill,
including a sill intrusion below the studied section. This resulted in “minimal” metamorphism of
the upper Rhaetian sediments in the area, based on a conodont alteration index of 3-5 (Orchard et
al., 2007; Lucas et al., 2007). Although there is light metamorphism, the Ferguson Hill section
appears to record mainly unaltered geochemical signatures based on the reproducibility of results
for Hg and carbon isotopes when compared with other studies at Ferguson Hill (Fig. 2) (Ward et
al., 2007; Corsetti et al., 2015; Thibodeau et al., 2016) and the consistency of our geochemical (Hg
and δ
13
Corg) record with that from Triassic/Jurassic sections across the globe (e.g., Davies et al.,
2017; Percival et al., 2017; Zaffani et al., 2018; Fujisaki et al., 2018; Ruhl et al., 2020; Lindström
et al., 2021).
2.3. Materials and Methods
The studied section was trenched down as much as 1m until unweathered bedrock was
uncovered. Rock samples were collected from this unweathered bedrock based on visual
inspection. Samples for geochemical (total of 64 samples) and petrographic analysis (total of 73
thin sections) were collected every 5 to 10 cm within the upper 4 m and every 20 to 25 cm within
the lower 4 m of the section.
2.3.1. Carbon isotope, carbonate and organic carbon measurements
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Samples with veins and surficial weathering were excluded from isotopic analysis. We
used an Elemental Analyzer (Costech) and Automate auto-sampler coupled to a Picarro Cavity
Ring Down spectrometer (G2131-i) for organic and inorganic carbon isotopes (δ
13
Corg and δ
13
Ccarb,
respectively), weight percent carbonate (%CARB), and weight percent organic carbon (%TOC)
measurements following the procedure from Yager et al. (2017). For δ
13
Ccarb, 1.2 mg of dried
ground powder was placed into glass vials with rubber septa caps (“exetainer” vials). Each vial
was evacuated to less than 1 torr followed by manual injection with 3 mL of 30% phosphoric acid.
Each vial was then heated for 90 minutes at 70°C. For organic carbon isotopes, carbonate was first
removed (“decarbonation”) utilizing 1 gram of ground powder and 40 mL of 1M HCl, placed in
70°C water for 4 hours in order to remove all carbonate phases. After heating, each sample was
rinsed three times with deionized water. Samples were then dried in the oven at 55°C. The isotopic
composition of carbon was obtained via the Picarro analyzer and results are reported relative to
the Vienna Pee Dee Belemnite standard. The uncertainty on the δ
13
Corg values was assessed from
replicate runs of standards (USGS 40 and internal carbonate standards) and samples. In order to
account for uncertainties, 33% of samples were replicated (see discussion in Subhas et al., 2015).
Standard deviation between samples and replicates is on average <0.05‰ (Table S1).
2.3.2. Petrographic analysis
Petrographic analysis reveals that the Ferguson Hill section is mainly composed of
interbedded calcareous siltstone beds with variation in carbonate percentage. Each thin section
was analyzed under a cathodoluminescent microscope (Nuclide ELM-3R Luminoscope) in order
to evaluate the degree of diagenesis of each sample (Fig. S1). Only a low to moderate degree of
cathodoluminescence was documented, suggesting minimal diagenesis across the studied section
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(Hiatt and Pufahl, 2014). A point-counting method was applied to determine the percentage of
bioclasts, goethite, clastic grains, Fe-stained cement, carbonate cement and the category “other”
in each thin section (Table S2). Counts of 100 points per each slide were implemented at random
increments.
2.3.3. Mercury measurements
Total mercury was measured using a Tri-Cell DMA-80 Direct Mercury Analyzer
(Milestone, Inc.) at Dickinson College. The instrument was calibrated using a gravimetrically
prepared Hg standard (made by diluting a commercially available ICP standard from Sigma
Aldrich) in a 0.25% L-cysteine solution. Blank measurements were periodically made to ensure
there was no significant carry over between samples and blank signals were less than 2% of typical
sample signals. To ensure measurement accuracy, NIST SRM 1545A (Trace Elements in Pine
Needles) was analyzed throughout each measurement session. Over all sessions, the average value
of NIST SRM 1545A was 40.4 ± 5.5 ppb (2 s.d., n = 18), which overlaps with the certified value
of 39.9 ± 0.9 ppb. Based on the reproducibility of samples and NIST SRM 1575A, we estimate
the uncertainty on the Hg concentration measurements to be between 10–15%.
2.3.4. Paleoecological analysis
A total of 12 bulk samples (9-11 L) were collected at intervals of interest. Each bulk sample
was disintegrated manually into rock fragments of ~1 cm
3
. Faunal specimens were identified to
the most precise taxonomic level possible. Intervals where bulk data is not reported were
extensively sampled in order to maximize sample size in addition to bulk samples. Specifically,
the interval between -1 and 1.6 m, where fossils are rare, was inspected thoroughly with total
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volume of rock processed at each horizon exceeding 15 L. The number of bivalve individuals for
a given species were estimated based on the number of articulated shells and the dominating
number of either dorsal or ventral valves (Gilinsky and Bennington, 1994). In the lower part of the
section, shells are often recrystallized and occasionally are preserved with original shell as
observed in thin sections (Fig. 4E). In the upper part of the section, macrofossils are predominantly
preserved as molds. Our dataset is composed of bivalves and cephalopods with crinoidal debris
observed in thin sections. Paleoecological traits such as tiering, feeding mode and degree of
motility were assigned to fossil specimens following Bambach (1983) and Bush et al. (2007).
Cluster analysis was performed on the species-abundance matrix in order to identify which
taxa co-occur allowing differentiation between assemblages based on faunal composition. Barren
samples and unidentified specimens were excluded from the cluster analysis, resulting in 241
identifiable individuals belonging to 14 taxa. The Bray-Curtis distance matrix and Ward’s method
for the most compact linkage (McCune and Grace, 2002) were used during cluster analysis. The
analysis was performed using the R package ‘cluster’ version 2.2.1 (Maechler et al., 2021) and the
R package ‘sparcl’ version 1.0.4 (Witten and Tibshirani, 2018).
2.4. Results
2.4.1. Carbon isotopes and organic carbon
Two negative carbon isotope excursions have been identified at the studied section. The
“initial” negative carbon isotope excursion of 1.7‰ is documented at the base of the N3 bed which
coincides with the last occurrence of Choristoceras crickmayi (Fig. 2, 3). Our d
13
Corg values and
placement of the ICIE are consistent with other independent studies at the Ferguson Hill locality
(Ward et al., 2007; Corsetti et al., 2015; Thibodeau et al., 2016) (Fig. 2) and this data point is
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correlative with other sections around the globe, including the GSSP for the Triassic/Jurassic
boundary Kuhjoch section, Austria (e.g., Hillebrandt et al., 2013; Ruhl et al., 2020). Another record
of carbon isotope stratigraphy at Ferguson Hill was documented by Guex et al. (2004). However,
the Guex et al. (2004) carbon isotope record differs from other studies, likely due to a different
methodology during the de-carbonation procedure which did not fully remove all carbonate,
including siderite and dolomite (see Ward et al., 2007 for further explanation). Since the data of
Guex et al. (2004) are not comparable with this or other studies in the area and their methodology
was questioned (Ward et al., 2007), we will not discuss further their data though we recognize
their pioneering contribution to the carbon isotope stratigraphy in the area.
The second largest negative CIE of 1.6‰, of short duration and of similar magnitude as
the ICIE, is documented ~6m below the ICIE between -5.95 and -5.4 m (Fig. 3). Based on the
magnitude of the excursion and its placement below the ICIE, we regard this deviation in d
13
Corg
values as the “precursor” carbon isotope excursion. Our placement of the “precursor” CIE
correlates with other “precursor” records documented in Tethys and Mid-Panthalassa (Fig. 1)
(Ruhl and Kürschner, 2011; Bottini et al., 2016; Zaffani et al., 2018; Fujisaki et al., 2018, 2020).
Our study documents the “precursor” CIE in Eastern Panthalassa for the first time confirming the
global phenomenon of carbon cycle perturbation preceding the ETE (Fig. 1, 3C).
Thermal heating of sediments from the underlying Cretaceous sill intrusion could
potentially impact the geochemical signature of these sedimentary rocks by affecting the maturity
of sedimentary organic matter and by preferential removal of certain compounds or particles from
the sediments (Deenen et al., 2010). In the studied section, total organic carbon (TOC)
concentrations are generally below 0.5% (Fig. 3, S2; Table S1) and do not show systematic change
or variation towards proximity to the sill, located a few meters below the studied section (Fig. 3,
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S2). Typically, when affected by heating, d
13
Corg values and TOC% are negatively correlated,
whereas the data from our section are not correlated (R
2
= 0.16), supporting a more primary
geochemical signature (Fig. 5A). In addition, reproducible carbon isotopes have been reported
from multiple studies in the area, although samples for these studies were collected at different
places across the Ferguson Hill area. In these studies, the documented carbon isotope excursions
are consistent with other end-Triassic carbon isotope records across the globe. Thus, we infer that
carbon isotope shifts found at Ferguson Hill represent a genuine record of changes in global carbon
reservoirs.
2.4.2. Petrographic investigation
Petrographic analysis reveals that the section is mainly composed of interbedded
calcareous siltstone beds with variation in carbonate percentage. The lowermost meter of the MCM
differs from beds below and above by an increased amount of sand and silt where beds are thinly
bedded to laminated (Fig. 4A) with small-scale ripple cross-laminations occasionally preserved.
Microfacies analysis reveals the presence of iron-hydroxides (mainly goethite) (Fig. 4C-
E), which are frequently found as an oxidation product of different types of pyrite (Soliman and
Goresy, 2012; Keller et al., 2020) and typically indicate the former presence of sulphide minerals
after the sulphur was stripped during alteration. Original pyrite morphology (framboids, square
shapes) is occasionally observed in thin sections corroborating the initial mineral phase as pyrite
(Fig. 6D-E).
In thin section the goethite commonly has a framboidal habit (Fig. 4C), suggesting a pyrite
precursor. The first increase in goethite (between 11% to 15%) is documented between -5.85 and
-5.5 m. This interval coincides with the “precursor” CIE (Fig. 3). Between -1.8 to -0.10 m there
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are episodic increases in the amount of goethite, with peaks ranging between 10% to 25%. Starting
at 0.3m, the concentration of goethite is consistently high, from 8% to 23%. Presence of pyrite
(reflected by the goethite pseudomorphs) suggests anoxic and sulphidic conditions within the
sediment and potentially the water column (Wilkin et al., 1996). This interpretation is supported
by the depauperate benthic community and absent to minimal bioturbation starting at 0.1m and up
(Fig. 4A).
2.4.3. Hg concentrations
Hg concentrations normalized to TOC have commonly been used as a proxy for LIP
volcanism in sedimentary successions (e.g., Percival et al., 2017; Them II et al., 2019; Charbonnier
et al., 2020; Keller et al., 2020; Lindström et al., 2021). In the studied section, the MHM and MCM
contain low organic carbon concentrations (TOC < 0.5%) (Table S1) that are decoupled from total
Hg content (Fig. 3E, 5B, D, F). This decoupling implies a negligible effect on total Hg
concentrations by organic carbon loading and different supply sources for Hg and organic carbon
into the sediments (Thibodeau et al., 2016). Because TOC is low throughout the section, we discuss
Hg concentrations instead of Hg/TOC ratios, although both curves have similar shapes (Fig. 3E).
Mercury concentrations remain below 21 parts per billion (ppb) from the bottom of the
section up to -1m, followed by a short-lived excursion up to 49 ppb at -0.8m (Fig. 3D). A second
rise in Hg starts at 0.6m and persists up the section. Mercury enrichment co-occurs with increased
presence of goethite (as a proxy for sulphide) in the upper part of the section (~1-1.5m), but no Hg
enrichment is seen lower in the section, where increased framboid/sulphide abundance is
associated with the “precursor” CIE (Fig. 3).
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2.4.4. Paleoecology
The faunal composition of our studied interval at Ferguson Hill consists of 8 bivalve
species, 4 species/2 genera of ammonoids, 1 belemnoid species, and 1 nautiloid (Fig. 3G). Crinoid
ossicles are observed in one hand sample and are more common in thin sections. Six categories of
life mode are detected at Ferguson Hill leading up to the ETE with the most abundant mode of life
represented by mobile deposit suspension feeding epifauna (Fig. 3G). The epifaunal mobile
deposit suspension feeding mode of life is mainly represented by the relatively high abundance of
the nuculanid bivalve Nuculoma sp. This faunal distribution is consistent with the previous study
of faunal assemblages in the area documented by Laws (1982). In particular, our studied section
is entirely within the Nuculoma association range (Fig. 3H) identified by Laws (1982).
The last occurrence of the last Triassic ammonoid Choristoceras crickmayi is documented
at the base of the N3 bed, which is marked by the ICIE and has been associated with the onset of
CAMP volcanism in past studies (Corsetti et al., 2015; Thibodeau et al., 2016) (Fig. 2, 3, 6B).
With the exception of C. crickmayi, all macrofossils disappear right below the N3 bed. Similarly,
the interval spanning the “precursor” CIE from -6 to -5 m is depauperate of macrofauna (Fig. 3).
We document a decline in faunal abundance and diversity above -1 m in association with an
increased percentage of goethite and the first peak of Hg concentrations (Fig. 3).
For the first time at Ferguson Hill, we report the lowest appearance of the lucinid bivalve
Mesomiltha sp. and the appearance of Astarte sp. in association with an increased abundance of
Nuculoma sp., 4 m below the extinction interval (Fig. 3). Lucinids are chemosymbiotic bivalves
that require both sulphide-rich anaerobic sediments in order to provide nutrients for sulphur-
oxidizing symbionts and oxygen from the overlying seawater. As a result, their habitat is restricted
to environments that allow lucinids to colonize sediments where the redox boundary is relatively
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close to or at the sediment surface (Bottjer et al., 1995; Distel, 1998). Nuculoma sp. is a
protobranch bivalve of the family Nuculidae which is known to tolerate hypoxic conditions
(Holmes et al., 2002). An extant relative of Astarte sp., Astarte borealis, can survive in acute
hypoxic condition for over 32 weeks (Vaquer-Sunyer and Duarte, 2008).
Occurrence of lucinids, nuculanids and astartids across the uppermost carbonate-rich
MHM and the lowermost silica-rich MCM suggest a weak facies control on faunal distribution.
Periodic sulphidic conditions within the sediment are corroborated by the pulsed nature of
increased goethite percentage across the section (Fig. 3). Overall progression up-section in the
MHM from the diverse Tutcheria association (Laws, 1982) (Fig. 3H), indicative of well-
oxygenated environments, to the less diverse Nuculoma association (Fig. 3G,H), with its
increasing composition of low-oxygen tolerant taxa, to the lack of macrofauna in the overlying N3
bed (and the ETE) (Fig. 3G,H), is reminiscent of the classic aerobic-dysaerobic-anaerobic
biofacies trend from well-oxygenated to anoxic environments (Savrda and Bottjer, 1991).
Cluster analysis reveals faunal co-occurrence of Nuculana sp. and Mesomiltha sp. with
Chlamys sp. (cluster B; Fig. 6A). The pectinid bivalve Chlamys sp. is the second most common
bivalve in the section characterized by a stationary suspension feeding epifaunal mode of life.
Chlamys is a widespread generalist bivalve that is commonly present in pre- and post- extinction
intervals of sections with the ETE (Ward et al., 2007; Lucas et al., 2007; Hillebrandt et al., 2013).
2.5. Discussion and Conclusions.
The presence of the “precursor” CIEs in different regions of Tethys and Panthalassa adds
to a growing body of evidence indicating that environmental conditions began to deteriorate well
before the initial phase of CAMP eruptions (e.g., Davies et al., 2017; Yager et al., 2017; Lindström
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et al., 2021), suggesting that earlier intrusive phases of CAMP activity may have contributed to
the ETE (Davies et al., 2017). The source of the “precursor”
13
C-depleted carbon is still under
debate (Ruhl and Kürschner, 2011; Marzoli et al., 2018; Heimdal et al., 2020), but the carbon could
have been released either from early CAMP basaltic eruptions discovered in the High Atlas
(Morocco) (Dal Corso et al., 2014) or from intrusive CAMP activity into organic-rich sediments
(Zaffani et al, 2018; Heimdal et al., 2020). To this date, the oldest known CAMP magmatic
intrusion is the Kakoulima intrusion located in Guinea and dated at 201.635 ± 0.029 Ma (Davies
et al., 2017)
(Fig. 3A). The Kakoulima intrusion is closely followed by the Messejana dyke in
Spain and the Tarabuco mafic sill in Bolivia, constituting the early phase of CAMP emplacement
(Davies et al., 2017; Heimdal et al., 2020). Degassing from these deep metasomatised rocks is
unresolved (Davies et al., 2017), but their close temporal correlation with the “precursor” CIE
suggests they could have driven the release of the
13
C-depleted carbon. This idea was first put
forward by Davies et al. (2017), who recognized geochemical and biotic changes preceding the
ETE and linked these to new high-precision U-Pb ages from CAMP intrusive units. Lindström et
al. (2021) suggest that the “precursor” CIE could be related to undated CAMP extrusives or
intrusives. Overall, most studies are in agreement that carbon cycle fluctuations before the onset
of the ETE are related to CAMP emplacement, yet the precise mechanism and timing is yet to be
determined.
To our knowledge, no previous study has attempted an integrative analysis of geochemical,
petrographic and marine faunal distribution across the “precursor” and up to the ETE interval.
Based on the marine benthic macrofaunal distribution, we infer that shallow marine benthic
ecosystems were under stress leading up to the ETE, at least in Eastern Panthalassa. More studies
are required to further resolve the spatial and temporal conditions leading up to the end-Triassic
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mass extinction event.
The lowermost part of the studied section up to – 3 m is characterized by low abundance
and diversity (Fig. 3G). Such a distribution is possibly the result of atmospheric perturbations
related to the “precursor” CIE coupled with anoxic/sulphidic sediments documented at the base of
the section (Fig. 3F). The most diverse and abundant interval is documented between – 3 and -1 m
(Fig. 3G). The middle part of the section is characterized by the first appearance of
chemosymbiotic lucinids (Mesomiltha sp.) and low oxygen tolerant taxa (Astarte sp.) as well as
Nuculoma sp., illustrating a gradual change to tolerance of dysoxic conditions by the benthic fauna
where three out of eight documented bivalves are commonly associated with hypoxic conditions.
Up to -1 m, episodic deoxygenation was probably short-lived as indicated by the mix in samples
of taxa requiring normal oxygen conditions as well as taxa capable of living in low oxygen
environments.
Faunal abundance and diversity decrease above -1 m with no evidence for significant
lithological change across this interval. Based on the consistently high goethite percentages in the
upper part of the section, it appears that suboxic conditions intensified immediately before and
across the ETE (Fig. 3F). Photic zone euxinia and fluctuating euxinic/anoxic conditions preceding
the ETE are also documented in northeastern Panthalassa suggesting that suboxic conditions were
widespread in the Panthalassic basin leading up to the ETE (Kasprak et al., 2015; Larina et al.,
2019). Modern examples of episodic hypoxic events in the Gulf of Trieste show that even when
hypoxia lasts only for a few days or weeks, it takes years or decades for benthic communities to
recover (Tomašových et al., 2017) signifying a stressed environment for marine ecosystems even
during punctuated hypoxia. The presence of lucinids would have occurred due to deoxygenation
events that would have caused the redox zone to rise towards the seafloor, within reach of the
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burrowing lucinids, which could also then respire from the at least somewhat oxygenated overlying
seawater. Intervals with suitable seawater oxygen content would have facilitated the survivorship
of benthic fauna such as the generalist Chlamys sp. occurring in the upper part of the section (Fig.
3G).
Mercury has been widely used as a proxy for LIP volcanism in sedimentary successions
that record extinctions and ecological crises (e.g., Thibodeau et al., 2016; Percival et al., 2017;
Keller et al., 2020; Lindström et al., 2021). However, interpretations of the mercury record can be
difficult as the primary signal may be obscured or altered by different depositional environments,
organic matter degradation and delivery, metal cycling, proximity to the shore, and redox
variability, among other factors (e.g., Grasby et al., 2019; Them II et al., 2019; Yager et al., 2019).
Thus, Hg records must be interpreted with caution.
The Hg record presented here is consistent with previously published Hg data from
Thibodeau et al. (2016) at Ferguson Hill (Fig. 2). However, due to high-resolution sampling, we
are able to identify several short-lived Hg peaks before the extinction interval. In the lower part of
the section, Hg levels are low and no increase in Hg is associated with the “precursor” CIE interval.
The earliest substantial Hg peak spans a short interval between -0.8 and -0.6 m (Fig. 2, 3), followed
by a rise in Hg levels that appears at 0.6 m (about 0.5 m below the ETE) and persists up the section.
If these Hg peaks (which are modest in magnitude) are interpreted as evidence of CAMP
volcanism, they add to the evidence that the onset of CAMP volcanism preceded the “initial”
carbon cycle perturbation and the ETE (Dal Corso et al., 2014; Marzoli et al., 2018; Lindström et
al., 2019) but occurred well after the “precursor” event. Further, evidence for Hg cycle
perturbations preceding the ETE are in accordance with the records at the Stenlille-1 and Norra
Albert/Albert-1 sites in northwestern Europe (Lindström et al., 2019, 2021).
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The interpretation of these Hg peaks is complicated by evidence for pyrite deposition,
particularly in the upper part of the section (Fig. 3D). Like organic carbon, sulphide minerals can
scavenge Hg (Wolfenden et al., 2005; Them II et al., 2019; Shen et al., 2020), and an increase in
sulphide/pyrite formation would enhance the sink for Hg in marine sediments (Wolfenden et al.,
2005). Further, it is possible that the alteration of sulphides to iron oxides could impact any Hg
originally associated with sulphide phases (Keller et al., 2020). Although it is possible that the
elevated Hg levels leading up to the ICIE could result from increased scavenging by sulphide,
there is no obvious increase in Hg during the “precursor” CIE, despite evidence for sulphide
formation during this period. This contrast supports the interpretation that sediments in the interval
leading up to the ICIE might have been subject to increased Hg loading.
After a short-lived recovery between -3 and -1m, a second drop in macrofaunal abundance
and diversity is documented above that is coincident with an increase in Hg concentrations and
sulphidic sediments (Fig. 3) suggesting a cause-effect relationships between the abundance of
benthic organisms and associated sulphidic sediments. Disturbance of benthic ecosystems above -
0.8 m could be related to the combination of environmental stress from episodic anoxia and
CAMP-related environmental and biogeochemical perturbations associated with the atmosphere-
ocean pollution caused by CAMP-derived volcanic gasses (e.g., Davies et al., 2017). A
documented decline in terrestrial vegetation in western Greenland and bivalve diversity in the
United Kingdom before the onset of the ETE (Van de Schootbrugge e tal., 2009; Mander et al.,
2010; Davies et al., 2017) implies the presence of environmental perturbations in the marine and
terrestrial realm across the globe. Although the low oxygen taxa were resilient during intervals of
episodic anoxia in eastern Panthalassa before the onset of the ETE, the combination of ETE related
causes such as longer-term anoxia, ocean acidification, and global warming likely gave a final
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blow to this marine benthic community (e.g., Greene et al., 2012; Fujisaki et al., 2018; Larina et
al., 2019; Lindström et al., 2021).
We suggest that the early phase of CAMP emplacement perturbed the global carbon cycle
and initiated shallow marine ecosystem restructuring towards lower diversity associations that
included low oxygen tolerant taxa in eastern Panthalassa. These ecosystem changes reflect the
deteriorating conditions which ultimately resulted in decisive ecosystem collapse during the main
phase of CAMP extrusive volcanism that resulted in the ETE.
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Figure 1. Lower Jurassic paleogeographic map showing sites with the documented precursor
carbon isotope excursion (precursor CIE). 1 = Ferguson Hill, USA (this study, 38°29'13.21"N
118° 5'2.34"W); 2 = Eiberg, Austria
(Ruhl and Kürschner, 2011); 3 = Wüstenwelsberg, Germany
(Ruhl and Kürschner, 2011); 4 = Lombardy, Italy
(Zaffani et al., 2018); 5 = Katsuyama, Japan
(Fujisaki et al., 2020). The map is modified from Greene et al. (2012).
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Figure 2. Composite stratigraphic section from Ferguson Hill, Muller Canyon, Nevada from
Thibodeau et al.
(2016)
and this study. The base of the extinction interval (bed N3 in Lucas et al.,
2007) is defined by the last occurrence of the last Triassic ammonoid Choristoceras crickmayi (=
C. crickmayi) and coincides with the initial carbon isotope excursion (ICIE) documented
worldwide as well as a rise in Hg of volcanic origin marking the onset of CAMP extrusive
volcanism
(Thibodeau et al., 2016). The extinction interval comprises 7m of siliciclastic siltstone
where shelly remains drop to practically undetectable levels and is overlain by 9m of the so-called
depauperate interval (Corsetti et al., 2015). Mercury levels remain elevated through the extinction
and depauperate intervals, suggesting that biota did not begin to fully recover until the CAMP
eruptions ceased
(Thibodeau et al., 2016). Though these broad trends are known, the detailed
geochemical and biotic changes in the leadup to the ETE at this site are not. The data from this
study is depicted in blue and from Thibodeau et al. (2016) is depicted in black. The data from
Ward et al. (2007) is depicted in orange and placement of carbon isotopes from Ward et al. (2007)
is adjusted in accordance with faulting record in Guex et al. (2009). Red line shows dated ash bed
from Ferguson Hill by Schoene et al. (2010). Dates for C. crickmayi and Psiloceras spelae (=P.
spelae) are from Wotzlaw
et al. (2014).
Figure modified from Thibodeau et al.
(2016).
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Figure 3. Stratigraphic section of the studied site showing macrofaunal, geochemical and
petrographic data. ETE = the end-Triassic mass extinction event. Cc = Choristoceras crickmayi.
A. Stratigraphic log of the studied section B. Ticks mark horizons of examined thin-sections. MF
= microfacies. C. Organic carbon isotope record from this study. D. Total organic cabon (TOC)
percent from this study. E. Mercury measurements and Hg/TOC data from this study. F.
Percentage of goethite as observed in thin sections. G. Macrofaunal distribution of bivalves and
cephalopods. Low oxygen tolerant taxa is highlighted in light brown. Circle size corresponds to
number of specimens identified at this horizon. Color of a circle corresponds to mode of life. H.
Total species diversity across faunal associations defined by Laws (1982) including Nuculoma
sp. range as documented by Laws (1982).
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Figure 4. A. Parallel laminations observed in the lowermost part of the Muller Canyon Member.
B. Overview of the Ferguson Hill site. Black box shows the position of the studied site at the
Ferguson Hill. C. Black arrows point to examples of sulphide pseudomorphs. The image is in
50 µm
A B
C D
E F
100 µm
100 µm
40 µm
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plane-polarized light. D. Thin-section showing bivalve shell replaced with goethite. The image is
in plane-polarized light, collected at -18 cm. E. Thin-section showing cubic shaped goethite
replaced after pyrite within the unaltered bivalve shell. The image is in plane-polarized light,
collected at -30 cm. F. Thin-section showing cubic shaped goethite replaced after pyrite. The
image is in cross-polarized light, collected at 8 cm.
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A
B C
all data all data
D
pre-extinction
E
pre-extinction
F
extinction
G
extinction
Goethite (%) Goethite (%) Goethite (%)
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Figure 5. A. Plot of organic carbon isotope values versus total organic carbon percent showing no
good correlation between the two data sets for Ferguson Hill section. B. Plot of total organic carbon
percent (TOC %) versus Hg concentrations (Hg ppb) for the Ferguson Hill section for all data
points. C. Plots of goethite percent versus Hg concentrations (Hg ppb) for the Ferguson Hill section
for all data points. D. Plot of total organic carbon percent (TOC %) versus Hg concentrations (Hg
ppb) for the Ferguson Hill section for only pre-extinction interval. E. Plots of goethite percent
versus Hg concentrations (Hg ppb) for the Ferguson Hill section for pre-extinction interval. F.
Plot of total organic carbon percent (TOC %) versus Hg concentrations (Hg ppb) for the Ferguson
Hill section for extinction interval. G. Plots of goethite percent versus Hg concentrations (Hg ppb)
for the Ferguson Hill section for pre-extinction interval.
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Figure 6. A. Bray-Curtis similarity cluster analysis of macrofaunal assemblage of the studied
section. B. Choristoceras crickmayi found at the base of the N3 bed (1.1 m). Specimen number
LACMIP 42924.1 (type 14856). C. Mesomiltha sp. found at -1.0 m. Specimen number LACMIP
42925.1 (type 14857) D. Nuculoma sp. found at -1.2 m. Specimen number LACMIP 42926.1
(type 14858). Scale = 1 cm.
A
B
C D
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S1. Additional background on timing, magnitude, and global correlation of negative carbon
isotope excursions before and across the end-Triassic mass extinction
The correlation of CIEs in different sites around the globe is mainly based on bio-,
magneto-, and chemo- stratigraphy, and faunal and floral turnover events (Zaffani et al., 2018).
Initial CIE. - The initial negative carbon isotope excursion (ICIE) is of short duration and is closely
followed by a positive CIE (Fig. 2). The magnitude of the ICIE varies between the Panthalassic
and Tethyan basins with 1.5-3‰ in d
13
Corg in eastern Panthalassa (Thibodeau et al., 2016; Yager
et al., 2017; Ruhl et al., 2020) and 4-6.5‰ in d
13
Corg in Tethys (Ruhl et al., 2020). These differences
have been attributed to extreme aridity across the western Pangean landmass causing lower
delivery of organic carbon to the Panthalassic continental shelf compared to a humid climate across
the central Pangean landmass (Bonis et al., 2010; Ruhl et al., 2020).
Precursor CIE. - Originally, the precursor CIE was documented at St. Audrey’s Bay by
Hesselbo et al. (2002, 2004), although it was not interpreted as such. Later Ruhl and Kürschner
(2011) proposed the first negative carbon isotope excursion below the ICIE as a “precursor” CIE
within the Westbury Formation at St. Audrey’s Bay. The current placement and interpretation of
“precursor” and “initial” CIE at St. Audrey’s Bay should be investigated further before using this
section as a reference for global correlation of carbon isotope records. First, because the current
widely used placement of the ICIE at St. Audrey’s Bay is dubious and reflects the isotopic
signature of regionally occurring microbial mats rather than a global event caused by CAMP-
induced increases in pCO2 (Fox et al., 2020). Second, based on magnetostratigraphic correlation of
the Westbury and Lilstock Formation with the Newark basin, the interval between the current
placement of the “precursor” CIE and the ICIE spans ~ 1.7 Ma over a 5.7 m interval (Kent et al.,
2017). Such a long time interval deposited just within a few meters requires further investigation
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of biases associated with missing time and/or high rates of time condensation within this deposit
so that the St. Audrey’s Bay section can't be used as a section with a previously recorded
“precursor“ CIE before such further analyses are conducted.
In the Tethys Ocean, the “precursor” CIE is estimated to precede the ICIE by ca.100,000
years (Ruhl and Kürschner, 2011) and by ca.110,000 years in mid-Panthalassa (Fujisaki et al.,
2020). Ruhl and Kürschner’s study proposed that late Rhaetian CAMP dike and sill intrusions into
organic-rich sediments were responsible for the “precursor” atmospheric
13
C depletion preceding
the ETE (Ruhl and Kürschner, 2011). A study of sedimentary strata underlying the main CAMP
basalts in Morocco argues that the “precursor” CIE is associated with early CAMP lava flows that
were quickly eroded after their emplacement (Dal Corso et al., 2014; Marzoli et al., 2018). Thus,
prior to the ETE, the effects of extrusive versus intrusive CAMP activity on the global carbon
cycle remain unresolved (Panfili et al., 2019).
The “precursor” carbon isotope record is not widely documented to date likely due to a
short-duration of the excursion, thus the “precursor” CIE has been captured in the rock record only
during high-resolution sampling (tens of cms or lower). For example, Yager et al. (2017)
documented a detailed carbon isotope record for every 0.5 m before and across the
Triassic/Jurassic boundary in Peru, yet the “precursor” CIE was not identified, perhaps due to
coarser sampling resolution than required for capturing the “precursor” signal. The correlation of
the PCIE is mainly based on the similar magnitude of the excursion to the ICIE and its placement,
the first negative carbon isotope excursion below the ICIE.
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References
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during the end-Triassic in the western Tethys. Palaeogeography, Palaeoclimatology,
Palaeoecology, 290(1-4), pp.151-159 (2010).
Dal Corso, J., et al. The dawn of CAMP volcanism and its bearing on the end-Triassic
carbon cycle disruption. Journal of the Geological Society, 171(2),153-164 (2014).
Fox, C.P., Cui, X., Whiteside, J.H., Olsen, P.E., Summons, R.E. and Grice, K. Molecular
and isotopic evidence reveals the end-Triassic carbon isotope excursion is not from massive
exogenous light carbon. Proceedings of the National Academy of Sciences, 117(48), pp.30171-
30178 (2020).
Fujisaki, W., Fukami, Y., Matsui, Y., Sato, T., Sawaki, Y. and Suzuki, K. Redox conditions
and nitrogen cycling during the Triassic-Jurassic transition: A new perspective from the mid-
Panthalassa: Earth-Science Reviews, v. 204, p.103173 (2020).
doi:10.1016/j.earscirev.2020.103173.
Hesselbo, S.P., Robinson, S.A., Surlyk, F. and Piasecki, S.. Terrestrial and marine
extinction at the Triassic-Jurassic boundary synchronized with major carbon-cycle perturbation:
A link to initiation of massive volcanism?. Geology, 30(3), pp.251-254 (2002).
Hesselbo, S.P., Robinson, S.A. and Surlyk, F. Sea-level change and facies development
across potential Triassic–Jurassic boundary horizons, SW Britain. Journal of the Geological
Society, 161(3), pp.365-379 (2004).
Kent, D.V., Olsen, P.E. and Muttoni, G., 2017. Astrochronostratigraphic polarity time
scale (APTS) for the Late Triassic and Early Jurassic from continental sediments and correlation
with standard marine stages. Earth-Science Reviews, 166, pp.153-180.
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Marzoli, A. et al. The Central Atlantic magmatic province (CAMP): a review. In The Late
Triassic World (pp. 91-125). Springer, Cham (2018).
Panfili, G. et al. New biostratigraphic constraints show rapid emplacement of the Central
Atlantic Magmatic Province (CAMP) during the end-Triassic mass extinction interval. Global and
planetary change, 172, 60-68 (2019).
Ruhl, M. and Kürschner, W.M. Multiple phases of carbon cycle disturbance from large
igneous province formation at the Triassic-Jurassic transition. Geology, v. 39, p. 431-434 (2011).
Ruhl, M., Hesselbo, S.P., Al-Suwaidi, A., Jenkyns, H.C., Damborenea, S.E., Manceñido,
M.O., Storm, M., Mather, T.A. and Riccardi, A.C. On the onset of Central Atlantic Magmatic
Province (CAMP) volcanism and environmental and carbon-cycle change at the Triassic–
Jurassic transition (Neuquén Basin, Argentina). Earth-Science Reviews, p.103229 (2020).
Thibodeau, A. M. et al. Mercury anomalies and the timing of biotic recovery following
the end-Triassic mass extinction. Nature Communications 7, 11147 (2016).
Yager, J.A. et al. Duration of and decoupling between carbon isotope excursions during
the end-Triassic mass extinction and Central Atlantic Magmatic Province emplacement. Earth
Planet. Sci. Lett. 473, 227-236 (2017).
Zaffani, M., Jadoul, F. and Rigo, M. A new Rhaetian δ13Corg record: carbon cycle
disturbances, volcanism, End-Triassic mass Extinction (ETE): Earth-Science Reviews, v. 178, p.
92-104 (2018).
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CHAPTER 3. UPPERMOST TRIASSIC PHOSPHORITES FROM
WILLISTON LAKE, CANADA: LINK TO FLUCTUATING EUXINIC-
ANOXIC CONDITIONS IN NORTHEASTERN PANTHALASSA BEFORE
THE END-TRIASSIC MASS EXTINCTION.
This paper was published as:
Larina, E., Bottjer, D. J., Corsetti, F. A., Zonneveld, J. P., Celestian, A. J., Bailey, J. V., 2019,
Uppermost Triassic phosphorites from Williston Lake, Canada: link to episodic euxinia in
northeastern Panthalassa: Scientific Reports, 9(1), p. 1-9.
Abstract
The end-Triassic mass extinction (ETE) is associated with a rise in CO2 due to eruptions
of the Central Atlantic Magmatic Province (CAMP), and had a particularly dramatic effect on the
Modern Fauna, so an understanding of the conditions that led to the ETE has relevance to current
rising CO2 levels. Here, we report multiple phosphorite deposits in strata that immediately precede
the ETE at Williston Lake, Canada, which allow the paleoenvironmental conditions leading up to
the mass extinction to be investigated. The predominance of phosphatic coated grains indicates
reworking in shallow water environments. Raman spectroscopy reveals that the phosphorites
contain organic carbon, and petrographic and scanning electron microscopic analyses reveal that
the phosphorites contain putative microfossils, potentially suggesting microbial involvement in a
direct or indirect way. Thus, we favor a mechanism of phosphogenesis that involves microbial
polyphosphate metabolism in which phosphatic deposits typically form at the interface of
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euxinic/anoxic and oxic conditions. When combined with data from deeper water deposits
(Kennecott Point) far to the southwest, it would appear a very broad area of northeastern
Panthalassa experienced anoxic to euxinic bottom water conditions in the direct lead up to the end-
Triassic mass extinction. Such a scenario implies expansion and shallowing of the oxygen
minimum zone across a very broad area of northeastern Panthalassa, which potentially created a
stressful environment for benthic metazoan communities. Studies of the pre-extinction interval
from different sites across the globe are required to resolve the chronology and spatial distribution
of processes that governed before the major environmental collapse that caused the ETE. Results
from this study demonstrate that fluctuating anoxic and euxinic conditions could have been
potentially responsible for reduced ecosystem stability before the onset of CAMP volcanism, at
least at the regional scale.
3.1. Introduction
The end-Triassic mass extinction (ETE) appears nearly coincident with the emplacement
of the Central Atlantic Magmatic Province (CAMP) ~201.51 million years ago (Schaller et al.,
2012; Blackburn et al., 2013; Jaraula et al., 2013; Pálfy and Kocsis, 2014; Thibodeau et al., 2016).
Approximately 80% of all marine and terrestrial species became extinct during the ETE making it
the second biggest biodiversity (Sepkoski, 1996; Alroy et al., 2010) and the third biggest ecological
crisis (McGhee et al., 2004) during the Phanerozoic. Proposed causes of the mass extinction
include CAMP-related global warming (Pálfy and Kocsis, 2014; McElwain et al., 1999;Wignall,
2001), global cooling (Guex et al., 2016), ocean acidification (Hautmann et al,. 2008; Kiessling et
al., 2007; Greene et al., 2012a, 2012b), sea-level changes (Hallam, 1981), and ocean anoxia
(Hallam, 1981; Hallam et al., 2000; Jaraula et al., 2013; Kasprak et al., 2015). The knowledge base
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of the conditions leading up to the ETE is poorly resolved, as the main focus has remained on the
timing associated with an initial emplacement of CAMP. Yet, recent studies of the pre-extinction
interval reveal biotic, climatic and geochemical changes before the onset of known CAMP
volcanism (Ruhl and Kürschner, 2011; Schoepfer et al., 2016; Davies et al., 2017; Yager et al.,
2017). Here, we present the first detailed study investigating the genesis of Upper Triassic
phosphorite deposits from Williston Lake, British Columbia, which intriguingly occur directly
before the ETE interval (Fig. 1, 2).
Phosphorite beds at Williston Lake are predominantly composed of phosphatic coated
grains. Deposits containing phosphatic coated grains are rare throughout the Phanerozoic and their
origin remains incompletely understood (Piecha, 2002; Wignall et al., 2007; Zoss et al., 2018). It
is widely accepted that direct precipitation of phosphates occurs near the sediment-water interface
and requires distinct environmental conditions (Arning et al., 2009; Crosby and Bailey, 2012; Hiatt
et al., 2015; Pufahl and Grimm, 2003). Formation of authigenic phosphorites (phosphogenesis) is
generally associated with microbial polyphosphate metabolism and biogeochemical processes
where steep or temporally dynamic redox gradient conditions occur (Arning et al., 2009; Crosby
and Bailey, 2012; Hiatt et al., 2015). Pufahl and Grimm (2003) suggested that phosphatic coated
grains are proxies for fluctuations in organic carbon flux and primary productivity. Our study
suggests that the formation of these phosphatic coated grains deposits was microbially mediated
based on textural features and Raman spectroscopy. While phosphorites are an indicator of steep
or dynamically-variable redox gradient conditions, the occurrence of benthic macrofauna within
phosphatic beds implies that transient oxygenation events occurred during phosphogenesis
(Wignall et al., 2007). Our results demonstrate a development of oxygen restricted conditions,
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which would be stressful to most benthic metazoans established in shelf waters off northeastern
Panthalassa prior to the ETE and preceding the earliest known CAMP volcanism.
3.2. Study area
Exposures of the Fernie Formation along Williston Lake, British Columbia, Canada span
the Triassic/Jurassic boundary and include the record of the entire Rhaetian Stage, the final stage
of the Triassic across different environments (Wignall et al., 2007) (Fig. 2). The siliciclastic-
carbonate strata were deposited in a foreland basin on the western side of the Pangaean continental
shelf
(Orchard et al., 2001; Zonneveld et al., 2010) (Fig. 1). The Rhaetian Stage is marked by sea-
level fall followed by a major transgression at the end of the Rhaetian coincident with an initial
worldwide negative carbon isotope excursion
(Wignall et al., 2007; Zonneveld et al., 2010) (Fig.
2).
We investigated three sections (Ne Parle Pas Point, Pardonet Creek, and Black Bear Ridge)
that contain phosphorite deposits in the interval immediately preceding the ETE. The sea-level fall
during the Rhaetian generated a major hiatus in the more proximal Black Bear Ridge section such
that nearly the entire Rhaetian sequence is missing at this locality; nevertheless, a veneer of
phosphatic coated grains is preserved at the sequence boundary. Strata recording a more complete
Rhaetian Stage are at the distal sites of Ne Parle Pas Point and Pardonet Creek where both sites
record lowstand strata missing at the Black Bear Ridge locality (Fig. 2). The upper 13 m of the
Ne Parle Pas section and the upper 3.5 m of the Pardonet Creek sequence consist of calcareous
siltstone interbedded with phosphatic grainstone beds recording a transition from offshore to lower
shoreface depositional environments (Fig. 2). In general, phosphorite accumulations are associated
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with a condensed, transgressive record
(Pufahl and Groat, 2017), yet intriguingly Williston Lake
phosphorites are deposited within the regressive sequence
(Wignall et al., 2007) (Fig. 2).
3.3. Results
3.3.1. Description of phosphorite deposits
The phosphorite beds studied here represent high-energy phosphatic grainstone beds that
vary from 5 to 40 cm in thickness (Fig. 2). The grainstone beds represent storm events sandwiched
between calcareous siltstone to sandstone deposits. Phosphatic clasts were transported from a
shallower part of the shelf to the deeper offshore transition zone during high-energy, storm-related
events as evidenced by fragmented grains, rip-ups, phosphate grapestones and scouring surfaces
between fine-grained siltstone and coarse-grained phosphatic grainstone beds (Fig. 3A-B, E-F).
The phosphorite deposits predominantly consist of phosphatic coated grains with some peloids,
muscovite, quartz silt, bioclasts and phosphatic pebbles embedded in a sparry calcite matrix.
According to Wignall et al. (2007), the phosphatic units contain some of the more biotically diverse
assemblages versus surrounding units, and include infaunal and epifaunal bivalves, nautiloids,
ammonoids, and echinoderms. In all localities, phosphatic coated grains vary in shape from
spheroids to ellipsoids and are predominantly fragmented due to reworking and winnowing (Fig.
3A). Occasionally phosphatic coated grains embedded in a phosphatic matrix are present (Fig.
3B). Phosphatic coated grains are 50 to 380 µm in diameter, more commonly between 100 and
150 µm. Phosphatic cortices are uniformly composed of Ca-phosphate (apatite) while nuclei
composition include sedimentary clasts (most common), quartz, feldspar, and shell fragments. The
nuclei of phosphatic coated grains are coated by concentric phosphatic laminae, which vary in
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thickness and alternate between light brown and dark brown layers (Fig. 3 C, D). Concentric layers
are irregular in places replicating the shape of the nucleus and occasional objects within laminae
(Fig. 3C, D). The presence of concentric and irregular laminations along with unaltered bioclasts
suggest the primary origin of phosphatic coated grains excluding the possibility of diagenetic
replacement.
Samples dissolved in acetic acid from the Ne Parle Pas site that contain nuclei composed
of calcium carbonate intraclasts reveal phosphatized tubes (Fig. 4C). Phosphatized tubes are
between 2 and 3 microns in diameter creating an interwoven network identical in shape, size, and
structure to endolithic borings (Tribollet and Payri, 2001). Thus, these carbonate intraclasts were
infested by euendoliths during “normal” conditions followed by rapid phosphatization before
micritization could occur.
3.3.2. Microbial mineralization
Raman spectroscopy is widely used as an analytical tool for differentiation between
carbonaceous material of biogenic versus abiogenic origin in the rock record. At all Williston Lake
localities, micro Raman spectroscopy documents intense and broad bands occurring at around
1350 cm
-1
(D band) and 1600 cm
-1
(G band) within phosphatic cortices which are diagnostic of
organic matter (kerogen)
(Marshall et al., 2010) (Fig. 5A). Further analysis of the deconvoluted
carbon first-order spectrum derived from the D-G spectrum seen in Fig 5A shows five bands
resolved into Gaussian bands where the high difference between bands D and D4 can be observed
(Fig. 5A). The second derivative spectra of the D and G bands illustrate that the G band doesn’t
have a doublet on the negative peak (Fig. 5B). Both differences in D4 and D bands and the absence
of a doublet on the negative peak of the G band corroborate the presence of disordered
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carbonaceous matter, likely of biological origin, within the phosphorites
(Marshall et al., 2010). In
contrast, Raman spectroscopic analysis conducted on the matrix and nuclei of phosphatic coated
grains does not record features that support the presence of any kind of carbonaceous material
(Fig. C, D).
SEM and petrographic examinations of studied samples show microscopic spherical
cavities (0.5 to 1 μm in diameter) within phosphatic coated grains cortices (Fig. 4A-B, D).
Photomicrographs of these cavities reveal a distinct rim and hollow core structure that rules out
the possibility of abiotic precipitates that resemble microbial forms
(Mänd et al., 2010). Cosmidis
et al.
36
documented coccus-like and rod-like biomorphs in a Miocene/Pliocene Peruvian
phosphatic crust that are identical in shape, size and distribution to our microscopic spherical
objects. Salama et al.
37
showed that microspheres (0.5 to 2.5 μm in diameter) embedded in
carbonaceous matrix from Upper Cretaceous phosphatic peloids are fossilized remains of
coccoidal bacteria. Both studies concluded that the observed microspheres were once a part of
microbial colonies that formed near the oxic-anoxic boundary in zones of sulfate reduction
(Cosmidis et al., 2013; Salama et al., 2015). Thin section observations revealed the presence of
curved filamentous structures, ~1 μm in width and varying in length from 5 to 27 μm (Fig. 4D),
which we interpret as putative microbial remains. Observed microscopical spherical cavities and
filamentous morphotypes within carbonaceous material indicate the bacterial origin of relatively
diverse microbial communities.
The evidence for microbial mineralization is unsurprising as all of the currently accepted
mechanisms of marine phosphogenesis require microbes to concentrate P either in a direct or an
indirect way (Cosmidis et al., 2013). We would like to emphasize that the presence of microbes
within the cortices of phosphatic coated grains do not necessarily imply their direct role in the
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apatite accretion within phosphatic coated grains, although such a scenario is plausible, but rather
that they may have played a fundamental role in the delivery of P via polyphosphate metabolism.
Documented pyrite framboids within phosphoclasts imply the presence of sulfide likely provided
by sulfate reducing bacteria in reducing conditions
(Vietti et al., 2015) (Fig. 4E-F). This is in
accordance with the study by Wignall et al. (2007) which documented euxinic conditions based
on framboidal size at Williston Lake sections.
3.4. Discussion
Modern and ancient phosphorite deposits are mainly associated with oceanic upwelling
regions associated with hypoxic oxygen-minimum zones (OMZ) overlying organic-rich sediments
(e.g., Crosby and Bailey, 2012; Hiatt et al., 2015). In such regions, phosphogenesis is thought to
be driven by microbes that concentrate P as part of polyphosphate metabolism (Crosby and Bailey,
2012; Hiatt et al., 2015; Vietti et al., 2015), with the colorless sulfur bacteria, in addition to others,
commonly considered key players. The sulfur bacteria live at interfaces between organic rich,
sulfidic conditions below and oxic conditions above, and are thought to accumulate polyphosphate
in order to help survive during prolonged, but fluctuating anoxic and sulfidic conditions (Mänd et
al., 2010). Thus, many sedimentary phosphate concentrations indicate that environmental
conditions cycled between oxic and euxinic/anoxic during phosphogenesis.
Mechanisms of authigenic apatite precipitation that do not involve polyphosphate
metabolism include the sourcing of P from vertebrate bone
(Suess, 1981), or from dissolving Fe-
oxide-bearing mineral phases, again under stratified redox conditions (Crosby and Bailey, 2012;
Ruttenberg and Berner, 1993). While these P sources are plausible drivers of Williston Lake
phosphogenesis, we do not favor them as explanations. In the former case, fish bones are not
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abundant in the Williston Lake deposits and they do not serve as nuclei for the phosphatic coated
grains. Similarly, with respect to P being concentrated through adsorption and subsequent
dissolution of iron hydroxides, we would expect this mechanism to operate in a system dominated
by iron-rich siliciclastic deposition, as opposed to the organic-rich system here that contains pyrite
(Fig. 4E-F), indicating a sulfide-dominated depositional environment such as those that favor
phosphogensis via concentration through microbial polyphosphate metabolism (Goldhammer et
al., 2010; Schulz and Schulz, 2005).
Here, we consider the presence of phosphatic coated grains to indicate conditions
fluctuated between oxic and sulfidic conditions in shallow water as a result of intensified oceanic
upwelling and OMZ expansion in the lead up to the ETE in northeastern Panthalassa. The presence
of phosphorites suggests that the foreland basin was well-connected to the ocean at the time of
phosphogenesis. Models investigating genesis of phosphatic coated grains from Arning et al.
(2009) and Pufahl and Grimm
(2003) propose that phosphatic coated grains are deposited near the
sediment-water interface (upper 5-20 cm of sediment) in organic-rich sediment under suboxic to
anoxic conditions where repeated reworking of phosphatic grains and fluctuation of redox
conditions play a crucial role. Although phosphatic coated grains are sometimes referred to as
phospho-ooids, the process responsible for phospho-ooid formation is different from carbonate
ooids, which precipitate by wave agitation in supersaturated waters with calcium carbonate
(Salama et al., 2015), while the apatite in phosphatic coated grains precipitates authigenically
below the sediment-water interface
(Pufahl and Grimm,
2003). We suggest that these phosphatic
coated grains formed between storm and fair-weather wave-base, but specifically in proximity to
the wave-agitation zone where they were more prone to episodic reworking and mixing by storms
and where the upwelling front would be best developed and intensified
(Pufahl and Groat, 2017).
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High-energy storm events reworked phosphate clasts further transporting them to the current place
of deposition (phosphatic grainstone beds). The infilling of microbial borings in carbonate clasts
by phosphate indicates relatively rapid phosphatization, before the borings were infilled by
cements, or the microbial borers could fully micritize the carbonate grains (Fig. 4C).
The presence of putative microbial fossils within the phosphate cortices lends credence to
a microbial involvement either in an indirect way by concentrating high amounts of P or in a direct
way by facilitating an actual apatite accretion. The fact that the phosphatic beds contain
macrofauna suggests a strong association with transient oxic conditions during which benthic
metazoa colonized the seafloor until the next euxinic/anoxic event
(Wignall et al., 2007). Taken
together, the presence of phosphorites indicates a dynamic environment that shifted between oxic,
hypoxic and possibly anoxic or euxinic conditions in the time preceding the ETE. Our study
demonstrates evidence supporting microbial mineralization during the phosphogenesis either in a
direct or an indirect way, likely by polyphosphate-metabolizing bacteria, similar to those that
mediate phosphogenesis in modern settings that fluctuate between oxic and euxininc/anoxic
conditions (Zoss et al., 2018; Vietti et al., 2015).
Schoepfer et al.
(2016) and Kasprak et al.
(2015) investigated an open ocean, deep-water
section (~200-500 m water depth) from northeastern Panthalassa, spanning the Triassic-Jurassic
boundary several hundred km to the west of Williston Lake, at Kennecott Point, British Columbia
(Fig. 1). Both of these studies interpret nitrogen-limited conditions, water-column stratification
and deoxygenation at Kennecott Point through an ~10 m-thick interval, estimated to represent
approximately half a million years
(Schoepfer et al., 2016) before the ETE using geochemical and
biomarker proxies. Although precise geochronology is problematic at Williston Lake, the timing
of biogeochemical disturbance at Kennecott Point coincides well with deposition of the upper
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Rhaetian phosphate grainstone beds. Given that the Kennecott Point (deep) and Williston Lake
(relatively shallow) sites are likely contemporaneous, it would appear that a broad area of
northeastern Panthalassa experienced fluctuating euxinic-anoxic conditions in the lead up to the
ETE, beginning ~500 kyr before the extinction. Fluctuating, oxygen-restricted conditions likely
created a hostile environment for benthic fauna at least in shallow water settings where most
benthos are less adapted to low oxygen conditions. For example, off the coast of Oregon, recent
intensified upwelling brought oxygen-poor waters to shallow shelf depths (<50 m) where emergent
anoxia nearly eradicated the macroscopic benthic invertebrate community and initiated the
development of sulfide-oxidizing bacterial mats
(Chan et al., 2008). At Williston Lake sites,
Wignall et al.
(2007) documented the demise of shallow-water infaunal bivalves right before the
initial negative carbon isotope excursion marking the major environmental collapse of the ETE.
This stressed environment potentially made marine biota more susceptible to subsequent cascading
effects from CAMP emplacement, at least in northeastern Panthalassa.
Photic zone euxinia combined with anoxic conditions is considered to be a potent
mechanism for the ETE since these conditions are widely documented in Panthalassic and Tethys
basins during the ETE (Jaraula et al., 2013; Kasprak et al., 2015). It is worth noting that the first
appearance of euxinia on the shelves, as suggested by the presence of upper Rhaetian phosphorites,
could indeed precede the onset of CAMP volcanism, adding to the growing dataset that
environmental conditions began to deteriorate before the beginning of CAMP volcanism in
different parts of the globe (Ruhl and Kürschner, 2011; Schoepfer et al., 2016; Yager et al., 2017).
Dike and sill intrusions in organic rich sediments in Brazil were proposed as a potential mechanism
that drove the climate change preceding the onset of CAMP volcanism (Ruhl and Kürschner, 2011;
Davies et al., 2017; Cleveland et al., 2008). Study
(Cleveland et al., 2008) using pedogenic
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carbonate isotopes as a proxy for temperature variations has documented two periods of extreme
temperature increase by 6°C in congruence with atmospheric CO2 rise preceding the ETE. Thus,
it is worth considering that intensified oceanic upwelling and OMZ expansion in northeastern
Panthalassa was possibly related to climate warming as a result of higher pCO2. Additional studies
are required to reveal conditions leading up the ETE which governed on the regional versus global
scale.
3.5. Conclusions
Spectroscopic, petrographic and SEM investigations on the genesis of uppermost Triassic
phosphorites from Williston Lake, British Columbia, provide evidence supporting microbially-
induced mineralization, likely by polyphosphate-accumulating bacteria. The genesis of phosphatic
coated grains requires deposition near the sediment-water interface under suboxic to anoxic
conditions where repeated reworking of phosphatic grains and fluctuation of redox conditions play
an essential role (Arning et al., 2009; Pufahl and Grimm, 2003). Our study provides direct
biosedimentary evidence that fluctuating euxinic-anoxic conditions existed in relatively shallow
marine settings (above storm-wave base) preceding the ETE in northeastern Panthalassa. These
results are compatible with previous studies of Schoepfter et al.
(2016) and Kasprak et al. (2015)
from the deep-water Kennecott Point section, suggesting that environmental disturbances, likely
episodic euxinia, preceded the ETE for approximately 500 kyr. For the first time, our study shows
that euxinic-anoxic conditions existed not just in the deeper part of the northeastern Panthalassic
basin prior to the ETE, but also in shallow water settings of the foreland basin covering a very
broad area of northeastern Panthalassa. Intervals of phosphogenesis are linked to periods of an
intensified oceanic upwelling and OMZ expansion where possibly sulfide-oxidizing microbial
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communities were thriving inducing apatite precipitation, while the benthic biota flourished in
between euxinic/anoxic intervals, at least at the Williston Lake region. Such conditions were likely
stressful for shallow water benthic metazoans making them more susceptible to cascading effects
from CAMP volcanism. Additional studies from Panthalassic and Tethys basins are required to
further elucidate conditions leading up to the ETE at the regional and global scale and their effects
on ecosystems.
3.6. Methods
Specimens from different phosphatic horizons covering all three studied sections were
examined. Standard petrographic microscopy was performed on thin sections using a Zeiss Axio
Imager.M2m equipped with a Zeiss HRc camera. Internal grain structure and elemental
composition were investigated on a FEI Nova NanoSEM 450 in back-scattered electron mode with
the help of an Energy-dispersive X-ray spectroscopy microprobe. To determine mineral content
and the presence of kerogen, we used a Horiba XploRa PLUS Raman Microscope and Horiba
XGT-7200 X-ray fluorescence microscope. Samples were dissolved in 10% acetic solution for 72
hours in order to observe the morphology of phosphatic clasts.
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Figures
Figure 1. Paleogeography and modern location of study localities. A) Lower Jurassic
paleogeographic reconstruction
(Greene et al., 2012a) with the approximate paleolocation of
Williston Lake sites after Greene et al. (2012b)
and Kennecott Point site after Kasprak et al. (2015)
B) Map of the studied localities at Williston Lake, British Columbia modified from Wignall et al.
(2007) 1 = Black Bear Ridge (56.08758333° N, 123.04388889 ° W), 2 = Pardonet Creek
(56.03527778 ° N, 123.03500000° W), 3 = Ne Parle Pas (56.01682778 ° N, 123.08305556° W).
CAMP extent
Pangaea
Tethys
Panthalassa
5 km
Williston Lake
thrust fault
Triassic strata
3
2
1
B
Williston Lake
A
Kennecott Point
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Figure 2. Stratigraphic columns of studied sections showing depositional environment. Green
arrows show the position of studied samples depicted in the figures below. Placement of Initial
Carbon Isotope Excursion is after Wignall et al.
(2007). Volcano marks the end-Triassic mass
extinction. Aragonite fans described in Greene et al.
(2012b) Pr. Fm = Pardonet Formation.
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500 µm
150µm
C
A
B
500 µm
D
500 µm
E
F
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Figure 3. Photomicrographs of phosphatic coated grains (PCG). All images are in plane-
polarized light.
A) Fragmented phosphatic coated grains. Note size and shape variation. Sample PC 10.
B) Phosphatic coated grains embedded within phosphatic crust resembling grapestone structure
with phosphatic peloids. Sample NPP17.5.
C) Light and dark brown concentric laminations. White arrow points to the divergence area
where outer lamina replicate shape of a clast within cortex. Red arrow points to unaltered shell
fragment within the cortex of phosphatic coated grain. Sample PC 7.
D) Phosphatic coated grain with irregular concentric laminations. Sample NPP 17.5.
E) Coarser grained P-rich sediment separated by scouring surface from underlying finer-grained
sediment. Sample NPP 16.
F) Bivalve clasts filled with silt and peloids that were ripped up and transported by storms. PC7
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F
10 µm
B
2 µm
C
30 µm
10 µm
D
10 µm
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Figure 4. Photomicrographs and SEM images of putative microbial structures, euendolith borings,
and pyrite framboids.
A) SEM image of microscopic spherical cavities (~0.5 – 1 µm in diameter) within PCG cortex.
Sample BBR0.
B) Close-up of image A. Sample BBR0.
C) SEM image of sample dissolved in acetic acid, which reveals phosphatized euendolith borings
(dashed line). Sample NPP 17.5.
D) Photomicrograph in plane-polarized light of filamentous structure (black arrows) within
phosphate and microscopical spherical cavities with distinct rim (red arrows) resembling microbial
remains. Sample PC 7.
E) SEM image of sample dissolved in acetic acid, which reveals an aggregation of pyrite
framboids. Sample NPP 17.5.
F) Backscatter SEM image of pyrite framboids within phosphate. Sample PC 7.
Figure 5. Raman spectroscopic analysis.
A) Representative Raman spectrum of phosphate cortex showing high intensity peaks of D-G
bands and deconvolution of D and G bands modeled by six Gaussian peaks below (fitted peaks
A
0 500 1000 1500
−10
−5
0
5
10
Raman Shift (cm
-1
)
Intensity
second derivative
second dervative smoothed
B
D
C
E
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are scaled for clarity). High intensity peaks of D-G bands and big difference between bands D4
and D verify the biogenic origin of carbonaceous matter
34
. Sample PC7.
B) The second derivative spectra derived from the first order carbon spectra (Fig. 5A) shows no
negative doublet on the negative peak at the G band (see red arrow) corroborating the presence
of biogenic carbonaceous material within phosphate cortices. Sample PC7.
C) Representative Raman spectrum of calcareous matrix showing low intensity peaks of D-G
bands and deconvolution of D and G bands modeled by three Gaussian peaks below (fitted peaks
are scaled for clarity). CC = calcite. Sample PC7.
D) The second derivative spectra derived from the first order carbon spectra (Fig. 5C) shows
absence of any intensity within D-G bands corroborating the absence of biogenic carbonaceous
material within calcareous matrix. Sample PC7.
E) Representative Raman spectrum of nuclei of PCG showing low intensity peaks of D-G bands.
QTZ = quartz. Sample PC7.
CHAPTER 4. MICROFACIES AND MACROFAUNAL ANALYSIS OF
UPPER RHAETIAN EIBERG MEMBER SEQUENCES FROM THE
NORTHERN CALCAREOUS ALPS
ABSTRACT
The late Rhaetian time-interval is a critical period for the study of paleoenvironmental and
paleoecological changes leading up to the end-Triassic mass extinction. The Northern Calcareous
Alps (NCA) in Austria preserve one of the most complete marine sedimentary records of upper
Rhaetian strata in the world. We conducted a detailed microfacies and macrofaunal study of five
key sections spanning the upper Rhaetian (upper Kössen Formation, Eiberg Member) in the NCA.
Four of the studied sites (Kuhjoch, Eiberg, Juifen, and Schlossengraben) were deposited across the
intraplatform Eiberg Basin with the fifth site (Restentalgraben) deposited on the terrigenous-
influenced northern side of a small carbonate platform (“Oberrhaet Limestones), near the
northwestern margin of the Eiberg Basin. This study documents the presence of an ecologically
diverse and trophically complex marine ecosystem at the Restentalgraben locality within the
shallow water platform “Oberrhaet Limestone”. In the basin center, deeper water environments
are characterized by a less complex trophic marine ecosystem, mainly dominated by bivalves and
brachiopods, but still ecologically diverse and robust benthic marine community right before the
extinction. Based on the documented microfacies and macrofaunal analyses in the Tethys realm,
we propose that the combination of reduced salinity, episodic suboxic conditions and ocean
acidification cause the abrupt ecological crisis during which the eurytopic opportunistic
paleocommunities flourished followed by their demise during the main phase of the extinction as
environmental conditions worsened due to main phase of CAMP volcanic activity. When
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extinction patterns are compared between Panthalassic and Tethys basins, the Tethys experienced
the sudden tempo of ecological changes in contrast to the more protracted nature of ecological
shifts recorded in the Panthalassa.
4.1. Introduction
The Northern Calcareous Alps (NCA) preserve one of the most complete marine
sedimentary records of upper Rhaetian strata in the world with the Global Stratotype Section and
Point (GSSP) for the Triassic/Jurassic boundary located at Kuhjoch pass, Tyrol, Austria
(Hillebrandt et al., 2013). Triassic/Jurassic outcrops in the NCA are extensively studied with a
well-developed ammonite and conodont biostratigraphy, as well as palynological,
sedimentological and geochemical data (e.g., Hillebrandt et al., 2007; Lindstrom et al., 2019;
Richoz et al., 2015; Tomasowych et al., 2006a; Rizzi et al., 2020; McRoberts et al., 2012; Mette
et al., 2016, 2019; Ruhl et al., 2009, 2011). Although outcrops in Austria have been extensively
studied, the main focus has remained on the end-Triassic mass extinction (ETE) interval. Yet, the
conditions leading up to the extinction event are more complex than currently thought (e.g., Larina
et al., 2019, 2021; Rigo et al., 2020; Kasprak et al., 2015; Davies et al., 2015; Ruhl et al., 2009)
highlighting the need for more studies investigating environmental and paleoecological trends
leading up to the ETE event. Most studies that generated pre-extinction data cover sections
deposited across the Panthalassa Ocean (e.g., Yager et al., 2017; Fujisaki et al., 2018, 2020;
Kasprak et al., 2015; Larina et al., 2019, 2021). However, studies from both Panthalassic and
Tethys basins are required for reconstruction of temporal and spatial processes operating before
the ETE on a global scale.
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This study aims to construct an integrated high-resolution framework encompassing
published and new data from the geochemical, stratigraphic, sedimentological, and faunal record
for the upper Rhaetian in the Northern Calcareous Alps, Austria. This established framework will
facilitate deciphering of environmental conditions and ecological structure in the Eiberg Basin
leading up to the ETE and will be a useful tool for correlation of strata on a regional and local
scale.
4.2 Geological Setting
During the Late Triassic, the strata of the NCA were deposited on a 300-km-wide shelf
situated on the northwestern margin of the Neotethys Ocean in the subtropical climatic belt,
situated about 30° north of the equator (Fig. 1) (Haas et al., 1995; Reinhold and Kaufmann, 2009).
A tropical climate and low sea level facilitated the deposition of large lagoons and carbonate
intraplatforms (Golebiowski, 1989; Tomasowych, 2006a; Ruhl et al., 2009; Richoz and Kyrstyn,
2015; Galbrun et al., 2020; Rizzi et al., 2020).
The Eiberg Basin was an extensive, carbonate intraplatform basin bordered by land and a
partly terrigenous-influenced carbonate platform called the “Oberrhaet Limestone” in the north-
west (Fig. 1C). In the south-east it was bordered by the carbonate Dachstein platform that was
connected to the open water of the Hallstatt basin and was proposed as a potential gateway for the
Eiberg basin with the Neotethys ocean (e.g., Korte et al., 2017) (Fig. 1). Two other basins, the
Csövár Basin and the Slovenian Trough, situated in the oceanward external margin of the
Dachstein platform, started to form in the Carnian and as a result differed from the Eiberg Basin
(Fig. 1B) (Rizzi et al., 2020). The Eiberg Basin encompasses various shallow water lithofacies
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including large lagoon and occasional patch reefs and fringing reefs (Schäfer, 1979; Kuerschner
et al., 2007).
In the studied sections, the Rhaetian Stage is represented by the mixed siliciclastic-
carbonate lithologies of the Kössen Formation. As shown by multiple studies, the Kössen
Formation consists of large-scale shallowing-upward sequences superimposed on small-scale
fluctuations (Golebiowski 1990, 1991; Holstein, 2004; Tomasowych 2006a, Rizzi et al., 2020).
Two main paleoenvironmental models are proposed for deposition of the Eiberg Basin: (1) the
depositional sequences in the basin were controlled by relative sea-level changes (Golebiowski,
1991) and (2) the depositional sequences were controlled by climatic variations reflecting changes
in nutrients, turbidity and siliciclastic supply to the basin interiors (Tomasowych, 2006). Which
model prevailed during deposition of the Eiberg Basin is still unclear as evidence exists in favor
of both scenarios (Golebiowski 1990, 1991; Holstein, 2004; Tomasowych, 2006; Rizzi et al.,
2020).
The Kössen Formation is subdivided into the Hochalm Member (middle Rhaetian) and the
Eiberg Member (upper Rhaetian) (Fig. 2; Fig. 3). The Hochalm Member is characterized by a
bivalve dominated shallow water environment with shallowing-upward transgressive/regressive
sequences (Golebiowski, 1990, 1991). The Eiberg Member is characterized by a brachiopod
dominated deeper water environment with a predominantly deepening trend interrupted by
secondary shallowing upward events (Golebiowski, 1990, 1991; Mette et al., 2016). During the
deposition of the Eiberg Member, the Eiberg Basin continuously subsided reaching water depths
at ~150-300 m leading to a deeper neritic environment below storm wave base (Tomasowych,
2006a, 2006b; Mette et al. 2012, 2016; Korte et al., 2017). The Eiberg Member consists of four
units (Fig. 3). Units 1 and 4 consist of bioclastic limestones with abundant echinoderm detritus.
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Units 2 and 3 consist of intercalated marls, marlstones and mudstones (e.g., Golebiowski 1989,
1990; Tomasowych, 2006a, 2006b).
The uppermost Rhaetian records distinct lithological facies change from basinal carbonates
of the Eiberg Member (Kössen Formation) to more clayey and marly-rich deposits of the
Tiefengraben Member (Kendlbach Formation). This transition coincides with a sea-level fall and
the onset of the ETE (e.g., Ruhl et al., 2010; McRoberts et al., 2012; Hillebrandt et al., 2013;
Richoz et al., 2015) (Fig. 2). The basin center was minimally affected by the sea level fall recording
continuous sedimentation, meanwhile marginal shallow water environments underwent long-
lasting emersion developing an erosional unconformity on the top of the carbonate platform (Fig.
2) (e.g., Hillebrandt et al., 2013; McRoberts et al., 2012; Richoz and Kyrstyn, 2015). Most recent
studies propose that the unconformity is rather related to submarine erosion associated with
acidification and a calcification crisis related to the end-Triassic mass extinction resulting in the
demise of the Dachstein carbonate platform (Gawlick et al. 1999, 2009; Pálfy et al., 2021).
The very top of the Eiberg Member is distinguished by a distinct, dark colored, platy, up
to 20-cm-thick bed referred to as the T-bed (Fig. 4) (e.g., Kürschner et al., 2007; Hillebrandt and
Krystyn, 2009; Hillebrandt et al., 2013). The top of the T-bed is marked by a resistant, black,
bituminous and mostly laminated layer that contains phosphatic fish remains (scales) and pyrite
nodules (Fig. 4). Hillebrandt et al. (2013) assign the bituminous top of the T-bed to the beginning
of a regression phase and consider it as a continuation of the uppermost Eiberg Member based on
the faunal and lithological uniformity of the bed. McRoberts et al. (2012) restrict the T-bed only
to the top 3-5 cm of the T-bed (bituminous part) and characterize it as a condensed horizon of the
early transgressive system tract assigning it to the base of the Tiefengraben Member. In here, we
adapt the interpretation of the T-bed used by Hillebrandt et al. (2013). Regardless of the
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interpretation on how it was deposited, this distinctive bed records the negative initial carbon
isotope excursion (ICIE) found worldwide and the last occurrence of the last Triassic ammonoid
Choristoceras marshi marking the onset of the ETE in the NCA (e.g., Ruhl et al., 2009; Bonis et
al., 2010; Korte et al., 2019). Distinct REE (rare earth element), Ir, Hg patterns and clay
mineralogical composition of the topmost part of the T-bed was interpreted as evidence of mafic
volcanic ash fallout derived from CAMP volcanism (Pálfy and Zajson, 2012; Percival et al., 2017).
Increased values in Total Organic Carbon (TOC) up to 14% (Ruhl et al., 2009), laminated
sediments, and the presence of pyrite nodules at the top of the T-bed are suggestive of reduced
mixing and oxygen-depleted water bottom conditions during its deposition in the end-Triassic
Eiberg Basin (Bonis et al., 2010, Hillebrandt et al., 2013). Also, this interval coincides with a
drastic increase of conifer (Cheirolepidiaceae) pollen and terrestrial palynomorph concentrations
followed by a peak of green algae (Cymatiosphaera), inferring an influx of terrestrial organic
matter due to increased seasonality and erosion of the hinterland that resulted in reduced salinity
of surface waters and an acme of green algae leading to stratification of the water column (Bonis
et al., 2010).
The lowermost part of the Tiefengraben Member is a 0.2-1m thick gray, brown to yellow
marl called locally the Grenzmergel (Fig. 5A) (Hillebrandt et al, 2013). The Grenzmergel interval
marks the disappearance of Triassic ammonoids and conodonts but still yields Triassic micro- and
nannofossils (Kürschner et al., 2007; Hillebramdt et al,. 2013) as well as numerous episodic low
diversity eurytopic opportunistic bivalve assemblages (McRoberts et al., 2012). The Grenzmergel
interval is overlain by reddish oxidized, clayey marls known as the Schattwald beds that vary in
thickness from 2 m (at Kuhjoch) to 8 m (at Restentalgraben) (Fig. 5). The Schattwald beds mark
the peak extinction phase as this interval is barren of macrofauna and culminates a regressive cycle
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(Hillebrandt et al., 2013). However, McRoberts et al. (2012) suggests that the entire Tiefengraben
Member was deposited solely within the transgressive cycle. The Schattwald beds are overlain by
gray argillaceous marls of the upper part of the Tiefengraben Member (Fig. 5B). The occurrence
of the first Jurassic ammonoid Psiloceras spelae tirolicum marks the Triassic-Jurassic boundary
at the GSSP Kuhjoch site at 3.2 m above the Schattwald beds.
4.3 Material and Methods
Samples collected during this study are restricted to the Eiberg and Tiefengraben Member.
We investigated five stratigraphic sections across the Eiberg Basin in the Northern Calcareous
Alps of Austria: Eiberg, Schlossgraben, Juifen, Kuhjoch and Restentalgraben (Fig. 6). The
stratigraphic sections were described and measured prior to faunal and sedimentary sampling at
all localities, except at Eiberg. At the Eiberg section, data were collected following bed assignment
and stratigraphic measurements of Golebiowski (1989) and Mette et al. (2016).
4.3.1. Macrofaunal analysis.
A total of 43 bulk samples (9-11 L) were collected at intervals of interest at the
Restentalgraben, Juifen and Eiberg sections. Each bulk sample was disintegrated manually into
rock fragments of ~1 cm
3
. Faunal specimens were identified to the most precise taxonomic level
possible. Taxonomic identifications were based on Pearson (1968; 1977), Golebiowski (1989),
Siblík (1998), Hautmann (2001; 2006) and Michalík et al. (2013). In addition to bulk samples
some beds were extensively sampled in the field in order to maximize sample size. In this case,
the mechanical disintegration of each bed was timed assuring that the total volume of rock
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processed at each horizon exceeded 10 L. Barren samples and unidentified specimens were
excluded from the analysis, resulting in 303 identifiable individuals belonging to 45 taxa. This
dataset is mainly composed of bivalves, brachiopods and ammonoids. The number of bivalve and
brachiopod individuals for a given species were estimated based on the number of articulated shells
and the dominating number of either dorsal or ventral valves (Gillinski and Bennington, 1994).
Ammonoids were quite rare and in most cases unfragmented. Paleoecological traits such as tiering,
feeding mode and degree of motility were assigned to fossil specimens following Bambach (1983)
and Bush et al. (2007).
4.3.2. Microfacies analysis.
A total of 94 thin sections have been examined with a Zeiss Axio Imager.M2m polarized-
light microscope equipped with a Zeiss HRc camera. The description of the microfacies followed
the classification established by Flügel and Munnecke (2010) and Golebiowski (1989) (Table 1).
Thin-sections have been assessed for the presence/absence of biological elements and
compositional analysis.
4.3.3. Data analysis.
Two-way cluster analysis.
Two-way cluster analysis is a highly informative approach allowing evaluation of clusters
of samples and taxa plotted at right angles to one another where the resulting data matrix depicts
the abundance of each taxon within each sample (Patzkowsky and Holland, 2012). Thus, this
method allows one to recognize which suites of taxa are similar as well as which taxa cause the
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samples to cluster. Two-way cluster analysis was performed using the R package ‘cluster’ version
2.2.1 (Maechler et al., 2021) and the R package ‘sparcl’ version 1.0.4 (Witten and Tibshirani,
2018). The R package ‘pheatmap’ version 1.0.12 (Kolde, 2019) was used to combine the R-mode
and Q-mode cluster analysis in order to produce a two-way cluster analysis.
Q-mode cluster analysis was performed on the species-abundance matrix in order to define
relationships in faunal similarity among samples while R-mode cluster analysis was performed on
the species-abundance matrix in order to identify which taxa co-occur. In order to account for
variation in sample size, the species-abundance matrix was transformed into a proportional
abundance of a species relative to the total number of specimens during Q and R-mode cluster
analyses. The Bray-Curtis distance matrix and Ward’s method for the most compact linkage
(McCune and Grace, 2002) were used during both Q-mode and R-mode cluster analyses. The R-
mode and Q-mode cluster analyses were combined in order to create a two-way cluster analysis
that allows one to determine the biofacies for clusters of samples.
Ordination Analysis
Non-metric (or non-parametric) multidimensional scaling (NMDS) is an ordination
technique that is widely used in ecological studies of modern and past environments. NMDS
allows the analysis of ecological as well as environmental datasets (McCune and Grace, 2002).
NMDS of the culled species-abundance matrix was performed to identify lithofacies correlated
with faunal assemblage variations. NMDS was performed using the R package ‘vegan’ version 2.5
–7 (Oksanen et al., 2020). The AltGower distance metric was used based on the best stress values,
the goodness of fit between original distance matrix and the reduced distance matrix of the
ordination (McCune and Grace, 2002).
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Turnover Rates
Total turnover, relative appearances and disappearances of species between depositional
sequences and system tracts, were calculated using the R package ‘codyn’ version 2.0.4 (Hallett
et al., 2020). The codyn package calculates species turnover between time bins as summed gained
and lost species relative to total species richness across both time periods. This approach closely
resembles the Jaccard dissimilarity method. In fact, species turnover rates were calculated using
Jaccard dissimilarity as well and returned the same results as total turnover rates in the ‘codyn’
package. In addition to total turnover, the ‘codyn’ package allows calculation of the number of
species that appeared or disappeared in the second time period relative to total species richness in
both time periods (Hallett et al., 2020). Turnover metrics between the T-bed and intervals below
were calculated using collected data from this study combined with the faunal assemblages
reported by McRoberts et al. (2012) for the T-bed.
At the Restentalgraben section, samples were assigned to a position within each binning
system: T-bed, parasequences and depositional sequences. At the Restentalgraben site,
depositional sequences cannot be defined with certainty since 7 m in the lower part of the section
are not exposed in addition to limited data on sedimentological features, so depositional sequences
are assumed based on the correlation of Unit 4 and 3 with the Eiberg section. Grouping of
parasequences as time bins for turnover metric is based on sample size equaling to 5 or more
species in order to maximize sample resolution. At the Eiberg section, samples were assigned to a
position within each binning system: the T-bed and depositional sequences. A stratigraphic
sequence interpretation was adapted from Mette et al. (2016; Fig. 9) where authors based their
interpretation using gamma-ray and sedimentological data.
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4.4. Description of localities.
4.4.1 Kuhjoch, GSSP locality (47º29’02”N, 11º31’50”E).
Kuhjoch is the Global Stratotype Sections and Point locality for the base of the Jurassic
System situated at Kuhjoch Pass, Karwendel Mountains, Tyrol, Austria.
Lithology. – The southern flank of the Karwendel Syncline exposes the sedimentary
sequence of the upper Rhaetian Kössen Formation, which is overlain by the uppermost
Rhaetian/lowermost Hettangian Kendlbach Formation (Fig. 7-8). The studied section consists of a
6.05 m thick interval of the upper Eiberg Member (Unit 4) of the Kössen Formation conformably
overlain by the 7 m thick Tiefengraben Member of the Kendlbach Formation (Fig. 7). The
uppermost 4 m of the Kössen Formation consists of thick-bedded bioturbated bioclastic
wackestone intercalated with occasional thin-bedded calcareous marls (3-6 cm) (Fig. 8B). The
lowermost part of the Kössen Formation is mainly composed of thinly laminated yellow marls
underlain by fissile black shale containing pyrite nodules (Fig. 8E). The uppermost 20 cm of the
Kössen Formation is the so-called T-bed characterized by dark color, higher clay content and platy
weathering (Fig. 8D). It is overlain by a 2 cm thick laminated bituminous layer containing fish
scales and a high abundance but low diversity bivalve assemblage (McRoberts et al., 2012). Only
samples for microfacies analysis were collected at the Kuhjoch locality. Bulk sediments for
macrofaunal analysis were not collected at this site.
The base of the Tiefengraben Member (Kendlbach Formation) is composed of ~30 cm
thick yellowish partly laminated marls, the Grenzmergel interval. Hillebrandt et al. (2013) report
up to 13 cm thick gray to brownish clay-rich marls containing pyrite concretions and worm-shaped
traces at the very base of the Tiefengraben Member. The base of the Tiefengraben Member is
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overlain by ~2 m thick reddish oxidized, clayey marls known as the Schattwald beds (Fig. 5B; Fig.
8F). The Schattwald beds are topped by 5 m of thick gray to brownish marls (Fig. 5B). The
Triassic-Jurassic boundary is situated 5.8 m above the Eiberg Member (Kössen Formation) and
marked by the “Golden Spike” at the site (Fig. 5B). The transition from the Upper Triassic into
the Lower Jurassic sediments is exposed partially on the East and partially on the West side of the
Kuhjoch section. For detailed lithostratigraphic description of Kuhjoch East and Kuhjoch West
exposures see Hillebrandt et al. (2013).
Macrofauna. – The upper Eiberg Member is characterized by low ammonite diversity and
abundance (Hillebrandt et al., 2013). The last occurrence of the last Triassic ammonoid
Choristoceras marshi is recorded at the top of the T-bed marking the demise of Triassic
ammonoids and the onset of the ETE. The first occurrence of the first Jurassic ammonoid
Psiloceras spelae tirolicum is documented at the 5.8 m level marking the Triassic-Jurassic
boundary (Hillebrandt et al., 2013) (Fig. 7).
Typical Triassic bivalves such as Cassianella sp. and Lyriochlamys valoniensis are present
below the T-bed within the upper Eiberg Member (McRoberts et al., 2012). Agerchlamys textoria
and rare Pseudolimea cf. hettangiensis are present within the bituminous layer of the T-bed with
Cardinia hybrida right above the T-bed (McRoberts et al., 2012; Hillebrandt et al., 2013).
Agerchlamys textoria, Pseudolimea cf. hettangiensis and Cardinia hybrida represent an
opportunistic bivalve assemblage taking over during the initial extinction peak (Fig. 7B)
(McRoberts et al., 2012). A spiriferid brachiopod Oxycolpella oxycolpos is present within the
upper Eiberg Member including the T-bed. The occurrence of rhynchonellids is documented in the
lower part of the Schattwald beds (Hillebrandt et al., 2013). The presence of echinoderm fragments
is detected in thin-sections across the Eiberg Member and in one sample right below the Triassic-
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Jurassic boundary. Crinoid ossicles and fragments of echinoids were reported above the
Schattwald beds and up the section by Hillebrandt et al. (2013).
Microfossils. – The upper Eiberg Member carbonates contain foraminifers such as small
sized Trochammina, Ammodiscus, and polymorphinids while the base of the T-bed contains a
diverse fauna of Nodosariidae with few Textulariina (Hillebrandt et al., 2013). The diversity of
foraminifers drops towards the top of the T-bed (Hillebrandt and Kment, 2011). A finely
agglutinated siliceous foraminifer Hippocrepina is a dominant species across the Schattwald Beds
indicating ecologically unfavourable conditions for calcitic fauna during the deposition of this
interval (Clemence et al., 2010; McRoberts et al., 2012). Sixty percent of the Rhaetian ostracod
species became extinct within the T-bed and didn’t recover until the Lower Jurassic (Hillebrandt
et al., 2013).
During thin-section analysis, this study identified Nodosariid Lagenid foraminifers within
Unit 4 including bed 16-17, 20 and 22 with Pseudonodosaria sp. within bed 18. Other Nodosariid
Lagenids such as Lenticulina sp. were identified within bed 19, 23, 25 and 27 and Austrocolomia?
within bed 21.
Geochemistry. – Detailed organic carbon isotope analysis for Kuhjoch and other NCA
sections has been documented by Ruhl et al. (2009) and Hillebrandt et al. (2013). Ruhl et al. (2009)
reported a negative shift of 6‰ in d
13
Corg values coinciding with an increase by 8% in TOC at the
top of the T-bed (Fig. 7C). This excursion is defined as the negative initial carbon isotope excursion
(ICIE). The d
13
Corg values shift towards positive values at the base of the Tiefengraben Member
followed by another negative shift of 2‰ at the top of the Schattwald beds marking the main
negative carbon isotope excursion (MCIE) (Ruhl et al., 2009) (Fig. 7C). The first excursion in
Hg/TOC ratio is observed at the top of the T-bed coinciding with the ICIE (Percival et al., 2017).
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Multiple peaks in Hg/TOC are recorded within the lower four meters of the Tiefengraben Member
signifying pulsatory intensity of CAMP volcanism (Percival et al., 2017) (Fig. 7D). The strontium
isotopes
87
Sr/
86
Sr record shows a slight radiogenic increase within the lower three meters of the
Kössen Formation from 0.70775 to 0.70780 (Kovacs et al., 2020).
4.4.2 Schlossgraben (47º28’32”N, 11º28’54”E).
Lithology. – The Schlossgraben sequence is deposited within the western Eiberg Basin in
the Karwendel syncline (Hillebrandt et al., 2008). The studied section consists of a 2.28 m thick
upper Eiberg Member (Unit 4) interval of the Kössen Formation conformably overlain by a 1.5 m
thick interval of the Tiefengraben Member of the Kendlbach Formation (Fig. 9). The Eiberg
Member consists of thick-bedded bioclastic wackestone to packstone intercalated with occasional
thin-bedded calcareous marls (2 - 6 cm) topped by a 17 cm thick T-bed (Fig. 9, 10). The upper 3
cm of the T-bed is a dark brown bituminous layer. Only samples for microfacies analysis were
collected at the Schlossgraben locality. Bulk sediments for macrofaunal analysis were not
collected at this site.
The base of the Tiefengraben Member or the Grenzmergel Bed is composed of a 48 cm
thick yellowish marl with a lense of pyrite at the base (Pic. 5A; Fig. 10D). The Grenzmergel bed
is overlain by the 1 m thick Schattwald beds, and the top of the Shattwald beds is covered.
Macrofauna. – Choristoceras marshi is identified at the top of the Eiberg Member.
McRoberts et al. (2012) documented an opportunistic bivalve assemblage of Agerchlamys textoria,
Pseudolimea cf. hettangiensis, Cardinia hybrida and Melangrinella sp. at the top of the T-bed and
the basal part of the Tiefengraben Member (Fig. 9B).
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Microfossils. – During thin-section analysis, this study identified Nodosariid Lagenid
foraminifers such as Astacolus sp., within beds 3 and 6 of Unit 4.
Geochemistry. – The negative initial carbon isotope excursion of 4‰ and an increase by
8% in TOC are recorded at the top of the T-bed (Ruhl et al., 2009) (Fig. 9C).
4.4.3 Juifen (47º32’53”N, 11º37’32”E).
Lithology. – The Juifen sequence is deposited within the western Eiberg Basin in the
Karwendel syncline, 10 km in a direct line North East of the Kuhjoch site (Fig. 1; Fig. 6). The
Juifen site is interpreted as having been deposited slighlty deeper in the basin than Kuhjoch, based
on features of Jurassic sediments (Brandner et al., 2011). The Juifen locality lacks index fossils for
assigning units of the Eiberg Member. We propose that our studied section spans Unit 4 of the
Eiberg Member based on continuous sedimentation (lack of hiatuses and hardgrounds), bed
thickness, macrofossils, stratigraphy and proximity to the Kuhjoch section. The Juifen section
consists of a 10.12 m thick unit of intercalated thick-bedded bioclastic to marly wackestones and
packstones with a few grainstone beds within the basal part of the section (Fig. 11). The uppermost
part of the section comprises a 13 cm thick T-bed (Fig. 11-12). The upper 3 cm of the T-bed is
comprised of a dark grey bituminous layer containing a typical opportunistic bivalve assemblage
(Fig. 12). The interval between two and four meters is covered by vegetation likely due to the
fine-grained nature of the sediments.
Macrofauna. – For the first time, this study documents a macrofaunal invertebrate
assemblage at the Juifen section that is described below. The last Triassic ammonoid
Choristoceras marshi (Fig. 12D) is found within the bituminous layer along with Cardinia hybrida
(Fig. 12G), Chlamys valoniensis, Chlamys sp., Melangrinella sp. (Fig. 12E) and Palaeocardita sp.
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The T-bed right below the bituminous layer contains Agerchlamys textoria, Melangrinella sp. and
Pseudolimea cf. hettangiensis. The upper Eiberg Member below the T-bed contains bivalves such
as Atreta intusstriata, Cassianella inaequiradiata and Inoperna schafhaeutli with the brachiopod
Rhynchonella subrimosa. Crinoid ossicles and fragments of echinoids were documented across the
entire section during microfacies analysis. Brander et al. (2011) reported a high abundance of
sponge spicules.
4.4.4 Eiberg (47°33’00”N, 12°10’07”E).
Lithology. – The Eiberg section is situated in an active cement quarry “SPZ Zementwerk
Eiberg GmbH” (Fig. 14B). The Eiberg sequence was deposited in the central part of the Eiberg
Basin (Golebiowski, 1991) (Fig. 1C). The Eiberg section spans the upper part of the Hochalm
Member (top of Unit 2 to Unit 4) and the entire Eiberg Member, separated from the lower Jurassic
sediments of Allgäu Formation by a prominent fault. The studied section is 69 m thick and covers
the entire Eiberg Member including the T-bed (Fig. 13). The measurements and sample ID beds
at the Eiberg Section were mainly based on the stratigraphic log published by Mette et al. (2016,
Fig. 9) combined with the lithostratigraphic description from Golebiowski (1989). The studied
section consists of alternating bioclastic and micritic limestones intercalating with marls and shales
(Fig. 14A). The Eiberg Basin underwent a general upward deepening trend during the deposition
of Unit 1 to 3 of the Eiberg Member reaching maximum water depth at the base of Unit 3
(Golebiowski, 1989, 1990, 1991; Richoz and Krystyn, 2015; Mette et al., 2016). The lower part of
Unit 3 is characterized by intercalated black shales and thin-bedded mudstones (Richoz and
Krystyn, 2015). Besides an apparent lithofacies change, the deepening of the basin is supported by
disappearance of shallow water ostracods (Urlichs, 1972; Mette et al., 2012, 2016) and terebratulid
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brachiopods as well as dominance of the basinal bivalve Oxytoma inaequvalve and appearance of
spiriferid brachiopods (Golebiowski, 1989; 1991; Mette et al., 2016). Such change in bio- and
lithofacies could be attributed to deoxygenation of bottom waters (Mette et al., 2012)
Unit 4 of the Eiberg Member is characterized by thick-bedded limestones with occasional
marls (Fig. 14A). Unit 4 represents a gradual regressive phase evidenced by thicker carbonate beds
(Fig. 14A,C), and downslope-transported, shallow water bivalves Palaeocardita and brachiopods
Oxycolpella and Fissirhynchia (Golebiowski, 1989; Richoz and Krystyn, 2015; Mette et al., 2016).
The uppermost part of the studied section comprises a 20 cm thick T-bed with a 4 cm thick
bituminous layer at the very top. Zoophycos and Chondrites trace fossils are common across the
section (Richoz and Krystyn, 2015).
Macrofauna. – Unit 1 of the Eiberg Member spans an ammonoid Zone Vandaites
stuerzenbaumi followed by the ammonoid Zone Choristoceras marshi (Unit 2 to Unit 4). The
lower part of Unit 2 is characterized by an ammonoid Subzone Choristoceras ammonitiforme
(Golebiowski, 1991; Mette et al., 2012) (Fig. 15). Golebiowski (1989; 1991) provided a detailed
study of brachiopod faunal distribution in the Eiberg Basin. Units 1 to 3 are characterized by the
Fissirhynchia Biofacies where Fissirhynchia fissicostata is a dominant species (up to 60%) with
less dominant Rhaetina pyriformis, Zeilleria norica, Austrirhynchia cornigera, Zugmayerella
koessenensis and Oxycolpella oxycolpos. Unit 4 is characterized by the Oxycolpella Biofacies
which is dominated by Oxycolpella oxycolpos (up to 70%) with less dominant Fissirhynchia
fissicostata (20-30%), Zeilleria norica and Sinucosta emrichi (Siblik, 2008; Golebiowski 1991).
This study documented the bivalves Cassianella inaequiradiata, Chlamys favrii, Chlamys
sp., Entolium sp., Homomya sp., Inoperna (Triasoperna) schafhaeutli (Fig.15E), Isocyprina cf.
ewaldi, Isocyprina sp., Oxytoma inequivalvis, Placunopsis alpina, Protocardia rhaetica, and
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Schafhaeutlia sp., the brachiopods F. fissicostata, and R. pyriformis and the ammonoid C.
ammonitiforme within Unit 2 of the Eiberg Member at the Eiberg section. Within Unit 3, we
documented the bivalves Chlamys sp., Inoperna (Triasoperna) schafhaeutli, Oxytoma
inequivalvis, brachiopods F. fissicostata (Fig.15C), Rhynchonella subrimosa, Zeilleria elliptica
(Fig.15D), Zugmayerella koessenensis, the ammonoid C. marshi and an unknown gastropod
specimen (Fig. 13C). Only two horizons were sampled within Unit 4: the top of the T-bed
(bituminous layer) and ~10 cm below the T-bed. Right below the T-bed, we identified the bivalves
Cardinia hybrida, Grammatodon sp., Nuculana claviformis, Pecten sp., Pseudolimea cf.
hettangiensis (Fig.15A), and the ammonoid Choristoceras sp. (Fig. 13C). The top of the T-bed is
characterized by a bivalve assemblage comprising Agerchlamys textoria, Cardinia hybrida,
Chlamys sp., Melangrinella sp. and significantly dominated by Pseudolimea cf. hettangiensis (Fig.
13C; 15A).
Microfossils. – Mette et al. (2012) documented ostracod assemblages across the Eiberg
section. The lower Unit 2 of the Eiberg Member contains the first occurrence of the ostracods
Triceratina fortenodosa and Ogmoconcha aff. hagenowi along with Lobobairdia triassica and
Nodobairdia alpine (Mette et al., 2012). The rare occurrence of Nodobairdia alpine within Unit 2
is suggestive of transportation from shallow environments by storm events. The upper part of Unit
2 is represented by monotypic assemblages of Ogmoconcha sp. 1 along with high abundance of
the involutinid foraminifera Trocholina cf. verrucose (Mette et al., 2012). Deepening of the basin
within Unit 3 overlaps with distinct changes in foraminiferal and ostracod assemblages (for more
details see Mette et al., 2012) corroborating an increase in water depth and a depleted oxygen
conditions. During thin-section analysis, this study identified Variostoma coniforme within Bed
D1 and undetermined duostominidae foraminifera within bed M.
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Geochemistry. – A positive oxygen isotope shift by ~0.5‰ is recorded from the bottom of
the section up to the lower part of Unit 3 of the Eiberg Member signifying bottom water cooling
by ~2.5 °C (Fig. 14B) (Mette et al., 2012; Korte et al., 2017). The bottom water cooling is attributed
to the deepening of the basin (Mette et al., 2012). The negative carbon isotope excursion of ~1.5‰
in the lower part of Unit 3 is decoupled from the oxygen isotope values and overlaps with an
increase in amounts of phytoclasts and spore/pollen ratios (Holstein, 2004) which is indicative of
increased humidity during this time interval (Mette et al., 2012). The negative initial carbon isotope
excursion of 4‰ and an increase by 8% in TOC are recorded at the top of the T-bed at the Eiberg
section (Ruhl et al., 2009).
4.4.5 Restentalgraben (47°50’27”N, 14°32’21”E)
Lithology. – The Restentalgraben sequence was deposited on the northern side of a
terrigenous-influenced small carbonate platform called “Oberrhaet Limestone” (Fig. 1; Fig. 6)
(Ruhl et al., 2009; McRoberts et al., 2012). The Restentalgraben locality lacks index fossils for
assigning units of the Eiberg Member. We propose that our studied section spans Unit 4 and Unit
3. We place a tentative boundary between Unit 4 and 3 at ~12 m based on shallowing upward
cycles, bed thickness and a change from siliciclastic to carbonate-dominated facies as observed in
sections at the Eiberg Basin (Fig. 13D; Fig. 16D).
The studied section is a 27.5 m thick succession characterized by alternating carbonate and
siliciclastic-dominated facies (Fig. 16A). The lower 2.5 meters represent the shallowest part of the
section. It consists of thick-bedded hard bioturbated grainstone beds intercalated with dark grey
marls (between 12 to 30 cm thick) and occasional mudstone beds. The top three grainstone beds
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are very resistant with wavy surfaces resembling hardground horizons. Grainstone beds consist of
abundant ooids, crinoidal ossicles, bivalves, and gastropods and occasional brachiopod shell
fragments. The interval between -25.5 and -12 m is dominated by siliciclastic-dominated facies
(thick marls) suggesting an increase in water depth and/or increase in humidity corresponding to
Unit 3 of the Eiberg Member as documented at the Eiberg locality. The horizon between -20 and
-14 m is covered likely due to the fine-grained nature of the sediments. The tentative Unit 4 above
12 m is characterized by shallowing upward sequences of thick-bedded limestone beds alternating
with marl deposits. The uppermost part of the studied section is overlain by an ~7 cm thick T-bed
characterized by dark color, higher clay content, laminations and the presence of pyrite nodules
(Fig. 4A,B).
Macrofauna. – This study documented a macrofaunal invertebrate assemblage described
below. The lower part of the section contains the bivalves Chlamys sp., Nuculana sp., Placunopsis
alpina, and Rhaetavicula concorta. The upper part of the section contains Atreta intusstriata,
Chlamys sp., Isopryna sp., Modiolus sp., Myophoriopis? isoceles, Nuculana claviformis, Nuculana
sp., Palaeonuculana sundaica, Palaeonuculana sp., “Permophorus” elongatus, Placunopsis
alpina, Pinna sp., Protocardia rhaetica, Protocardia sp., Pseudocorbula ewaldi, Pteromya sp.,
Rhaetavicula concorta, Rhaetavicula sp., Schafhaeutlia sp. and unknown gastropod remains. The
T-bed contains bivalves Chlamys sp., Myophoriopis? isoceles, Palaeonuculana sp., Placunopsis
sp.?, Rhaetavicula sp., and Schafhaeutlia sp.. McRoberts et al. (2012) documented a eurytopic
opportunistic bivalve assemblage containing abundant Cardinia hybrida, Melangrinella sp., and
Agerchlamys textoria at the top of the T-bed. Although brachiopods were not identified during
bulk processing, rare brachiopod bioclasts are documented in thin sections.
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Microfossils. – This study documented benthic agglutinated Glomospira sp., involutinid
foraminifer Triosina sp. (Fig. 22H), and hyaline (Nodosariids) foraminiferas.
Geochemistry. – A negative initial carbon isotope excursion of 3.5‰ and an increase by
~7% in TOC are recorded at the top of the T-bed at the Restentalgraben section (Ruhl et al., 2009).
4.5 Results
4.5.1 Microfacies Types.
MF1--Mudstone (Dunham) (Figure 19)
This microfacies type is homogenous in structure and often is bioturbated. Occasional
samples show laminations. Sparite veins are common (Fig. 19A). The bioturbated mudstone
consists of the micritic matrix with very fine peloids and occasional bioclasts of echinoderms,
foraminifers, ostracods, brachiopods, and bivalves (Fig. 19). The MF1 facies type corresponds to
mud facies D3 in Golebiowski (1989) and to SMF1 in Flügel and Munnecke (2010). Depositional
setting is common in basin (FZ1), open sea shelf (FZ 2), and outer ramp (Flügel and Munnecke,
2010).
MF2 - Silty mudstone/marls (Dunham) (Figure 20)
Fine calcarenite-calcisiltite laminae alternate with fine quartz silt (20B). Some samples are
homogeneous in structure and composition. This microfacies type is mostly devoid of bioclasts
with some exceptions. Goethite framboids and quartz silt are common features. MF2 mainly occurs
within the extinction interval. All thin sections across the extinction interval exhibit distinguishing
features such as matrix saturated with a reddish golden hue and often with silvery blotches (Fig.
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20E-F). MF2 corresponds to SMF1 in Flügel and Munnecke (2010) influenced by terrigenous
input. Depositional setting is common in deep water basin (FZ1), open sea shelf (FZ 2), and outer
ramp (Flügel and Munnecke, 2010). The inference of depositional setting of samples that are
restricted to the extinction interval is complicated by disappearance of calcareous organisms due
to ocean acidification and oxygen-depleted conditions.
MF3 - Bioclastic wacke- to packstone (Figure 21)
This microfacies type is characterized by bioturbated bioclastic wacke- to packstone with
a matrix mainly composed of micrite and microsparite. Rare samples show laminations and contain
silt. Sparitic ghost structures of bioclasts (Fig. 21A), as well as sparite veins and stylolites (Fig. A,
H) are common features. The bioclasts are mainly composed of echinoderms, brachiopods and
bivalves with less abundant ostracods, foraminifers, gastropods and ammonoid remains. Shell
material is highly fragmented, angular and varies in size. The MF3 facies type corresponds to the
mud facies transition between D1 and D2 in Golebiowski (1989) and to SMF1/SMF1-Burrowed
in Flügel and Munnecke (2010). Depositional setting is common in basin (FZ1), open sea shelf
(FZ 2), and outer ramp (Flügel and Munnecke, 2010).
MF4 - Bioclastic pack- to rudstone (Figure 22)
This microfacies type is characterized by poorly sorted pack- to rudstones with a matrix
mainly composed of fine-grained micrite and microsparite. The MF4 type only occurs at the
Restentalgraben section. The bioclasts are dominated by bivalve and echinoderm fragments.
Benthic agglutinated Glomospira sp., the involutinid foraminifer Triosina sp. (Fig. 22H), and
hyaline (Nodosariids) foraminifera are documented within MF 4. Bioclasts of gastropods,
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brachiopods, foraminifers, ammonoids, corals, and bryozoans are present with occasional mud
clasts and quartz silt (Fig. 22B-C). Shells are mainly recrystallized with sparite calcite cement.
Valves of bivalves and brachiopods are disarticulated but in most cases whole (Fig. 22). Some
samples show the parallel arrangement of shells pointing to some current control (Fig. 22G)
(Flügel and Munnecke, 2010) (Fig. 22G). The MF4 facies type corresponds to Lumachellen facies
L7a in Golebiowski (1989) that is interpreted as a proximal tempestite facies deposited in a
strongly agitated, aerated, shallow subtidal environment. The MF4 facies type corresponds to SMF
5 in Flügel and Munnecke (2010). Occurence of this facies is common in reef-flank facies, slope,
adjacent to reefs and deposited in forereef position and reef slopes, or in backreef settings and in
lagoons (Flügel and Munnecke, 2010).
MF5 - Coated bioclastic grainstone (Figure 23)
This microfacies type is present in two samples (RS45 and RS53) at the Restentalgraben
section (Fig. 23). These two samples represent coated grainstone microfacies MF5, but differ in
terms of diagenetic imprint since RS45 is characterized as a hardground. Therefore, a separate
description for these two samples will be provided below. Sample RS45 is characterized by
strongly micritized coated grains embedded in sparry cement. Grains are mainly rounded partially
phosphatized intraclasts composed of bioclasts, ooids and mud clasts (Fig. 23A-D). Skeletal grains
are primarily replaced with sparry cement. Bioclastic grains include coral, foraminifera, sponge
spicules, and echinoderm, as well as gastropod and bivalve shells (Fig. 23A-D). Sample RS53 is
characterized by micritized coated grains embedded in sparry and partially micritic cement with
quartz silt (Fig. 23E-F). Grains are primarily rounded and in some cases phosphatized. Grains
include bioclasts of bivalves, gastropods, brachiopods, foraminifers and echinoderms with ooids.
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Most skeletal clasts are replaced with sparry cement. Stylolites are observed (Fig. 23E). The MF5
facies type corresponds to Lumachellen facies L3 in Golebiowski (1989) that occurred at the
margin of carbonate sand bars within a high-energy environment. The MF5 facies type
corresponds to SMF 11 in Flügel and Munnecke (2010). Occurence of this type of microfacies is
commom in winnowed edge platform sand and in reefs.
4.5.2 Faunal Data
Eiberg Basin. – The faunal composition of deeper water-facies deposited in the Eiberg
Basin (Juifen and Eiberg sections) consists of 23 species/19 genera of bivalves, 8 species/6 genera
of brachiopods and 2 species/1 genus of ammonoids. Additionally, thin section analysis revealed
the presence of abundant echinoderm fragments, occasional ostracods, and rare gastropods and
foraminifera (Fig. 24-25). Seven categories of life mode are detected in the Eiberg Basin with the
most abundant mode of life represented by stationary suspension feeding epifauna (Fig. 25). The
epifaunal stationary suspension feeding mode of life is mainly represented by a relatively high
abundance of rhynchonellata brachiopods and pectinid bivalves.
The lower part of the Eiberg Member (Unit 2) has the highest diversity and abundance
across the section. The only exception is the top of the T-bed which is skewed by the high
abundance of a single taxon, Pseudolima cf. hettangiensis (Fig. 13, 25). Four modes of invertebrate
life characterize Unit 2 where an epifaunal stationary suspension feeding mode of life is the most
common followed by epifaunal facultatively mobile suspension feeding, nektonic actively mobile
carnivore and infaunal facultatively mobile suspension/deposit feeding, respectively (Fig. 25). The
lower part of Unit 3 is the deepest part of the section characterized by suboxic conditions (Mette
et al., 2012). Consequently, it is characterized by the lowest richness solely dominated by
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rhynchonellata brachiopods and choristoceratid ammonoids which correspond to epifaunal
stationary suspension feeding and nektonic actively mobile carnivore modes of life (Fig. 25). As
the Eiberg section shallows up the Kössen Formation, the diversity of facies elements increases
along with the modes of life (Fig. 25). The macrofaunal bulk sample analysis of Unit 4 at the
Eiberg section was performed only at the very top of the Kössen Formation within the bituminous
layer (top of the T-bed) and 10 cm below the T-bed or 30 cm below the bituminous layer. At the
Juifen section, the macrofaunal bulk sample analysis was accomplished across Unit 4 but was
limited to 12 identifiable specimens, not taking into account the T-bed. The low number of
invertebrate specimens at the Juifen section is likely an artifact of the taphonomic bias associated
with carbonate facies (Darroch, 2012; Kidwell et al., 2012) where recrystallization and hardness
of limestones affect the preservation potential and extractability of macrofauna. For example,
brachiopod specimens are observed in cross-sections of beds at the outcrop but could be rarely
extracted as whole specimens suitable for precise taxonomic identification (Fig. 12C).
Nevertheless, shell macrofaunal components in bulk samples show agreement with macrofaunal
fragments in thin sections with the exception of echinoderm fragments that are harder to identify
in hand samples. Microfossil components such as ostracods and foraminifera were identified
primarily in thin sections.
The documented macrofaunal assemblage of the T-bed from this study correlates well with
the eurytopic opportunistic paleocommunity reported by McRoberts et al. (2012). The T-bed
macrofaunal composition across Eiberg, Juifen, Schlossgraben and Kuhjoch sections overlaps but
differs in species richness. The highest diversity of species within the T-bed was documented at
the Juifen section where 7 bivalve species and 1 choristoceratid ammonoid were identified. Using
the published record of the T-bed macrofaunal composition from McRoberts et al. (2012), the
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lowest richness (2 bivalve species) of the T-bed is documented at the Kuhjoch section in
comparison to other studied sections deposited in the Eiberg Basin. The T-bed is dominated by
epifaunal stationary and facultatively mobile suspension feeding bivalves (Fig. 24-25). The only
exception is the presence of a single specimen of Palaeocardita sp. at the top of the T-bed at the
Juifen section, which is characterized by an infaunal facultatively mobile suspension feeding mode
of life. This singleton likely represents an outlier as it was not documented anywhere else in the
basin. Therefore, Palaeocardita sp. will not be included in further discussion of the T-bed. At the
Eiberg section, an interval 30 cm below the T-bed contains a diverse macrofaunal assemblage,
although less abundant, in terms of species richness and mode of life compared to the T-bed above.
This horizon, 30 cm below the bituminous layer, is characterized by 5 bivalve species and 1
choristoceratid ammonoid, with 5 modes of life compared to 5 bivalve species within the top of
the T-bed represented solely by stationary suspension feeding epifauna. Both Cardinia hybrida
and Pseudolima cf. hettangiensis are documented 10 cm below and at the top of the T-bed.
However, the abundance of Pseudolima cf. hettangiensis drastically increases from 1 to 90
specimens up the section. The single mode of life and a sudden increase in abundance of
Pseudolima cf. hettangiensis illustrate the rapid change in environmental conditions within the
short period of time and the rise of the opportunistic bivalve assemblage in the early stages of the
extinction event.
“Oberrhaet Limestone”. – The macrofaunal composition of shallower water-facies at the
Restentalgraben section deposited on the northern side of the “Oberrhaet Limestone” carbonate
platform consists of 16 species of bivalves as identified during macrofaunal bulk sample analysis
(Fig. 1C; Fig. 16). In petrographic thin-sections, shell fragments of abundant bivalves,
echinoderms, corals, occasional brachiopods, gastropods, foraminifers, rare bryozoans and
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ammonoids were identified (Fig. 22, 23, 26). Six categories of life mode were detected at
Restentalgraben which vary across the section (Fig. 26).
The lower three meters of the Restentalgraben section represent the shallowest lithofacies
as evidenced by the deposition of coated bioclastic grainstone beds solely restricted to the bottom
of the section (Fig. 26). The bulk macrofaunal assemblage is limited to two species/two singletons
that we do not consider as a representative bivalve assemblage due to low sample count. Yet, it
records two modes of life, epifaunal facultatively mobile and stationary suspension feeding. On
the other hand, microfacies analysis reveals a more accurate depiction of diverse carbonate
components including fragments of brachiopods, gastropods, corals, echinoderms and
foraminifers. The RS42 marl bed, deposited right above the grainstone beds, consists of low
diversity but high abundance of tiny bivalves (<0.8 mm). Nuculana sp. and Rhaetavicula concorta
have been identified within the RS42 bed corresponding to infaunal facultatively mobile
suspension feeding and epifaunal stationary suspension feeding modes of life respectively (Fig.
26). Thin section analysis of the RS39 rudstone with fine-grained packstone bed shows diverse
calcareous constituents of bivalves, brachiopods, gastropods, corals, echinoderms, bryozoans,
ammonoids and foraminifers (Fig. 16, 26).
Unit 4 contains the most diverse and abundant macrofaunal invertebrate assemblage across
the section spanning all six modes of life. The lower part of Unit 4 is dominated by ostreids, the
bivalve Rhaetavicula concorta and the pectinid bivalve Placunopsis alpina (Fig. 16, 26). Four
modes of life were identified within the lower Unit 4 where the epifaunal stationary suspension
feeding mode of life is most common followed by infaunal facultatively mobile suspension/deposit
feeding, epifaunal facultatively mobile suspension feeding and infaunal facultatively mobile
suspension feeding bivalves (Fig. 26). In thin sections, calcareous components are identical to the
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diverse assemblage documented down the section within the RS39 bed. The upper part of Unit 4
is dominated by pectinid bivalves such as Placunopsis alpina and Chlamys sp. (Fig. 16, 26). In
addition to the four modes of life described above, the fifth mode of life appears for the first time
characterized by an infaunal facultatively mobile chemosymbiotic category represented by the
bivalve Schafhaeutlia sp. (Fig. 16, 26). The macrofaunal bivalve assemblage of this T-bed differs
from T-beds documented in sections deposited outside the Eiberg basin. The T-bed at
Restentalgraben is represented by relatively even abundance of the bivalves Chlamys sp.,
Myophoriopis? isoceles, Palaeonuculana sp., Placunopsis sp.?, Rhaetavicula sp., and
Schafhaeutlia sp. and it spans the same five modes of life as documented within the upper Unit 4
(Fig. 16, 26).
4.5.3 Species turnover.
At the Eiberg section, the lower four time bins correlate to depositional sequences and the
uppermost bin spans the T-bed (Table 2; Fig. 27). The lowest turnover rates of 75% are
documented between bin one, two and three spanning Unit 1, 2 and the lower part of Unit 3 (Fig.
27; Table 2). In the lower part of the section, a turnover rate of 75% is generated by loss of species
while the turnover rate right above it is generated by species gain signaling the appearance of a
new fauna. The largest turnover of 87% took place between Unit 3 and Unit 4 dictated by an almost
even appearance and disappearance of species. The turnover rate between the T-bed and the
uppermost depositional sequence is 82% where 55% is accounted for by the gain of new species
within the T-bed (Table 2).
At the Restentalgraben section, species turnover is compared between stacking
parasequences and presumed depositional sequences (Table 2; Fig. 28). When compared between
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parasequences, the lowest turnover of 66% occurred between Unit 3 and the lower part of Unit 4
and the highest turnover of 86% took place between the T-bed and the upper part of Unit 4 (Fig.
28; Table 2). The highest turnover is driven by species appearance of 62%. When compared
between depositional sequences, the lowest turnover of 72% is between the lower and upper part
of the section and the highest turnover of 82% took place between the T-bed and the upper
depositional sequence (Unit 4). The highest turnover rate is driven by the 64% appearance of new
species within the T-bed compared to the interval below (Fig. 28; Table 2).
4.5.4 Two-way cluster analysis.
In two-way cluster analysis performed at the sample level and based on faunal abundances,
3 main clusters have been recognized for the Q-mode and for the R-mode (Fig. 29).
In the Q-mode, Cluster 1A contains samples from all three sections spanning all lithofacies
except for the grainstone. Faunal composition is dominated by diverse bivalves such as Chlamys
sp., Placunopsis alpina, and Rhaetavicula concorta. Cluster 1B is restricted to the Juifen and
Eiberg sections where three lithofacies are present including marl, mudstone and wackestone.
Cluster 1B is dominated by the rhynchonellid brachiopod Rhynchonella subrimosa. Cluster 2
contains samples exclusively from the Eiberg section predominantly from mudstone and marl
lithofacies with faunal composition dominated by the rhynchonellid brachiopod Fissirhynchia
fissicostata, and the choristoceratid ammonoid Choristoceras sp. Other diverse brachiopods are
present within cluster 2 including Zeilleria eliptica, Zugmayerella koessenensis, Oxycolpella
oxycolpos and Rhaetina sp. Cluster 3 contains samples from the Eiberg and Restentalgraben
sections from diverse lithofacies. Taxonomic composition of cluster 3 is dominated by the bivalve
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Chlamys sp. followed by the choristoceratid ammonoids Choristoceras sp., as well as diverse
bivalves, and two rhynchonellid brachiopods Fissirhynchia fissicostata and Rhaetina sp. (Fig. 29).
In the R-mode, cluster 1 contains species restricted to a semi-infaunal and infaunal tiering
structure with a suspension and deposit feeding mode of life. Cluster 1 is characterized by a faunal
assemblage containing the bivalves Nuculana claviformis, Palaeonuculana sundaica,
Pseudocorbula ewaldi, Pteromya sp., Modiolus sp., and Protocardia rhaetica. Cluster 2 represents
the faunal assemblage documented in the T-bed. Cluster 2B contains a eurytopic opportunistic
bivalve assemblage as described by McRoberts et al. (2012) including Pseudolima cf.
hettangiensis, Cardinia hybrida, Agerchlamys textoria, and Meleagrinella sp. whereas cluster 2A
contains samples restricted to the Juifen section. Cluster 3A contains species dominated by an
epifaunal tiering structure with a suspension feeding mode of life including a diverse assemblage
of brachiopods, bivalves and co-occurring choristoceratid ammonoids. Cluster 3B is characterized
by a diverse assemblage of bivalves primarily appearing at the Restentalgraben section.
4.5.5 Ordination analysis.
The Nonmetric Multidimensional Scaling (NMDS) ordination plots lithofacies such that
samples close to one another are similar in macrofaunal composition (Fig. 30). The-T-bed has been
distinguished as its own lithofacies due to its unique sedimentology, macrofaunal assemblage and
extinction significance. The T-bed macrofaunal samples are closely plotted together with a slight
overlap from all three sections (Fig. 30A). With the exception of the T-bed, the rest of the lithofacies
are widely dispersed. Assemblage compositions from the Juifen and Eiberg sections show clear
overlap, while Restentalgraben just partially overlaps with the Eiberg section (Fig. 30B). The
differentiation between the shallower Restentalgraben and deeper Eiberg locality is likely related to
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the difference in depositional settings. The overlap could be driven by the transport of shallow water
fauna into the deeper part of the Eiberg basin via turbidity currents.
4.6 Discussion
4.6.1 Facies interpretation
Microfacies type MF 1 was recognized at the Restentalgraben, Eiberg, Schlossgraben and
Kuhjoch sections. The mudstones (MF 1) deposited at the Eiberg, Schlossgraben and Kuhjoch
sections reflect autochtonous sediments deposited under low-energy condition with slow
sedimentation in a deeper basinal environment in the intraplatform Eiberg Basin (Flügel and
Munnecke, 2010). The presence of Variostoma foraminifers, very fine peloids, ocassional
laminations, and rare bioclasts supports this interpretation (Golebiowski, 1989; Flügel and
Munnecke, 2010). At the Restentalgraben section, MF1 represents an outer ramp depositional
environment as supported by very rare bioclasts of bivalves and echinoderms, very fine-grained
skeletal debris (sample RS13) and a micritic matrix (Flügel and Munnecke, 2010).
Microfacies type MF 2 was recognized at the Restentalgraben, Eiberg, Schlossgraben and
Kuhjoch sections. The silty mudstones to marls (MF 2) deposited at the Restentalgraben section,
represent an outer ramp depositional environment deposited in a more distal part compared to MF
1. The silty mudstones to marls (MF 2) deposited at the Eiberg, Schlossgraben and Kuhjoch
sections within the Eiberg Member represent similar depositional environment to MF 1 but more
distal and likely less oxygenated due to a lack of macrofauna and presence of laminated, darker
organic-rich sediments with higher siliciclastic input (Fig. 20C, E). MF 2 sediments across the
Tiefengraben Member were deposited in the same depositional environment as MF 1 as well but
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we attribute lower carbonate content and higher siliciclastic input within MF 2 microfacies to
increased humidity and the calcification crisis associated with the end-Triassic mass extinction.
Microfacies type MF 3 was recognized at the Restentalgraben, Eiberg, Juifen,
Shlossgraben and Kuhjoch sections. The bioclastic wacke- to packstone (MF 3) deposited within
the sections across the Eiberg basin represents calciturbiditic deposits as indicated by stylolites
(Fig. 21 G-H), fragmented bioclasts, poor sorting, occurrence of basinal nodosariid foraminifera,
fine peloids and mixed fauna (Golebiowski, 1989; Flügel and Munnecke, 2010; Mette et al., 2019).
MF 3 at the Restentalgraben section was deposited within the proximal part of an outer ramp as
evidenced by the presence of normal marine diverse benthos including brachiopods, bivalves,
gastropods, echinoderms, corals and ostracod fragments (Fig. 26) (Flügel and Munnecke, 2010).
Bioclasts are characterized by various degree of fragmentation from whole to highly fragmented
shells (Fig. 21B).
Microfacies type MF 4 was recognized only at the Restentalgraben section (Fig. 22, 26).
MF 4 consists of reef derived material including corals, echinoderms, bivalves, gastropods,
bryozoans, and the benthic agglutinated foraminifera Glomospira sp. Glomospira sp. is common
in platform and back reef carbonates while Triasina sp. is widely distributed in open marine far-
reef platform carbonates (Flügel and Munnecke, 2010). Nodosariid Lagenida occupy a range of
environments from shallow to deep-water as deep as the bathyal zone (Bolotoskoy and Wright,
1976; Dubicka et al., 2018). MF4 was deposited in an intraplatform basin adjacent to coral reefs
between fair-weather and storm-weather wave base, in a mid-ramp depositional setting as
evidenced by the mixed assemblage of reef derived material (Fig. 22B, F) with the deeper water
foraminifer Triasina (Fig. 22H), imbricated shells, and intercalated rudstone with fine-grained
packstone, indicating a sudden change in energy regimes (Fig. 22C).
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Microfacies type MF 5 was recognized only at the Restentalgraben section (Fig. 23, 26).
Grainstone facies were likely deposited at the margin of carbonate sand bars in the high-energy
environment adjacent to backreef sands as evidenced by rounded grains and phosphatized clasts,
ooids, and mud clasts, along with reef derived material consisting of corals, the shallow water
foraminifer Glomospirella sp., echinoderms, sponge spicules and bivalve shells (Golebiowski,
1989; Flügel and Munnecke, 2010). A micritized coating corroborates deposition in a shallow
environment (Fig. 23) (Flügel and Munnecke, 2010).
4.6.2 Evolution of facies and environments through time
Sediments of the Kössen Formation Eiberg Member record recurring changes from
siliciclastic organic-rich shales and marls into carbonate-dominated facies documenting sea-level
fluctuations, as well as climatic and ecological changes (e.g., Golebiowski, 1998, 1990; 1991;
Holstein, 2004; Tomasowych, 2006a; Ruhl et al., 2010; Hillebrandt et al., 2013; Richoz and
Krystyn et al., 2015; Galbrun et al., 2020; Rizzi et al., 2020; Pálfy et al., 2021). The Eiberg site is
the only studied section that records the deposition of the lower three Units within the Eiberg
Member deposited in the basin, therefore further description of the lower part of the Eiberg
Member will be based on this one section. Interpretation of facies evolution across the Eiberg
Member is in accordance with previously described facies by Golebiowski (1989, 1991) where
facies deposited in the center of the Eiberg Basin are represented by a detrital mud carbonate realm.
Overall, the Eiberg section is dominated by microfacies type MF 1 representing authochtonous
sediments deposited under low-energy condition with slow sedimentation in a deeper basinal
environment. Unit 2 is characterized by relatively diverse fossil content and presence of MF 1, 2
and 3 deposits representing the shallowest part of the section (e.g., Golebiowski et al., 1989, 1991;
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Korte et al., 2017). Unit 3 records the deepening of the basin with the deepest part of the section
deposited in the lower part of Unit 3 as evidenced by predominant occurrence of micritic
mudstones (MF 1) intercalated with organic-rich shales and marls with low fossil content (Fig.
14D, 25) and by suboxic conditions (Mette et al., 2012).
At the Eiberg section, Unit 4 is dominated by carbonate mudstones (MF 1) interbedded
with thin beds of marl. The four uppermost meters of the Eiberg section are characterized by
interbedded silty marls and marls topped by the T-bed capturing the initial phase of the ETE (Fig.
25) (e.g., Hillebrandt et al., 2013; Richoz and Krystun, 2015; Mette et al., 2016; Galbrun et al.,
2020). In contrast, Unit 4 at Juifen (Fig. 11), Schlossengraben (Fig. 9) and Kuhjoch (Fig. 7) is
predominantly characterized by bioclastic wacke- and packstones (MF 3) overlying organic-rich
black shales (Fig. 7, 8E, 9, 11). At Juifen, fine-grained siliciclastic-rich sediments were likely
deposited between 2 and 4 meters based on the weathering profile (Fig. 11). Since the Eiberg
section was deposited in the deepest part of the basin compared to the rest of the studied sections
where marly deposits reflect autochthonous sediments with in-situ fauna when compared to
transported calciturbidites (MF 3), we propose that the uppermost part of the Eiberg section
captures an undiluted record of marine conditions that existed in the center of the basin right before
the onset of the ETE and sea-level fall.
MF 2 deposited at the Schlossgraben and Kuhjoch sections within the Tiefengraben
Member of the Kendlbach Formation record sedimentological and ecological change as a result of
sea-level fluctuations and the onset of the end-Triassic mass extinction. The rapid addition of
isotopically light carbon to the atmosphere and ocean by volcanic outgassing of CAMP and a
release of methane clathrates (e.g., McElwain et al., 1999; Ruhl et al., 2010; Bonis et al., 2010;
Paris et al., 2012; Bachan and Payne, 2016; Marzoli et al., 2018; Heimdal et al., 2020) initiated
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ocean acidification and climatic changes causing environmental stress and subsequent collapse in
marine primary productivity. The demise of the Dachstein carbonate platform associated with
ocean acidification caused a gap in carbonate sediment production and preservation (e.g., Schlager
and Schollnberger, 1974; Golebiowski, 1991; Ruhl et al., 2010; Kiessling and Danelian, 2011;
McRoberts et al., 2012; Greene et al., 2012; Palfy et al., 2021) while concurrent change to a more
humid climate led to higher terrestrial input within the Tiefengraben Member (Hallam, 1981;
Golebiowski, 1991; Ruhl et al., 2010; Bonis et al., 2010). The presence of pyrite nodules (Fig. 4B),
strings of pyrite (Fig. 10B), and an increase in goethite framboids and total organic carbon values
(TOC) (Bonis et al., 2010; Ruhl et al., 2010) within the lowermost part of the Tiefengraben
Member suggest anoxic bottom water conditions (Bonis et al., 2010; Ruhl et al., 2010; Hillebrandt
et al., 2013; Mette et al., 2016). Bonis et al. (2010) suggest that increased terrestrial run-off due to
increased humidity enhanced erosion and delivery of nutrients and TOC into the basin fostering
decreased salinity of the surface waters as evidenced by an acme of green algae (Cymatiosphaera)
that subsequently led to stratification of the water column and anoxic bottom water conditions.
Sea-level drop coinciding with the transition from the Eiberg Member to the Tiefengraben
Member culminated with the Schattwald Beds leading to emersion of the adjacent shallow water
areas (Hillebrandt et al., 2013; Krystyn et al., 2005; Richoz and Krystyn, 2015; Mette et al., 2016).
Since the basin reached up to 300 m water depth in the late Rhaetian it was not significantly
affected by sea level fall (Richoz and Krystyn, 2015). Lack of hiatuses and evidence for
sedimentological change above the Schattwald Beds as sea level rose corroborate this hypothesis.
Cessation of carbonate production, an increased terrestrial input, anoxia and a
collapse/restructuring of the benthic marine community highlight the unique nature of sediments
present within the Tiefengraben Member where MF 2 sediments are deposited. We propose that
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MF 2 sediments across the Tiefengraben Member were deposited in the same depositional
environment as MF 1 but MF 2 contains lower carbonate content and higher siliciclastic input as
a result of increased humidity and the calcification crisis.
The Restentalgraben locality spans all 5 microfacies types. The three lowermost meters of
the section are dominated by grainstone beds (MF 5) and represent the shallowest part of the
section deposited at the margin of carbonate sand bars. The deepest part of the section is recorded
right above the grainstone beds up to the -10 m horizon as evidenced by siliciclastic-dominated
facies of organic-rich shales and marls interbedded with thin limestone beds (Fig.17B; 26). This
part of the section was deposited predominantly below storm-weather wave base within a more
distal part of the outer ramp. The covered horizon between -14 and -20 meters is likely a result of
weathering of soft fine-grained siliciclastic sediments such as marls and shales (Fig. 26). Unit 4 is
characterized by carbonate dominated facies of bioclastic pack- and rudstone (MF 4) suggesting
shallowing-up of the section which is in congruence with the sections deposited in the basin center
(Fig. 26). Unit 4 was deposited in a mid-ramp depositional setting behind the small carbonate
platform “Oberrhaet Limestone”.
4.6.3 Faunal distribution.
The Eiberg Member is characterized by diverse groups of bivalves dominated by Chlamys
sp. and followed by relatively diverse rhynchonellata brachiopods dominated by Fissirhynchia
fissicostata (Fig. 29). Ammonoids are restricted to one genus of Choristoceras. Both the bivalve
Chlamys and the brachiopod Fissirhynchia are epifaunal suspension feeders where Chlamys
represents mobile and Fissirhynchia represents stationary modes of life (Fig. 29). Additionally,
echinoderm fragments are abundant in thin-sections both within the basin center as well as at
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Restentalgraben. Echinoderms are stenohaline sessile organisms which are indicative of persistent,
normal marine salinity conditions (Richoz et al., 2012). Overall, macrofaunal assemblages across
the Eiberg Member are representative of fully marine conditions present in the Eiberg Basin as
well as within a small intraplatform (“Oberrhaet Limestone”) deposited during the upper Rhaetian.
Unit 4 captures the time period right before the onset of the ETE and the very top of Unit
4 (bituminous layer) records the initial phase of the extinction event. The lowermost part of the
Kuhjoch and Schlossgraben sections records organic-rich fissile black shale deposits containing
pyrite nodules which are indicative of suboxic conditions within this interval (Fig. 8E). Yet, the
uppermost part of the Eiberg Member is dominated by a return to a carbonate regime as
documented at the Kuhjoch, Juifen and Schlossgraben sections (Fig. 7-12). A shift towards
carbonate deposits right before the onset of the ETE is likely controlled by sea-level fall (e.g.,
Golebiowski, 1989, 1990; Ruhl et al., 2010; McRoberts et al., 2012; Hillebrandt et al., 2013; Palfy
et al., 2021). Carbonate facies record diverse facies elements including bivalves, brachiopods,
echinoderms, ostracods and foraminifers signifying the presence of a healthy benthic marine
community right before the onset of the ETE (Fig. 7-12).
The deepest Eiberg section documents a diverse fauna 30 cm below the bituminous layer
deposited within silty marls. Although, the Eiberg section is quite depauperate across Unit 4 based
on petrographic and faunal analysis, the horizon right below the top of the T-bed documents a
diverse bivalve assemblage with 1 choristoceratid ammonoid and the highest functional diversity
(5 modes of life) observed in the section (Fig. 25). Bulk analysis of the RS1 bed at the
Restentalgraben section, the interval right below the T-bed, didn’t produce fruitful results in terms
of identifiable specimens, nevertheless, thin-sections record bioclastic packstone (MF 4) rich in
bivalve and echinoderm bioclasts with coral, brachiopod and gastropod fragments (Fig. 22A-B,
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Fig. 26) indicating the presence of an ecologically diverse and trophically complex marine
ecosystem in the shallow water platform (McRoberts et al., 2012). Overall, macrofaunal and
microfacies analyses demonstrate the persistence of a robust marine benthic community across
different facies and water depths all the way up to the end-Triassic mass extinction in the Northern
Calcareous Alps.
The top few cm of the T-bed, the bituminous layer, records the onset of the end-Triassic
extinction as evidenced by the last occurrence of the last Triassic ammonoid Choristoceras marshi
(Fig. 12D) (Hillebrandt et al., 2013; McRoberts et al., 2012), the negative initial carbon isotope
excursion (Korte et al., 2018), increased TOC (Ruhl et al., 2009, 2010; Bonis et al., 2010) and a
mineralogical composition suggestive of mafic volcanic ash fallout derived from CAMP
volcanism (Pálfy and Zajson, 2012; Percival et al., 2017). McRoberts et al. (2012) investigated an
episodic macrofaunal bivalve assemblage occurring for the first time within the top of the T-bed
(initial extinction), persisting through the Grenzmergel interval and terminating at the peak of the
extinction within the Schattwald Beds, attesting to the severity of the extinction. These
assemblages are interpreted as eurytopic bivalve opportunistic paleocommunitites that flourished
during the initial extinction phase exploiting newly vacated habitats (McRoberts et al., 2012).
The opportunistic bivalve assemblage of the T-bed from our study corresponds well with
the McRoberts et al. (2012) account where the bivalve fauna consists of the infaunal heterodont
Cardinia hybrida (Fig. 12G), the epibyssate pectinoids Agerchlamys textoria and Pseudolima cf.
hettangiensis (Fig. 15A), and the epibyssate pterioid Meleagrinella sp. (Fig. 12F-E). In addition
to the assemblage described above, this study identified the epifaunal pectinoid Chlamys
valoniensis within the bituminous layer at the Juifen section. The faunal assemblage of the
bituminous layer at the Restentalgraben section documented by McRoberts et al. (2012) differs
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from the documented benthic assemblage of this study where it is characterized by infaunal
carditids Myophoriopis? isoceles, Palaeonuculana sp., an epifaunal pectinid Placunopsis sp.?, an
epifaunal ostreid Rhaetavicula sp., and the infaunal lucinid Schafhaeutlia sp. (Fig. 16, 18 D-E).
Although the top of the T-bed at Restentalgraben was packed with bivalve shells, crinkle
laminations and the compacted nature of sediments made it difficult to extract whole identifiable
specimens (Fig. 4A-B; 18E). Thus, the discrepancy between our and the McRoberts et al. (2012)
data could be possibly attributed to taphonomic bias at this locality.
Species turnover rates between the T-bed and sediments below were evaluated only at the
Eiberg and Restentalgraben sections. Although representing different parts of the basin, both
localities show 82% turnover rate driven by the gain of new species with 55% and 64%
appearances at the Eiberg and Restentalgraben sections respectively (Table 2; Fig. 27-28). This
pattern indicates the sudden restructuring of the benthic ecosystem since the T-bed interval
represents a short period of time. The 75% turnover rate driven by a high gain of species of 55%
is documented between the shallow water sequences of Unit 2 and the transition to the deep water
sequences of Unit 3 characterized by low oxygen conditions similar to the T-bed.
4.6.4 Implications for the end-Triassic mass extinction in the Northern Calcareous Alps.
The severe biotic crises in the Tethys as well as globally during the ETE is mainly
associated with global warming (e.g., Korte et al., 2009; Bonis and Kurschner, 2012; Ruhl et al.
2010, 2020; Pálfy and Kocsis, 2014), ocean acidification (e.g., Greene et al., 2012; Hönisch et al.,
2012; Ikeda et al., 2015), sea-level change (Hallam, 1981) and ocean anoxia (e.g., Bonis et al.,
2010; Jaraula et al., 2013; Atkinson and Wignall, 2019; Larina et al., 2019; Fujisaki et al., 2020).
Additional triggers that played a role in the west-Tethyan region are associated with reduced
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salinity (Bonis et al., 2010; McRoberts et al., 2012) where enhanced seasonality as a result of
global warming induced runoff and erosion of the hinterland that caused reduced salinity leading
to an acme in green algae and stratification of the water column (Ruhl et al., 2010; Bonis et al.,
2010; Hillebrandt et al., 2013).
The suboxic to anoxic conditions are apparent within the T-bed as indicated by an increase
in TOC, fine-laminated organic-rich sediments, increase in green algae production and pyrite
nodules (Fig. 4B). The McRoberts et al. (2012) study questioned the role of anoxia during the
initial phase of the extinction in the NCA predominantly due to the presence of epifaunal and
shallow burrowing taxa and the terrestrial source of organic matter instead of a link to marine
productivity. Yet, the anoxic marine conditions should not be ruled out as a trigger for the marine
ecosystem collapse in the Eiberg Basin despite the presence of infaunal and epifaunal taxa within
the T-bed and the Grenzmergel interval due to multiple lines of evidence in support of suboxic
conditions in the basin as described above. Seasonal anoxic and hypoxic conditions have been
observed in modern coastal environments (May 1973, Santos and Simon 1980, Jørgensen 1990,
Babenerd 1991, Prena 1994; Lechuga-Devéze et al., 2001; Tomasowych et al., 2017) resulting in
intensified water stratification from early spring to autumn and a well-mixed water column during
the winter (Lechuga-Devéze et al., 2001). For example, in the Adriatic Sea, seasonal water column
stratification facilitated the change in marine ecosystems toward dominance of fast-growing
opportunistic species (Di Camilo and Cerano, 2015; Tomasowych et al., 2017). An enhanced
seasonality that subsequently led to salinity stratification and anoxic bottom water conditions
(Ruhl et al., 2010; Bonis et al., 2010) likely was episodic allowing the opportunistic benthic fauna
to recolonize the sea-floor in between deoxygenated periods especially during the initial phase of
the extinction.
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Using mineralogical composition of episodic opportunistic bivalve assemblages occurring
within the T-bed and the Grenzmergel interval, McRoberts et al. (2012) proposed that ocean
acidification is the most plausible scenario for an extinction in the Tethys that is consistent with a
global carbonate gap in the sedimentary record at the ETE (e.g., Greene et al., 2012; Hönisch et
al., 2012; Ikeda et al., 2015; Pálfy et al., 2021). A dominance of noncalcareous, siliceous
foraminifers at the base of the Tiefengraben Member corroborates the ocean acidification scenario
for the extinction (Clemence et al., 2010; McRoberts et al., 2012; Hillebrandt et al., 2013).
Carbonate as well as siliciclastic facies deposited right below the top of the T-bed or the
onset of the end-Triassic mass extinction in the Eiberg Basin record a robust paleoecommunity
with a diverse ecological structure. The faunal, mineralogical and sedimentological composition
of the bituminous layer (the top of the T-bed) captures sudden ecological shifts where eurytopic
opportunistic bivalves proliferated exploiting newly vacated niches of the early extinction phase
(McRoberts et al., 2012). The sudden tempo of extinction documented in the Tethys basin differs
from a more gradual extinction scenario documented in the northeastern Panthalassic basin (Larina
et al., 2021). In northeastern Panthalassa, precursor perturbations of the carbon cycle and evidence
of punctuated anoxic conditions preceding the ETE initiated restructuring of shallow marine
benthic ecosystems towards overall lower diversity including more dominant low oxygen tolerant
taxa with the first appearance of chemosymbiotic lucinids in the area (Larina et al., 2021). A
different tempo of extinction in the Panthalassic basin could potentially explain why the fauna was
more severely affected in Panthalassa than in the Tethys during the end-Triassic mass extinction
(Dunhill et al., 2017).
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4.7 Conclusions
• Microfacies and macrofaunal analyses of the upper Rhaetian strata, Eiberg Member of the
Kössen Formation, demonstrate the presence of an ecologically diverse and trophically
complex marine ecosystem within the shallow water platform “Oberrhaet Limestone”. In
the basin center, deeper water environments are characterized by a less complex trophic
marine ecosystem, mainly dominated by bivalves and brachiopods, but still ecologically
diverse and robust right before the extinction.
• Overall, this study demonstrates the persistence of a robust marine benthic community
across different facies and water depths right before the onset of the end-Triassic mass
extinction in the Northern Calcareous Alps.
• In the Tethys, the combination of reduced salinity, episodic anoxia/hypoxia and ocean
acidification caused the sudden ecological crisis during which the pre-extinction marine
ecosystem collapsed allowing opportunistic paleoecommunities to occupy vacant niches.
During the initial extinction phase, eurytopic opportunistic paleocommunities flourished
followed by their demise during the main phase of the extinction as environmental
conditions worsened due to CAMP volcanic activity (McRoberts et al., 2012; Hillebrandt
et al., 2013).
• Documented ecological shifts in the Tethys region reveal the sudden tempo of ecological
changes in the Tethys during the ETE in contrast to the more gradual nature of ecological
shifts documented in the Panthalassic basin (Larina et al., 2019, 2021).
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Figures and Tables Chapter 4
Figure 1. A) simplified paleogeographic reconstruction of the Tethys ocean during Late Triassic;
B) the northwest Tethyan region during the Rhaetian showing the paleolocation of the Northern
Calcareous Alps in the black box; C) NW-SE cross-section of the Eiberg Basin. Modified after
Ruhl et al. (2009) and Rizzi et al. (2020).
W
Northern Calcareous Alps
E
Dachstein Platform
Triassic Jurassic
Norian Rhaetian
Kössen Fm
Hochalm Mb
Hauptdolomite Fm
Dachstein Fm
Eiberg Mb
Eiberg basin
Oberrhaet Limestone
Hallstatt basin
Zlambach Fm
~50 km
Restentalgraben
Kuhjoch
Juifen
Schlossgraben
Eiberg
!
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Figure 2. Stratigraphy of the Eiberg Basin of the Northern Calcareous Alps. Arrows illustrate
onlap of Kendlbach Formation on top-Rhaetian unconformity during transgressive cycle. X
symbols mark relative position of the end-Triassic mass extinction (adapted from McRoberts et
al., 2012).
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Figure 3. Chrono- and bio- stratigraphy of the Rhaetian Stage (Hochalm and Eiberg Members),
modified after Galbrun et al. (2020), Rizzi et al. (2020), and Ogg (2012).
Ammonoid Z/Subzone
Standard
Age (Ma)
Stage
Substage
Formation
Member
Litho. units
Ogg (2012)
“Short Rhaetian”
Long (2012)
“Short Rhaetian”
ICS (2019)
Galbrun et al. (2020)
205.4
209.5
208.5
208.05
201.3
±0.2
201.3
Period Upper Triassic
Rhaetian Nor.
Upp. Lower Middle Upper
Kössen Formation
Choristoceras
marshi
Choristoceras
marshi
C. ammonitiforme
Vandaites
stuerzenbaumi
Vandaites
stuerzenbaumi
Vandaites
saximontanus
Paracochloceras
suessi
Sagenites
quinquepunctatus
Conodont Zone/
Subzone
Misikella ultima
Misikella rhaetica
M. posthernsteini
M. hernsteini
Epigon. bidentata
M. posthernsteini
Epigond. bidentata
Un. 2 Unit 3 U4 U4
Hochalm Member Eiberg Mmber
Unit 3 U1 U2 1
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Figure 4. Representative examples of T-bed with bituminous layer. A) T-bed at Restentalgaren
section. Notice crinkly laminations and heavily compacted thin layers of shell material. B)
Organic-rich black T-bed at Restentalgraben section. White arrow points to pyrite nodule. C-D)
T-bed at Juifen section. D) Notice dark-colored sediments within the bituminous layer.
A
1 cm
B
T-bed
Bituminous layer
C
Bituminous layer
D
A
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Figure 5. Extinction interval spanning T-bed followed by the Grenzmergel Bed and Schattwald
Beds: A) Schlossgraben section, B) Kuhjoch section.
T-bed
Schattwald Beds
Grenzmergel Interval
Golden Spike
Triassic
Jurassic
Schwattwald
Beds
Tiefengraben Member
A B
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Figure 6. Map showing the locations of studied localities. 1) Kuhjoch (47º29’02”N, 11º31’50”E),
2) Juifen (47º32’53”N, 11º37’32”E), 3) Schlossgraben (47º28’32”N, 11º28’54”E), 4) Eiberg
(47°33’00”N, 12°10’07”E), 5) Restentalgraben (47°50’27”N, 14°32’21”E).
Germany
Switz.
Czech Rep.
Austria
Italy
Slovenia
Hungary
Innsbruck
Salzburg
Vienna
100 km
1. Kuhjoch
2. Juifen
3. Schlossgraben
4. Eiberg Quarry
5. Restentalgraben
2
4
1
5
3
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Figure 7. Kuhjoch locality. A) Stratigraphic section of the Kuhjoch section with marker beds for
thin-section samples. B) Occurrence of opportunistic bivalves from McRoberts et al. (2012). C)
Organic carbon isotope record from Ruhl et al. (2009) and Hillebrandt et al. (2013). ICIE = initial
negative carbon isotope excursion. Main CIE = main negative carbon isotope excursion. D)
Mercury and TOC data from Percival et al. (2017). E) Distribution of microfacies. MF =
microfacies.
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Figure 8. Kuhjoch locality. A) Photograph of Kuhjoch section with location of Kuhjoch West
section indicated by white line adapted from Hillebrandt et al. (2013). B) Thick-bedded
bioturbated bioclastic wackestones intercalated with occasional thin-bedded calcareous marls
within the Unit 4, Eiberg Member. C) Uppermost part of the Eiberg Member including the T-
bed. D) Transition from the Eiberg to Tiefengraben Member. E) Fissile black shale at the base of
the section. F) the Schattwald beds. C. marshi = Choristoceras marshi, P. spelae = Psiloceras
spelae tirolicum.
A
B
C
T-bed
Eiberg Member
Tiefengraben
Member
T-bed
D
E F
Eiberg Member
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Figure 9. Schlossgraben locality. A) Stratigraphic log of the Schlossgraben section with marker
beds for thin-section samples. B) Occurrence of opportunistic bivalves from McRoberts et al.
(2012). C) Organic carbon isotope record from Ruhl et al. (2009). ICIE = initial negative carbon
isotope excursion. D) Distribution of microfacies. MF = microfacies.
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Figure 10. Field photos of Schlossgraben locality. A) Thick-bedded bioclastic wackestones to
packstones intercalated with occasional thin-bedded calcareous marls within the Unit 4, Eiberg
Member. B) The Grenzmergel interval with a weathered pyrite layer (white arrow). C) Transition
from the Eiberg to Tiefengraben Member. White arrow points a weathered pyrite layer. D) The
Grenzmergel bed overlain by Schattwald beds.
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Figure 11. Juifen section. A) Stratigraphic section of the Juifen section; Green ammonite marks
the last occurrence of Choristoceras marshi at this locality. B) Macrofaunal distribution from
this study.
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166
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Figure 12. Juifen locality. A) Field photo of the Juifen outcrop. Yellow line marks the T-bed
location. B) The top of the T-bed with fossils marked by white circles. C) The cross-section
showing an articulated brachiopod within Bed 14. D) Photo of Choristoceras marshi found within
the T-bed. E) Photo of Meleagrinella sp. within the T-bed. F) Photo of the T-bed where green box
marks the location of Meleagrinella sp. depicted in (E). Scale = 1 cm. G) Photo of Cardinia
hybrida found within the top of the T-bed. Scale = 1 cm.
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Figure 13. Eiberg locality. A) Stratigraphic section of the Eiberg section with marker beds for
microfacies and macrofaunal samples. B) Organic carbon isotope record from Ruhl et al. (2009).
C) Macrofaunal distribution from this study.
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Unit 3 Unit 4
A
B C
D
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Figure 14. Field photos of Eiberg section; A) Intercalated carbonates and marls across Unit 3
and Unit 4. B) Uppermost part of the Unit 4 with an active cement quarry “SPZ Zementwerk
Eiberg GmbH” in the background. C) Upper part of unit 4. D) Black shales within the Unit 3
indicating low oxygen conditions.
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Figure 15. Photos of macrofauna found at the Eiberg section. A) Pseudolimea cf. hettangiensis
within the bituminous layer. Scale = 0.5 cm. B) Choristoceras marshi found within bed H and I.
C) Fissirhynchia fissicostata found within Bb7 bed. Scale = 1 cm. D) Zeilleria eliptica found
within Bb7 bed. Scale = 1 cm. E) Inoperna (Triasoperna) schafhaeutli found within Unit U.
Scale = 1 cm. F) Chlamys sp. found within Unit U. Scale = 1 cm.
A. Hettangeinsis Bituminous layer scale 0.5 cm
B. C. marshi between H&I scale 0.5 cm
C. scale 1 cm. fis. fis.Bb7
D. scale 1 cm Zeilleria eliptica Bb7
E. Inoperna schauefetli 1 cm scale Unit 4 Bed U
F. Chlamys sp. scale 1 cm Unit U
A B
C D
E
F
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Figure 16. Restentalgraben locality. A) Stratigraphic section of the Restentalgraben section with
marker beds for microfacies and macrofaunal samples. B) Organic carbon isotope record from
Ruhl et al. (2009). C) Macrofaunal distribution from this study
Figure 17. Field photos of Restentalgraben section; A) Intercalated carbonates and marls across
Unit 4; B) Siliciclastic-dominated facies (black marls) within the Unit 3; C) Cross-section of
gastropod within RS1 bed; D) Laminated T-bed, notice compressed shells; E) Cross-section of
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articulated brachiopods (circled in white) within RS1; F) Weathered coral branches within RS1
bed; G) Hardground RS45 bed, notice undulating surface on top of the bed.
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C
A
A.RST31C Placunopsis alpina. 0.5 cm scale
B. RS4 Chlamys sp. scale = 1 cm
C. Rhaetavicula concorta RST31C scale = 0.5 cm
D. Myophoripsis ? isoceles T-bed scale = 0.5 cm
E. T-bed Paleonuculana and bivalve cluster scale = 0.5 cm
C
B
E
D
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Figure 18. Photos of macrofauna found at the Restentalgraben section. A) Placunopsis alpina
found within RST31C bed. Scale = 0.5 cm. B) Chlamys sp. found within RS4 bed. Scale = 1 cm.
C) Rhaetavicula concorta found within RST31C bed. Scale = 0.5 cm. D) Myophoripsis ?
isoceles found within the T-bed. Scale = 0.5 cm. E) T-bed piece with the cluster of bivalves on
the surface. White arrow points to Palaeonuculana sp. Scale = 0.5 cm
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Table 1. Lithofacies types of the Eiberg and lower Tiefengraben Member and their depositional
environment.
Lithofacies Constituents Paleoenvironment Interpretations Depositional setting
MF1 - mudstone
MF2 - silty mudstone/
marl
MF3 - bioclastic wacke-
to packstone
MF4 - bioclastic pack-
to rudstone
MF5 - coated bioclastic
grainstone
Basin1/Outer ramp2 Open ocean
Fine peloids, rare fragments of
echinoderms, foraminifers,
ostracods, brachiopods and bivalves
Restentalgraben2 Eiberg, Juifen, Kuhjoch, Schlossgraben1
Goethite framboids, quartz silt
Open ocean
Basin1/Outer ramp2
“Background “ sedimentation with
influx of terragineous sediment1,2
Fall-out of “background “ pelagic
suspension1,2
Platform -
margin reefs2
Platform -
margin reefs 2
Platform - margin
and shoals2
Sand Shoal2
Echinoderms, brachiopods and
bivalves with less abundant
ostracods, foraminifers, gastropods
and ammonoid remains. Stylolites,peloids
Distal toe-of-slope1/
Outer ramp2
Suspension deposition from a low
density turbidity current1;
Benthic agglutinated (Glomospira sp.)
and hyaline (Nodosariids) foraminiferas;
gastropods, brachiopods, foraminifers,
ammonoids, corals, and bryozoans
Ooids; coral, foraminifera, sponge spicules,
echinoderm, gastropod, brachiopod,
bivalves. Stylolites.
Mid-ramp 2
High-energy environment
adjacent to backreef sands
Strongly agitated, aerated, shallow
subtidal environment
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Figure 19. Photomicrographs of Microfacies 1 – mudstone. A) Thin-section showing fine-grained
micritic matrix with fine peloids and common occurrence of sparite veins (i). The image is in cross-
polarized light, bed M, Eiberg section. B) Thin-section with occasional bioclasts. The image is in
plane-polarized light, bed E2, Eiberg section. C) Thin-section with echinoderm fragment (i). The
image is in plane-polarized light, bed 17, Eiberg section. D) Mudstone with fine-grained micritic
matrix. The image is in cross-polarized light, bed 16, Kuhjoch section. E) Mudstone with fine-
grained micritic matrix. The image is in cross-polarized light, bed RS5, Restentalgraben section.
A. Eiberd bed M with sparite veins XPL
B. Eiberg E2 with bioclasts PPL
C. Eiberg Bed 17 PPL i - echinoderm
D. Kuhjoch Bed 16 XPL
E. RS5 XPL
F. Schlossengraben Bed 2 PPL
A
500μm
500μm
iii
500μm
i
B
500μm
500μm
E
D
500μm
500μm
F
i
C
500μm
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F) Mudstone with fine-grained micritic matrix showing bioturbation. The image is in plane-
polarized light, bed 2, Schlossgraben section.
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Figure
20. Photomicrographs of Microfacies 2 – silty mudstone/marl. A) Thin-section showing
homogenous composition. The image is in cross-polarized light, bed B, Eiberg section. B) Thin-
section showing fine calcarenite-calcisiltite laminae alternate with fine quartz silt. The image is
in plane-polarized light, bed RS34, Restentalgraben section. C) Thin-section of fine-laminated
organic-rich silty marls. The image is in cross-polarized light, bed 15, Kuhjoch section. D) Thin-
section of Schattwald beds showing typical matrix saturated with reddish golden hue and quartz
silt. The image is in plane-polarized light, bed 36, Kuhjoch section. E) Thin-section showing
fine-laminations and organic-rich nature of sediments. The image is in plane-polarized light, bed
A. XPL Eiberg Bed B
B. RS34 PPL
C. Kuhjoch XPL Bed 15
D. Kuhjoch Schattwald bed PPL #36
E. Schlossen #1 PPL
F. Schlossen #13 XPL
A
500μm
C
B
500μm
500μm
D
500μm
500μm
E F
500μm
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1, Schlossgraben section. F) Thin-section of Schattwald beds showing matrix saturated with
reddish golden hue. The image is in cross-polarized light, bed 13, Schlossgraben section.
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A. RS 14. stylolites. XPL
B RS4. recrystallized brachiopod shells XPL
C. Eiberg Bb9a XPL
D. EB296. i - punctate brachiopod shell XPL
E. Bb10. ii- ammonoid phragmocone PPL
F. Bed 25 Juifen. (iii)stereom? (iv) bivalve XPL
G. Kuhjoch bed 27 XPL
H. Schlossgraben Bed 5 XPL
F
G H
A
B
500μm
500μm
C
D
i
1000μm 500μm
E
ii
500μm
iii
iv
500μm
iii
iii
500μm
500μm
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Figure 21. Photomicrographs of Microfacies 3 – bioclastic wacke- to packstone. A) Thin-section
showing sparitic ghost structures of bioclasts with small and stylolite feature (white arrow). The
image is in cross-polarized light, bed RS14, Restentalgraben section. B) Thin-section showing
brachiopod and bivalve shells replaced with sparite cement. The image is in cross-polarized
light, bed RS4, Restentalgraben section. C) Thin-section showing fine-grained bioclasts
embedded in the matrix with occasional whole valves. The image is in cross-polarized light, bed
Bb9a, Eiberg section. D) Thin-section showing fine-grained bioclasts with occasional whole
valve of punctate brachiopod shells (i). The image is in cross-polarized light, bed Bb9a, Eiberg
section. E) Thin-section showing a fine micritic matrix with the chamber of ammonoid (ii). The
image is in plane-polarized light, bed Bb9a, Eiberg section. F) Thin-section showing fine-grained
bioclasts with echinodermal stereom (iii) and whole valve of bivalve (iv). The image is in cross-
polarized light, bed 25, Juifen section. G) Thin-section showing fine-grained bioclasts with
echinodermal debris (iii). The image is in cross-polarized light, bed 27, Kuhjoch section. H) A)
Thin-section showing fine-grained bioclasts with stylolite feature (white arrow). The image is in
cross-polarized light, bed 5, Schlossgraben section.
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A. RS1 PPL (i) punctate brachs bioclatic packstone
B. RS1 PPL coral
C. RS39 PPL rudstone with fg packstone
D. rudstone RS39 PPL
E. bioclastic rudstone RS31C PPL
F. bioclastic packstone RS16T XPL (ii) coral
G. bioclastic rudstone RS6 . compacted bivalve shells
H. bioclatic packstone RS17 XPL foram (iii), echinoderm (iv)
A
500μm 500μm
B
500μm
C
500μm
D
i
i
E
ii
F
G
500μm
500μm
500μm
H
500μm
iii
iv
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Figure 22. Photomicrographs of Microfacies 4 – bioclastic pack- to rudstone. A) Thin-section
showing poorly sorted packstone with bivalve and ocassional punctate brachiopod (i) shells. The
image is in plane-polarized light, bed RS1, Restentalgraben section. B) Thin-section showing large
coral bioclast partially recrystallized with sparite and quartz silt within micritic matrix. The image
is in plane-polarized light, bed RS1, Restentalgraben section. C) Thin-section showing rudstone at
the bottom overlain by fine-grained packstone with a clear erosional boundary. The image is in
plane-polarized light, bed RS39, Restentalgraben section. D) Thin-section showing bioclastic
rudstone composed of diverse bioclasts. The image is in plane-polarized light, bed RS39,
Restentalgraben section. E) Thin-section showing bioclastic rudstone dominated by bivalve shells
recrystallized with sparite cement. The image is in plane-polarized light, bed RS31C,
Restentalgraben section. F) Thin-section showing bioclastic packstone composed of bioclasts
including coral fragments (ii). The image is in plane-polarized light, bed RS16T, Restentalgraben
section. G) Thin-section showing the parallel arrangement of bivalve shells pointing to some
current control. The image is in plane-polarized light, bed RS6, Restentalgraben section. H) Thin-
section showing diverse bioclasts including involutinid foraminifer Triosina sp. (iii) and
echinodermal fragments (iv). The image is in cross-polarized light, bed RS17, Restentalgraben
section.
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Figure 23. Photomicrographs of Microfacies 5 – coated bioclastic grainstone. A) Thin-section
showing diverse micritized skeletal grains replaced with sparite, including coral fragment (i). The
image is in plane-polarized light, bed RS45, Restentalgraben section. B) Thin-section showing
mainly rounded partially phosphatized intraclasts with diverse fauna including foraminifera (i),
sponge spicule (ii), gastropod (iii), and echinoderms (iv). The image is in plane-polarized light,
bed RS45, Restentalgraben section. C) Thin-section showing diverse bioclasts embedded in mud
clast and rounded micritized grains replaced with sparite. The image is in cross-polarized light,
A. RS45 PPL coral plus bioclasts surrounded by a thin micritic envelope micritised grains
B. RS45 PPL i- foraminifera; ii- sponge spicule iii - gastropod iv- echinoderms fragments
C. RS45 mudclast with bioclasts and micritised grains XPL .
D. RS45 XPL pressure dissolution with micritised grains i - ooid ii - stereom echinoderm
E. RS53 PPL
F. RS53 XPL
500μm
A
B
i
i
500μm
ii
iii
iv
C
500μm
i
ii
D
500μm
F
500μm 500μm
E F
i
i
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bed RS45, Restentalgraben section. D) Thin-section showing rounded partially phosphatized
intraclasts composed of ooids (i) and bioclasts (ii) with abundant pressure dissolution features (i).
The image is in cross-polarized light, bed RS45, Restentalgraben section. E) Thin-section showing
micritized coated grains embedded in sparry and partially micritic cement with quartz silt. White
arrow points to stylolite. The image is in plane-polarized light, bed RS53, Restentalgraben section.
F) Thin-section showing diverse micritized bioclasts and ooids (i) with stylolite features. The
image is in cross-polarized light, bed RS45, Restentalgraben section.
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Figure 24. Stratigraphic log of the Juifen section with marker beds, microfacies distribution (MF=
microfacies), facies elements identified during macrofaunal and microfacies analyses, faunal count
determined during macrofaunal analysis with corresponding faunal and relative abundance
paleoecological niche distribution.
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Figure 25. Stratigraphic log of the Eiberg section with marker beds, microfacies distribution (MF=
microfacies), facies elements identified during macrofaunal and microfacies analyses and
published in Mette et al. (2016), faunal count determined during macrofaunal analysis with
correspondent faunal and relative abundance paleoecological niche distribution.
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Figure 26. Stratigraphic log of the Restentalgraben section with marker beds, microfacies
distribution (MF= microfacies), facies elements identified during macrofaunal and microfacies
analyses, faunal count determined during macrofaunal analysis with correspondent faunal and
relative abundance paleoecological niche distribution.
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Table 2. Results of turnover analysis for Eiberg and Restentalgraben sections.
Time Bins Total turnover Appearance Disappearance
Eiberg (Depositional Sequences)
2 0.82 0.55 0.27
3 0.87 0.47 0.4
4 0.75 0.55 0.2
5 0.75 0.2 0.55
Restentalgraben (Parasequences)
2 0.86 0.62 0.24
3 0.72 0.11 0.61
4 0.66 0.22 0.44
Restentalgraben (Depositional Sequences)
2 0.82 0.64 0.18
3 0.72 0 0.72
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Figure 27. Sequence stratigraphic interpretation of the Eiberg section from Mette et al. (2016;
Fig. 11) with corresponding turnover results.
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Figure 28. Sequence stratigraphic interpretation of the Restentalgraben section with
corresponding turnover results.
239
Figure 29. Two-way cluster analysis of macrofaunal assemblage. Brachiopods are depicted in bold. Epif. = epifaunal; facult. =
facultatively; mob. = mobile; inf. = infaunal; susp. = suspension.
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packstone
wackestone
marl
Taxa
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Bivalve dominated assemblage (mixed lithofacies)
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(mudstone lithofacies)
Bivalve dominated biofacies (mixed lithofacies)
Cluster 1 Cluster 2 Cluster 3
3A 3B
2A 2B
Cluster 1
1A
Cluster 2 Cluster 3
1B
Rhynchonella biofacies
193
194
239
Figure 30. Nonmetric Multidimensional Scaling (=NMDS) showing samples as points. Samples
close to one another are similar in macrofaunal composition. A) Samples colored by corresponding
lithofacies. Close clustering of samples from the T-bed is observed. B) Faunal assemblages of
Eiberg and Juifen sections show clear overlap while there is a minor overlap with Restentalgraben
section.
−1.0 −0.5 0.0 0.5
−0.6 −0.4 −0.2 0.0 0.2 0.4
NMDS1
NMDS2
T-bed
packstone
wackestone
marl
mudstone
grainstone
−1.0 −0.5 0.0 0.5
−0.6 −0.4 −0.2 0.0 0.2 0.4
NMDS1
NMDS2
Eiberg
Juifen
Restenalgraben
0.8 0.6 0.4 0.2 0.0 0.2 0.4
0.2 0.0 0.2
NMDS1
NMDS2
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Restenalgraben
Juifen
Juifen
Juifen
Juifen
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
Eiberg
AltGower
stress: 0.13
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CHAPTER 5. GLOBAL BIOTIC AND GEOCHEMICAL TRENDS
LEADING UP TO THE END-TRIASSIC MASS EXTINCTION
ABSTRACT
The latest Triassic interval is characterized by multiple carbon perturbation events and
prolonged faunal extinction terminating in the end-Triassic mass extinction (ETE). This study
investigates global geochemical record and biotic changes on stage-by stage basis from Carnian to
Sinemurian using previously published literature and Paleobiology Database (PBDB). We
document major turnover of cephalopods during the Norian-Rhaetian transition, largely at the
Norian-Rhaetian boundary. However, cephalopods almost became extinct at the ETE when their
generic richness was already impoverished. Overall, the Rhaetian Stage is characterized by
reduced generic richness in marine invertebrates across the globe implying an important role of
the biotic turnover and carbon cycle perturbation event that happened at the Norian/Rhaetian
boundary. Yet, additional studies of this transition are required to fully resolve the causes and
consequences of this major reduction in biodiversity since the Rhaetian stage is complicated by
lower orgination rate and a shorter duration compared to the Norian and Carnian Stage. During the
end-Triassic mass extinction, marine fauna inhabiting the Panthalassic basin was more affected
compared to the Tethys basin likely due to the detrimental impact of pre-extinction episodic
euxinic to anoxic conditions and the post-extinction “sponge takeover” phenomenon. Despite
increased generic richness across all the basins during the Sinemurian, marine invertebrates never
reached the level of generic richness documented either during the Norian or Sinemurian Stages.
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5.1. Introduction
The Late Triassic was an interval of multiple perturbation events culminating in the end-
Triassic mass extinction (ETE). The first remarkable carbon and faunal perturbation event
occurred during the middle Carnian (between 234 and 232 Ma ago), known as the Carnian Pluvial
Episode (Dal Corso et al, 2015, 2018, 2020). The middle Carnian climate perturbation is marked
by multiple negative carbon isotope excursions (N-CIE) likely related to the emplacement of a
Large Igneous Province (LIP), called the Wrangellia Igneous Province (e.g., Dal Corso et al., 2015,
2018, 2020; Rigo et al., 2020) (Fig. 1). These shifts in the δ
13
C record coincide with major biotic
turnovers that potentially led to the emergence of the first scleractinian reefs and rock-forming
calcareous nannofossils resulting in significant changes in ocean chemistry in the Late Triassic
(Dal Corso et al., 2020).
The second significant carbon and faunal perturbation event marks the Norian/Rhaetian
boundary (NRB). The NRB is marked by a positive organic carbon isotope excursion and the last
occurrence of the bivalve Monotis (e.g., Wignall et al., 2007; Whiteside and Ward, 2011; Zaffani
et al., 2017; Rigo et al., 2016, 2020) (Fig. 1). The positive carbon isotope excursion (P-CIE) at the
NRB is preceded by a N-CIE possibly related to reduced ocean circulation (Sephton et al., 2002;
Ward et al., 2004; Rigo et al., 2020). Stepwise marine biotic extinction has been documented across
the end-Norian culminating with major ammonoid extinction, conodont turnovers, and the
extinction of the cosmopolitan and abundant bivalve Monotis at the NRB (Hallam and Wignall,
1997; Ros, 2009; McRoberts, 2010; Ros and Echevarria, 2011; Ros et al., 2011, 2012; Rigo et al.,
2020) (Fig. 1). Overall, the terrestrial extinction record is characterized by the extinction of some
tetrapods and local palynofloral turnover events but is less evident due to time correlation
complexities (Rigo et al., 2020).
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The third carbon cycle perturbation event marks the end-Triassic mass extinction and
transition from the Triassic to Jurassic periods. Similar to previous perturbation events, the ETE
is characterized by multiple carbon isotope excursion events (“precursor”, “initial”, and “main”)
(e.g., Ruhl and Kurschner, 2011; Yager et al., 2017; Zaffani et al., 2018; Fujisaki et al., 2018;
Larina et al., 2021) (Fig. 1) and major biotic crises where approximately 80% of all marine and
terrestrial species became extinct (Sepkoski 1996; Alroy et al., 2010).
The ETE had the most devastating impact on the clades that inhabit todays' oceans (so-
called Modern Fauna (Sepkoski, 1982, 1996) compared to other extinction events in the
Phanerozoic. The marine record indicates that ammonites, radiolarians and scleractinian corals
were on the brink of extinction (Guex et al., 2004; Kiessling et al., 2007). The terrestrial record
documents a high diversity loss in sporomorphs, early Mezosoic vertebrates, and plants (McElwain
et al., 1999; Davies et al., 2017). Dunhill et al. (2017) investigated the effects of the ETE on
functional diversity and composition of marine ecosystems using the Paleobiology Database.
Despite the severe loss of species, all functional groups persisted through the ETE with high
selectivity against sessile suspension feeders and calcareous fauna in tropical latitudes (Dunhill et
al., 2017; Greene et al., 2012; Kiessling et al., 2007). Several studies emphasized that changes in
marine and terrestrial ecosystems preceded the onset of the ETE and revealed a stepwise extinction
pattern for the ETE (Bond and Wignall, 2008; Mander et al., 2008; Whiteside and Ward, 2011;
Lindström et al., 2012, 2017, 2021; Lucas and Tanner, 2018; Karádi et al., 2020; Larina et al.,
2021; Rigo et al., 2020).
The initiation of the ETE is predominately linked to CO2 and CH4 induced environmental
changes as a result of Central Atlantic Magmatic Province (CAMP) volcanic activity (e.g., Jaraula
et al., 2013; Thibodeau et al., 2016; Korte et al., 2019). Some studies propose that the amount of
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isotopically-light carbon solely derived from CAMP volcanic degassing is insufficient to account
for the negative carbon isotope shifts as large as -6‰ based on end-Triassic carbon cycle modeling
(Paris et al., 2012; Bachan and Payne, 2016; Heimdal et al., 2020). Other proposed mechanisms
include release of marine clathrates as a result of warming climate (Beerling and Berner, 2002;
Ruhl et al., 2011; Korte et al., 2019) and/or degassing of volatile-rich sediments as a result of
CAMP intrusive activity that preceded the main phase of CAMP volcanism (Ruhl and Kürschner,
2011; Davies et al., 2017; Heimdal et al., 2020).
Datasets covering pre-extinction conditions and performing comparative analysis between
the basins leading up to the ETE are very sparse (Rizzi et al., 2020; Rigo et al., 2020). Recent
studies of the pre-extinction interval show that (1) climate differed between the Panthalassic and
Tethys oceans resulting in dissimilarity between carbon isotope compositions in ocean water
chemistry (Ruhl et al., 2020), (2) punctuated anoxic to euxinic conditions existed in the
Panthalassic ocean causing the restructuring of marine ecosystems before the onset of the ETE
(Kasprak et al., 2015; Schoepfer et al., 2016; Larina et al., 2019, 2021), and (3) marine ecosystems
were thriving in the Tethys basin all the way up to the ETE in contrast the Panthalassic basin
(Larina et al., 2021). Thus, constructing paleoecological and paleoenvironmental pre-extinction
conditions provides an imperative baseline for understanding spatial and temporal trends during
one of the major mass extinction events in the Phanerozoic. This study attempts to synthesize
published data of geochemical and faunal datasets combined with a new biotic analysis in order to
establish global trends leading up to the end-Triassic mass extinction event.
5.2. Biotic turnovers of benthic paleoecology
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Marine invertebrates are widely used for evaluation of diversity and evolutionary dynamics
through time because they are very diverse and abundant and their hard parts have high
preservation potential (e.g., Sepkoski,1982, 1996; Alroy, 2008; Kiessling and Aberhan, 2007).
This study focuses on spatial and temporal distribution of the classes Bivalvia, Cephalopoda, and
Gastropoda and phylum Brachipoda across the Late Triassic to Early Jurassic since these marine
invertebrates played a major role in Late Triassic marine ecosystems. These marine invertebrates
were the main constituents in Late Triassic marine basins from the Carnian to Rhaetian Stages
with Bivalvia representing 20%, Cephalopoda representing 13%, Rhynchonellata 10%, and
Gatropoda 9% out of all Kingdom Animalia (Fig. 2).
A database of all marine animal genera from the classes Bivalvia, Cephalopoda, and
Gastropoda and phylum Brachipoda was downloaded from the Paleobiology Database (PBDB).
This database consists of 17739 occurrences of 1160 genera composed at the stage level. Ichnotaxa
and any uncertain generic assignments were excluded from the analysis. This study evaluates
fluctuations in marine invertebrate occurrences and generic richness through time in the Boreal,
Panthalassic and Tethys basins (Fig. 4-7).
Results. –– Biodiversity data of all analyzed taxa show a stepwise decrease towards the
Triassic/Jurassic boundary with the highest generic richness during the Carnian Stage (614 genera)
followed by a 16% decline during the Norian (515 genera) and the lowest generic richness during
the Rhaetian (263 genera), a 49% decline when compared to the Norian (Fig. 4A). The transition
between the Rhaetian and Hettangian is characterized by a slight decline of 14% (226 genera)
followed by a 36% increase in the Sinemurian (307 genera) (Fig. 4A).
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When this dataset is compared between basins, a different trend emerges. During the
Carnian-Norian transition, generic richness increases by 14% (193 to 220 genera) in the
Panthalassa basin and by 9% (57 to 62 genera) in the Boreal basin. In contrast, the Tethys basin is
characterized by a significant drop in generic richness of 41% (558 to 332 genera), implying
significant paleoenvironmental perturbations or changes in the Tethys region, where all studied
marine invertebrates underwent a decline (Fig. 4A; 5C). Especially, marine gastropods were
severely affected, with a documented decline of 78% and no sign of recovery even during the
Sinemurian Stage/Lower Jurassic (Fig. 5C).
Generic richness during the Norian-Rhaetian transition uniformly plummeted across the
basins with a 60% (220 to 187 genera) decline in Panthalassa, a 53% (332 to 157 genera) drop in
Tethys and a 63% (62 to 23 genera) fall in the Boreal basin. During the Rhaetian-Hettangian
transition, generic richness rises by 6% (157 to 167 genera counts) in the Tethys basin and by
113% (23 to 49 genera) in the Boreal basin while it drops by 2% (87 to 85 genera) in Panthalassa
(Fig. 4A). The observed pattern during the Triassic/Jurassic transition in the Panthalassa basin is
predominately driven by disappearance of Gastropoda and a significant drop in Brachiopoda in
contrast to Cephalopoda and Bivalvia, which diversified during the Hettangian Stage (Fig. 5B).
The Hettangian-Sinemurian transition exhibits an increase in generic richness by 73% (85 to 147
genera) in the Panthalassa basin and by 27% (167 to 212 genera) in the Tethys basin in contrast to
a fall by 31% (49 to 34 genera) in the Boreal basin.
During the Carnian-Norian transition, generic richness decreased by 3% (123 to 119
genera) in Brachiopoda, by 2% (157 to 154 genera) in Cephalopoda and by 50% (202 to 100
genera) in Gastropoda with an 8% increase (132 to 142 genera) in Bivalvia. Similar trends in
generic richness between the basins during the Norian-Rhaetian transition are observed between
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the taxa. During the Norian-Rhaetian transition generic richness uniformly plummeted across the
taxa with 56% (119 to 54 genera) in Brachiopoda, 13% (142 to 123 genera) in Bivalvia, 78% (154
to 34 genera) in Cephalopoda and 46% (100 to 54 genera) in Gastropoda (Fig. 4B). The Rhaetian-
Hettangian transition is characterized by a decline in Brachiopoda by 33%, in Bivalvia by 19%
and in Gastropoda by 15%. An increase by 32% (34 to 45 genera) is documented in cephalopods
(Fig. 4B). During the Hettangian-Sinemurian transition, generic richness uniformly increased in
all taxa with Brachiopoda by 66%, Bivalvia by 4%, Cephalopoda by 100%, and Gastropoda by
20%. Gastropoda went through a steady decline from Carnian to Hettangian with a slight recovery
during the Sinemurian Stage. Overall, all taxa recovered during the Sinemurian Stage, but never
reached the level of generic richness as observed during the Carnian Stage (Fig. 4B).
Generic biodiversity trends of analyzed taxa correspond well with trends in generic
abundances (Fig. 4-7).
5.3. Paleoenvironmental trends during the Late Triassic
Carbon and oxygen isotope geochemistry provides important insights into the evolution of
ocean water chemistry, climate dynamics, oxygenation, and productivity of past marine
environments. In particular, sudden deviations in the carbon isotope record are interpreted as
evidence of paleoclimatic and paleoenvironmental perturbations including the Late Triassic
record.
Carnian. – The middle Carnian is characterized by profound climate change associated
with multiple carbon cycle perturbations and biotic crisis. This Carnian Pluvial Episode (CPE) is
marked by global warming leading to pronounced enhancement of hydrological cycling (Tanner
et al., 2018; Dal Corso et al., 2015, 2020). Increased precipitation led to continental runoff and an
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increased nutrient influx to marine basins resulting in subsequent anoxic conditions (Dal Corso et
al., 2015; 2020). Up to four negative carbon isotope excursions (NCIE) are recognized across the
CPE. The repeated injections of
13
C-depleted carbon into the ocean-atmosphere system likely
increased the pCO2,triggering global warming events leading to increased precipitation (Dal Corso
et al., 2018; 2020). The primary source of
13
C-depleted carbon influx during the CPE is still
unresolved, but the eruption of a Large Igneous Province, the Wrangellia Igneous Province, is
considered as the most plausible scenario (e.g., Dal Corso et al., 2015, 2018, 2020; Rigo et al.,
2020) (Fig. 1).
Norian. – During the Norian Stage, the climate was mainly arid due to weakening of the
monsoonal system (Tanner et al., 2018). In the Tethys realm, arid climate triggered widespread
and pervasive dolomitization of carbonate platforms and formation of evaporitic facies (Berra et
al., 2010; Berra, 2012; Berra and Angiolini, 2014). A shift towards humid conditions is
documented during the Late Norian resulting in a cessation of dolomitization in the Western
Tethys and an increase in siliciclastic deposits (Berra et al. 2010; Berra, 2012).
Published carbon isotope data of the Norian Stage reveals an NCIE followed by a P-CIE
at the Norian-Rhaetian Boundary. This trend has been linked to reduced circulation of ocean waters
(Sephton et al., 2002; Ward et al., 2004; Wignall et al., 2007;) and coincides with major faunal
turnover (Rigo et al., 2020). The cause behind these carbon and faunal perturbations is unclear.
The following triggering mechanisms have been proposed for the documented changes across the
NRB: 1) substantial greenhouse gas emissions from an unknown LIP predating the NRB or 2) a
large bolide impact that initiated a large-scale greenhouse gas emission event (Rigo et al., 2020).
Rhaetian. – The Rhaetian Stage is characterized by multiple carbon cycle perturbations
recorded in different basins. The lowest P-CIE of 3‰ during the Rhaetian Stage is documented in
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the Tethys (Eiberg Basin) almost near the Norian/Rhaetian boundary (Rizzi et al., 2020). The
global significance of this P-CIE has yet to be determined by carbon isotope studies from different
parts of the globe.
In the Panthalassa basin, Yager et al. (2017) performed a detailed study of δ
13
Corg and
δ
13
Ccarb shifts across Late Triassic and Early Jurassic-aged strata in Levanto, Peru and coupled
observed changes with previously dated ash beds. Their analysis reveals a P-CIE of 2‰ predating
the major pulses of CAMP dated from North America by 285 ± 90 kyr. This P-CIE was correlated
with other sections around the globe corroborating carbon cycle perturbation at a global scale.
Yager et al. (2017) suggest that CAMP eruptions began earlier than previously thought or that the
pre-extinction carbon cycle perturbation is related to a different mechanism other than CAMP.
The Late Rhaetian carbon cycle perturbation includes the so-called precursor negative
carbon isotope excursion (“precursor” CIE). The precursor CIE has been recently documented in
a few sections across the Panthalassa and Tethys basins preceding the ETE by ~100,000 kyr,
although exact timing is yet to be resolved (Hesselbo et al., 2004; Ruhl and Kürschner, 2011; Dal
Corso et al., 2014; Bottini et al., 2016; Zaffani et al., 2018; Larina et al., 2021). This “precursor”
CIE is of short duration and of 1-3‰ magnitude suggesting the disruption of the ocean-atmosphere
carbon pool prior to the ETE. Larina et al. (2021) documented an increase in sulphidic sediments
associated with the precursor CIE in Eastern Panthalassa followed by restructuring of marine
benthic ecosystems towards overall lower diversity and predominance of low oxygen tolerant taxa
preceding the ETE. Larina et al. (2021) propose that environmental conditions started to deteriorate
preceding the main phase of CAMP volcanism, at least in the Panthalassic ocean. Overall, several
studies are in agreement that the “precursor” CIE was likely initiated by CAMP dyke and sill
intrusions into organic-rich sediments, possibly the Kakoulima intrusion in Guinea, preceding the
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ETE by ~100,000 years (e.g., Ruhl and Kürschner, 2011; Dal Corso et al., 2014; Davies et al.,
2017; Marzoli et al., 2018; Heimdal et al., 2020; Larina et al., 2021; Lindström et al., 2021).
The culmination of the Rhaetian Stage is marked by the “initial” carbon isotope excursion
(ICIE) followed by a P-CIE documented worldwide (e.g., Hesselbo et al., 2002; Hillebrand et al.,
2013; Bachan and Payne, 2016; Thibodeau et al., 2016; Yager et al. 2017; Petryshyn et al. 2020;
Ruhl et al., 2011, 2020; Lindstrom et al., 2017, 2019, 2021; Larina et al., 2020). The ICIE coincides
with the ETE and is temporally linked to the main phase of CAMP volcanism (e.g., Thibodeau et
al., 2016; Yager et al., 2017; Ruhl et al., 2020). The magnitude of the ICIE differs between basins
with a 4-6.5‰ magnitude in European marine basins and 2-3‰ magnitude in the Panthalassic
ocean (e.g., Thibodeau et al., 2016; Yager et al., 2017; Ruhl et al., 2020). These discrepancies in
carbon isotope records have been attributed to extreme aridity across the western Pangean
landmass causing lower delivery of organic carbon to the eastern Panthalassic basins compared to
a humid climate across the central Pangean landmass facilitating increased influx of marine and
terrestrial sources of organic matter to the Tethys basin (Bonis et al., 2010; Ruhl et al., 2020).
In addition to pre-extinction carbon cycle disturbances, there is evidence of photic zone
euxinia documented in Panthalassic and Tethys basins preceding the ETE (Kasprak et al., 2015;
Schoepfer et al., 2016; Blumenberg et al., 2016; Larina et al., 2019, 2021). In northeastern
Panthalassa, stratification and episodic euxinic-anoxic conditions are documented in deep
(Kennecott Point, British Columbia) (Kasprak et al., 2015; Schoepfer et al., 2016) as well as in
relatively shallow (Williston Lake, British Columbia) (Larina et al., 2019) water environments
preceding the ETE by ~500,000 years. In eastern Panthalassa (Ferguson Hill, Nevada),
deoxygenation events are documented at first across the “precursor” CIE and then a few meters
below the ICIE persisting all the way up to the ETE (Larina et al., 2021). In the Rhaetian ocean,
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Blumenberg et al. (2016) report anoxic conditions in the middle Rhaetian suggesting perturbation
in the biogeochemical cycles of sulfur and carbon long before the major mass extinction event.
Although, there is no evidence for widespread anoxia during the late Rhaetian in the Tethys ocean,
an emergence of widespread photic zone euxinia was documented right before and across the
Triassic/Jurassic boundary in the Tethys realm (Richoz et al., 2012; Hilebrand et al., 2013; Jaraula
et al., 2013; Fujisaki et al., 2020). This evidence for episodic euxinic-anoxic conditions during the
late Rhaetian adds to the growing dataset that environmental conditions began to deteriorate
preceding the onset of CAMP volcanism.
Mean annual temperature increases between 7 and 9 ºC are documented from the Late
Norian to the Rhaetian Stage using oxygen and carbon isotope data of pedogenic carbonates from
the Western Interior of North America (Cleveland et al., 2008). These temperature increases are
associated with two extreme peaks in pCO2 (between 1500 and 3000 ppmV) levels across the
Rhaetian preceding the ETE (Cleveland et al., 2008). These significant changes in temperature
likely initiated extreme seasonal fluctuations and widespread heat stress (Cleveland et al., 2008)
possibly leading to the biotic crisis before the onset of the ETE.
5.4. Discussion
During the Norian Stage, the Tethys basin is characterized by a significant drop in generic
richness of 41% in contrast to increased diversity in the Panthalassa and Boreal basins. Observed
trends in Tethys perhaps could be related to documented arid climate in the region and pervasive
dolomitization affecting the health of marine ecosystems via changing ocean chemistry (Berra et
al., 2010; Berra, 2012; Berra and Angiolini, 2014). The multiple carbon cycle perturbations at the
end of the Norian significantly impacted marine invertebrates across all basins. When the
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Rhaetian-Norian transition is compared to the Rhaetian-Hettangian transition either in generic
richness percentage across the basins or across taxa, the decline in generic richness was more
severe during the Norian-Rhaetian transition (Fig. 4) suggesting that marine invertebrates were
already declining preceding the end-Triassic mass extinction (Tanner et al., 2004; Kiessling et al.,
2007; Lucas and Tanner, 2018; Rigo et al., 2020). Previous studies (Hallam, 2002; Tanner al.,
2004) recognized an elevated extinction across the NRB, thus questioning the ETE as a true mass
extinction event. Kiessling et al. (2007) ran the analysis of Sepkoski’s compendium (Sepkoski,
2002) and pointed out the extinction rates were above background from the Carnian to the
Rhaetian. Yet, when the end-Triassic extinction rates are compared to a Middle Triassic to Middle
Jurassic background, it stands out as a true mass extinction event (Kiessling et al., 2007). The
Rhaetian elevated extinction signal is complicated by strongly reduced origination rates (Bambach
et al., 2004) and a shorter stage duration when compared to the Norian and Carnian (Bambach et
al., 2004; Kiessling et al., 2007). Kiessling et al. (2007)’s study acknowledged the gradual
biodiversity decline across Norian-Rhaetian and into the Rhaetian-Hettangian stage boundaries.
When functional diversity of all organisms is analyzed during the Rhaetian, meaningful
fluctuations in functional diversity have not been observed (Dunhill et al., 2017).
The restructuring of ecological systems in the aftermath of the ETE caused a delay of two
million years before returning to pre-extinction ecological conditions (Ritterbush et al., 2014). In
Eastern Panthalassa, as the ecosystem started slowly to recover above the Triassic/Jurassic
boundary, siliceous sponges spread across a midshelf habitat, in a "sponge takeover", for the
following two million years (Ritterbush et al., 2014; Corsetti et al., 2015) and didn’t fully recover
until the Sinemurian Stage. Panthalassa was the only basin for which this coarse time frame data
shows a decline in marine invertebrate biodiversity from the Rhaetian to the Hettangian (Fig. 4A),
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possibly as a result of (1) precursor environmental perturbations, episodic anoxic to euxinic
conditions, that reduced ecosystem stability before the onset of the ETE and (2) the post extinction
“sponge takeover” phenomenon that caused prolonged recovery. In addition, difference in faunal
and geochemical trends between Tethys and Panthalassa could be partially attributed to ocean
circulation patterns, basin size, diverse climate patterns, oxygenation events, and weathering
profile.
5.5. Conclusions
• Major turnover of cephalopods happened during the Norian-Rhaetian transition, largely at
the Norian-Rhaetian boundary (Fig. 4B) (Lucas and Tanner, 2018; Rigo et al., 2020).
However, cephalopods almost became extinct at the ETE when their generic richness was
already impoverished.
• The extinction of marine invertebrates on a stage-by-stage basis during the Late Triassic
shows the lowest documented generic richness during the Rhaetian Stage, implying a
significant role for the transition between the Norian and Rhaetian on marine invertebrates
across the globe (Fig. 4). Yet, additional studies of this transition are required to fully
resolve the causes and consequences of this major reduction in biodiversity since the
Rhaetian stage is complicated by lower orgination rate and a shorter duration compared to
the Norian and Carnian Stage.
• During the end-Triassic mass extinction, marine fauna inhabiting the Panthalassic basin
was more affected compared to the Tethys basin likely due to the detrimental impact of
pre-extinction episodic euxinic to anoxic conditions and the post-extinction “sponge
takeover” phenomenon.
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• Despite increased generic richness across all the basins during the Sinemurian, marine
invertebrates never reached the level of generic richness documented either during the
Norian or Sinemurian Stages.
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Figures Chapter 5
Figure 1. Schematic diagram of faunal and carbon perturbation events occurred during Late
Triassic along with a simplified organic carbon isotope curve. Modified after Rigo et al., 2020
and DalCorso et al., 2020.
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Figure 2. Reconstruction of Late Triassic globe showing the occurrence and distribution of
Animalia. The diagram is derived from the Paleobiology Database. The panel on the right shows
the most abundant taxa present during the Late Triassic including Carnian, Norian and Rhaetian
Stage.
Late Triassic
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Figure 3. Paleoreconstruction of the Late Triassic globe showing fossil occurrences used in this
study across Boreal, Panthalassic, and Tethys basins. Adapted from Dunhill et al. 2017.
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Figure 4. Marine inverterbrates diversity across basins (A) and across taxa (B) during Late
Triassic to Lower Jurassic.
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239
Figure 5. Generic richness of marine invertebrates (Brachiopoda, Bivalvia, Cephalopoda, and
Gastropoda) from Carnian to Sinemurian Stage A) across all basins, B) across Panthalassa basin;
C) across Tethys basin; D) across Boreal basin.
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Figure 6. Marine invertebrate generic occurrences across basins (A) and across taxa (B) during
Late Triassic to Lower Jurassic.
0
100
200
300
400
500
600
700
Carnian Norian Rhaetian Hettangian Sinemurian
Generic richness
Across Basins
Globe Panthalassa Tethys Boreal
A
0
50
100
150
200
250
Carnian Norian Rhaetian Hettangian Sinemurian
Generic richness
Across Taxa
Brachiopoda Bivalvia Cephalopoda Gastropoda
B
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239
226
239
Figure 7. Generic occurrences of marine invertebrates (Brachiopoda, Bivalvia, Cephalopoda,
and Gastropoda) from Carnian to Sinemurian Stage A) across all basins, B) across Panthalassa
basin; C) across Tethys basin; D) across Boreal basin.
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CHAPTER 6. CONCLUSIONS
The results of this work demonstrate that the pre-extinction conditions were complex and
varied spatially and temporally between the basins leading up to the ETE. Significant
biogeochemical changes occurred before the onset of the main phase of CAMP volcanic activity
in the Panthalassa basin while palaeoecological and paleoenvironmental conditions in the Tethys
indicate a steady state scenario followed by a sudden biotic collapse coinciding with the carbon
cycle perturbation event (or the initial negative carbon isotope excursion) initiated by the main
phase of CAMP volcanism. New details on the marine extinction mode and tempo coupled with
high resolution geochemical and petrographic analyses are documented for the first time. This
research highlights the importance of studying the precursor events on the regional and global
scale for an accurate reconstruction of chronology and spatial distribution of mechanisms that
acted during the lead up to the major biotic crisis.
Evidence of episodic deoxygenation events during the Late Rhaetian was documented at
two distant locations deposited in different parts of the Panthalassa basin. At the Ferguson Hill
site, Nevada, the timing of suboxic conditions coincides with the “precursor” carbon cycle
perturbation event and the first appearance of chemosymbiotic lucinids and low oxygen tolerant
taxa illustrating a substantial impact of biogeochemical changes on the benthic community in
Eastern Panthalassa (Chapter 2). At Williston Lake, British Columbia, evidence for fluctuating
euxinic-anoxic conditions is based on the deposition of upper Rhaetian phoshorite beds. This
research implies the expansion of the Oxygen Minimum Zone (OMZ) into shallow water settings
of the foreland basin in northeastern Panthalassa for the first time (Chapter 3).
In the Tethys realm, this study documents the presence of a robust marine benthic
community across different parts of the basin with an ecologically diverse and trophically complex
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benthic community in the shallower part of the basin right before the onset of the ETE (Chapter
4). Using an integrated framework encompassing data from this study combined with the published
literature (e.g., Ruhl et al., 2009, 2010, 2011; Bonis et al., 2010; McRoberts et al., 2012;
Hillebrandt et al., 2013; Pálfy et al., 2021) we propose that the amalgamation of environmental
conditions such as reduced salinity, episodic anoxia/hypoxia and ocean acidification caused a
sudden ecological crisis in the Tethys basin (Chapter 4). Despite disparities in paleoenvironmental
and paleoecological trends in the lead up to the ETE across the basins, the severity of the extinction
is apparent across the globe once the main phase of CAMP volcanic activity was initiated.
The effects of the end-Triassic mass extinction on marine fauna were more evident in the
Panthalassic Ocean compared to the Tethys and Boreal Oceans (Dunhill et al., 2017). I propose
that precursor perturbations of the carbon cycle overlapped by episodic suboxic conditions in the
Panthalassa Ocean created a hostile environment for marine faunas resulting in an elevated
extinction rate and a protracted recovery in Panthalassa (Chapter 5).
Future studies
This thesis highlights the importance of high-resolution studies using integrative analysis
of geochemical, sedimentological and faunal datasets. Specifically, the precursor carbon cycle
perturbation event and its impact on terrestrial and marine biota should be investigated further via
high-resolution sampling of every 20 cm or lower at different sites across the globe. Future studies
are required to resolve the relationships between the precursor deoxygenated event in the Williston
Lake region and its effect on shallow water benthic metazoans. Will restructuring of the marine
benthic community, if any, at Williston Lake be parallel to the observed faunal distribution at the
Ferguson Hill site?
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The putative temporal correlation of documented biogeochemical and biotic changes
during the pre-extinction interval with the early phase of CAMP emplacement is suggestive of
cause-and-effect relationships. Yet, a lack of absolute age dating of sediments and reliable proxies
for differentiating between CAMP intrusives and extrusives limits the understanding of triggering
mechanisms during the ETE.
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References
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239
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APPENDIX A. TABLES AND FIGURES FOR CHAPTER 2
Figure S1. Representative samples of thin sections under cathodoluminescent microscope
collected A. at 0.35m, Muller Canyon Member; B. at 1.1m, Muller Canyon Member; C. at -
1.2m, Mount Hyatt Member, D. at -0.3m, Mount Hyatt Member.
A
B
C D
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239
Figure S2. Stratigraphic section of the studied locality (Ferguson Hill, Nevada) with all
geochemical data (δ
13
Corg, TOC, δ
13
Ccarb, CaCO3, Hg, Hg/TOC). Ash bed at -3.75m remains
undated due to lack of suitable thickness for necessary sample acquisition.
δ
13
C
carb
‰
-1 1
CaCO
3
% %TOC
0.0 0.5 0 20 50
0.0 0.5 -1 1 0 20 50
δ
13
C
org
‰
-30 -28
-30 -28
m.
1
0
-1
-2
-3
-5
-4
Volcanic Ash
-6
Mount Hyatt Member Muller Canyon
ETE Pre-extinction interval
0 100
Hg/TOC [Hg] ppb
0 50
0 100 0 50
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239
Table S1. Geochemical data on all samples. NA = not analysed; R = replicate; TOC = total organic
carbon.
Horizon
(m.)
δ
13
C org(‰) TOC(%) δ
13
C carb(‰) CaCO 3 (%) Hg
(p.p.b.)
Hg/TOC
-6.55
-27.51 0.15 -1.55 22 21.1 136.7
-6.55 R
-27.51 NA NA NA NA NA
-6.25
-27.90 0.24 -1.13 7 10.4 43.6
-6.25 R
-27.92 NA NA NA NA NA
-5.95
-27.26 0.15 NA NA 12.6 86.8
-5.95 R
-27.20 NA NA NA NA NA
-5.7
-27.97 0.15 0.57 22 12.6 81.4
-5.4
-28.89 0.16 -0.76 29 3.9 24.6
-5.1
-28.60 0.20 -0.80 13 4.6 22.8
-4.8
-28.30 0.12 0.81 64 4.0 33.3
-4.5
-27.46 0.08 1.23 64 3.3 41.8
-3.85
-28.15 0.11 0.58 50 5.5 49.9
-3.85 R
-28.30 NA NA NA NA NA
-3.5
-28.34 0.24 1.00 63 8.5 34.9
-3.35
-28.16 0.11 0.90 60 4.6 42.4
-3.35 R
-28.30 NA NA NA NA NA
-3.2
-28.67 0.24 0.08 46 10.7 44.2
-2.8
-28.57 0.19 0.89 62 18.8 100.2
-2.4
-29.07 0.23 0.70 55 14.8 64.0
-2.1
-28.38 0.33 NA NA 16.9 51.5
-2
-27.95 0.30 0.15 17 18.9 62.3
-1.9
-28.31 0.33 -0.11 19 22.3 67.8
-1.8
-28.48 0.31 -0.10 20 18.3 58.4
-1.7
-28.86 0.43 -0.23 19 16.8 39.5
-1.6
-28.72 0.35 -0.17 21 14.9 42.1
-1.5
-28.35 0.44 0.26 37 NA NA
-1.4
-28.26 0.17 0.72 52 12.2 73.2
-1.3
-28.55 0.38 0.25 40 NA NA
-1.2
-28.26 0.19 0.48 41 12.7 66.1
-1.1
-28.43 0.21 0.01 36 NA NA
-1
-28.68 0.16 0.74 65 8.1 51.9
-0.9
-28.20 0.24 0.00 39 NA NA
-0.9 R
-28.09 NA NA NA NA NA
-0.8
-28.46 0.31 0.22 5 48.7 158.2
-0.7
-28.57 0.35 0.07 25 NA NA
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239
-0.7 R
-28.45 NA NA NA NA NA
-0.6
-28.69 0.36 0.29 25 42.5 116.5
-0.5
-28.30 0.23 0.92 52 NA NA
-0.5 R
-28.04 NA NA NA NA NA
-0.4
-28.34 0.19 0.46 55 15.2 78.3
-0.35
-28.34 0.19 0.39 22 NA NA
-0.35 R
-28.35 NA NA NA NA NA
-0.33
-28.42 0.29 0.32 34 32.7 111.2
-0.3
-28.46 0.47 -0.03 3 NA NA
-0.3 R
-28.44 NA NA NA NA NA
-0.23
-28.45 0.25 -0.14 37 NA NA
-0.18
-28.46 0.31 0.20 29 22.8 73.6
-0.18 R
-28.44 NA NA NA NA NA
-0.12
-28.37 0.23 -0.43 48 NA NA
-0.12 R
-28.40 NA NA NA NA NA
-0.1
-28.28 0.22 -0.72 28 16.6 77.1
-0.03
-28.41 0.21 -0.40 17 NA NA
-0.05
-28.31 0.28 -1.01 21 NA NA
-0.05 R
-28.26 NA NA NA NA NA
0
-28.38 0.28 0.09 59 15.3 53.9
0 R
-28.41 NA NA NA NA NA
0.08
-28.41 0.17 0.10 59 15.2 89.1
0.08 R
-28.46 NA NA NA NA NA
0.15
-28.24 0.27 -0.15 51 NA NA
0.2
-28.21 0.30 -0.46 33 13.2 44.5
0.2 R
-28.18 NA NA NA NA NA
0.25
-28.41 0.27 -0.56 49 NA NA
0.3
-28.41 0.27 0.07 22 20.3 76.1
0.3 R
-28.44 NA NA NA NA NA
0.31
-28.59 0.26 -0.10 30 NA NA
0.31 R
-28.58 NA NA NA NA NA
0.35
-28.43 0.26 -0.43 23 NA NA
0.4
-28.41 0.21 0.02 43 14.7 71.4
0.45
-28.37 0.21 0.14 22 NA NA
0.49
-28.58 0.21 -0.72 35 NA NA
0.5
-28.50 0.24 -0.06 33 24.8 102.3
0.5 R
-28.50 NA NA NA NA NA
0.53
-28.55 0.25 -0.49 35 NA NA
0.53 R
-28.60 NA NA NA NA NA
0.6
-28.89 0.20 0.08 59 37.8 186.4
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239
0.68
-28.65 0.40 -0.64 16 32.3 80.5
0.68 R
-28.59 NA NA NA NA NA
0.8
-28.39 0.30 -0.27 8 26.8 90.8
0.8 R
-28.40 NA NA NA NA NA
0.9
-28.99 0.38 -0.74 16 33.7 88.7
1
-28.45 0.28 -0.14 11 35.6 126.4
1.1
-30.25 0.38 -0.15 8 39.1 101.9
1.2
-30.00 0.34 0.33 6 52.7 155.6
1.3
-29.52 0.26 -0.19 10 46.7 181.3
1.3 R
-29.39 NA NA NA NA NA
1.35
-29.61 0.24 -0.17 10 40.8 169.0
1.5
NA NA -0.37 9 26.5 NA
1.6
-28.96 0.16 -0.41 9 25.3 160.8
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239
Table S2. Point-count data from microfacies analysis for all samples.
Figure
horizon (m.)
Bioclasts Clastic grains Fe-stained
cement
Goethite
(%)
Ca-
Cement
Other
-6.55 0 33 13 1 37 16
-6.45 0 35 9 2 20 35
-6.35 0 26 6 6 60 13
-6.25 2 30 4 2 16 46
-6.15 0 4 3 1 92 0
-5.95 0 24 5 6 15 50
-5.85 0 23 9 15 28 25
-5.7 1 37 2 12 36 12
-5.6 2 10 2 12 74 1
-5.5 0 30 7 11 22 30
-5.4 0 26 11 2 49 10
-5.3 0 20 7 7 62 4
-5.2 0 12 12 6 65 5
-5.1 0 35 11 2 18 34
-5 0 40 21 2 32 5
-4.9 1 45 14 1 37 2
-4.8 2 18 9 1 70 1
-4.7 5 18 15 0 61 1
-4.6 1 4 11 3 81 0
-4.5 4 5 12 1 78 0
-3.85 3 11 15 1 70 1
-3.5 5 5 8 1 88 0
-3.4 3 10 7 1 79 0
-3.35 4 19 12 0 65 0
-3.3 0 31 11 6 44 8
-3.2 0 16 15 0 69 0
-3.1 0 38 15 2 28 14
-3 0 34 22 4 31 4
-2.9 0 9 12 4 68 0
-2.8 1 10 8 4 75 0
-2.7 0 8 8 1 79 0
-2.5 1 38 39 0 22 0
-2.4 4 29 6 4 57 0
-2.3 2 20 15 3 59 0
-2.2 0 46 20 0 34 0
-2.1 1 45 25 0 29 0
238
239
-2 0 40 18 1 41 0
-1.9 0 59 20 0 21 0
-1.8 0 46 17 12 27 0
-1.7 0 49 26 1 24 0
-1.6 0 32 32 0 31 0
-1.5 2 24 16 5 53 0
-1.4 0 16 9 10 58 0
-1.3 2 26 11 3 58 0
-1.2 31 11 24 3 32 0
-1.1 0 27 15 4 54 0
-1 19 5 27 2 46 0
-0.9 1 10 9 16 62 2
-0.8 10 39 31 3 16 0
-0.7 1 16 8 25 31 19
-0.6 15 14 17 10 44 5
-0.5 2 4 13 7 69 5
-0.4 4 3 10 7 75 1
-0.3 1 16 14 14 55 0
-0.18 0 10 3 8 76 0
-0.1 0 20 6 15 49 11
0 0 15 0 8 72 4
0.08 1 9 17 5 69 0
0.2 0 11 7 6 72 1
0.3 0 12 5 16 64 3
0.4 0 5 4 15 73 0
0.5 2 3 5 17 70 1
0.6 1 3 12 21 61 1
0.68 0 19 7 13 50 11
0.8 0 33 5 20 25 17
0.9 0 44 12 8 31 5
1 0 51 6 12 29 2
1.1 0 58 10 12 20 0
1.2 0 47 11 23 15 4
1.3 0 66 10 11 10 3
1.35 0 51 3 24 21 1
1.5 0 50 18 8 22 2
1.6 0 55 9 14 22 0
239
Table S3. Absolute abundances of macrofossils collected in the field. Horizon* = bulk samples. Indet. = indetermined.
Horizon
(m.)
Astarte sp.
Atreta sp.
Chlamys sp.
Malletiidae sp.
Mesomiltha sp.
Nuculoma sp.
Rhaetavicula sp.
Septocardia sp.
Species A
Species B
Bivalvia
indet.
Arcestes
gigantogaleatus
Arcestes sp.
Atractites sp.
Choristoceras
crickmayi
Choristoceras sp.
Nautiloidea
indet.
Ammonoidea
indet.
1.1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.85 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
0.7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
0.6* 4 0 9 0 1 6 0 0 0 0 7 0 0 0 0 3 0 0
0.5 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
0.4 0 0 1 1 0 1 0 0 0 0 3 0 0 0 0 0 0 0
0.3 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0
0.3 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.25 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
-0.2 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-0.25 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-0.45 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
-0.5 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
-0.8 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 1 0 0
-0.9 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-1 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0
-1.2* 1 0 1 0 1 19 0 1 0 0 18 1 1 5 0 0 1 0
239
239
-1.25 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0
-1.45 0 0 1 0 0 1 0 4 0 0 0 0 0 0 0 0 0 0
-1.5* 5 2 27 3 1 20 3 4 2 0 25 0 0 1 0 0 1 1
-1.6 0 0 2 0 0 5 0 0 0 0 4 0 0 0 0 0 0 0
-1.8* 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 1 0 0
-2.2* 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0
-2.45 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
-2.7 0 0 0 1 0 3 0 1 0 0 0 0 0 0 0 0 0 0
-2.8 0 0 1 0 0 0 5 0 0 0 0 0 0 0 0 0 0 0
-2.9* 0 0 9 0 1 14 3 10 0 1 14 0 1 1 0 0 0 0
-3.55 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
-4.65* 0 0 7 0 0 0 0 5 0 0 8 0 0 0 0 1 0 0
-5* 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
-5.15* 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-5.4* 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-5.8* 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-6* 0 0 2 0 0 2 0 0 0 1 3 0 0 1 0 1 0 0
240
241
239
APPENDIX B. TABLES AND FIGURES FOR CHAPTER 3.
Figure S1. Stratigraphic column of studied localities at Williston Lake, Canada. The absence and
presence of macro- and micro- fossils in thin sections are plotted next to each stratigraphic
column including echinoderms (= echin.) in green, molluscs (= mollsc.) in blue, brachiopods (=
brach.) in red, microfossils (=micro. ) and unidentifiable bioclasts (= biocla.).
15
18
10
5
0
Rhaetian
m.
?
10
5
0
m.
Pardonet Creek
Rhaetian Hett.
Ne Parle Pas
Norian
Purple fl ourite
Aragonite fan
Phos. ooids
Concretions Monotis bed
Absent
Present
Legend
Black Bear Ridge
0
4
Echin.
Molls.
Brach.
Micro.
Biocla.
Echin.
Molls.
Brach.
Micro.
Biocla.
Echin.
Molls.
Brach.
Micro.
Biocla.
Table S1. Description of thin sections analysed from the sites at Williston Lake, British Columbia.
Locaiton Formation Age Horizon (m.) Lithology
Fauna
(Presence/Absence)
Description
Pardonet
Creek
Pardonet
Formation
Norian -0.4 calcareous siltstone Bivalves Monotis sp. lots of pieces of
Monotis in cross-
section;
heavily Fe-
stained;
framboids are
present;
crinkly
laminations
Pardonet
Creek
Pardonet
Formation
lower
Rhaetian
0.5 calcareous siltstone radiolarians Heavily Fe-
stained;
some muscovite;
framboids are
present;
laminated
Pardonet
Creek
Pardonet
Formation
lower
Rhaetian
1.5 calcareous siltstone very rare pieces of
unidentifiable
shell fragments;
Heavily Fe-
stained;
silt (quartz and
mica);
goethite is
present.
242
239
Pardonet
Creek
Pardonet
Formation
lower
Rhaetian
2.6 packstone
cemented with
peloids and
bioclasts within the
hardground.
Hardground has
borings filled with
organics
very fossileferous -
most of shells are
filled with spar;
articulated bivalves;
radiolarians;
ammonitella;
echinoderms
fragments, lots of
ostracodes;
foraminifera
quartz and
muscovite
Pardonet
Creek
Pardonet
Formation
Rhaetian 3 calcareous siltstone unfossiliferous moderate Fe-
staining;
some framboids
Pardonet
Creek
Pardonet
Formation
Rhaetian 4 calcareous siltstone unfossiliferous moderate Fe-
staining;
dominated by
quartz
Pardonet
Creek
Pardonet
Formation
Rhaetian 5 calcareous siltstone unfossiliferous moderate Fe-
staining;
Pardonet
Creek
Pardonet
Formation
Rhaetian 5.5 calcareous siltstone phosphatized
ostracods and
pieces of shells. Lots of
broken pieces of
unknown shells.
Bivalve, molluscs shell;
echinoderms,
brachiopod fragments
some goethite
framboids;
lots of quartz and
phosphatic
grains;
heavily
phosphatised
243
239
Pardonet
Creek
Pardonet
Formation
Rhaetian 7 grainstone bivalves; few bivalves
filled
with silt and peloids
(frank said they were
ripped off from
different
environments and
brought there;
molluscan frags
phosphatic ooids
with calcite
crystals, shells as
nucleus;
spar matrix;
barely any Fe-
staining
Pardonet
Creek
Pardonet
Formation
Rhaetian 7.3-7.4 calcareous
siltstone/
grainstone
one whole valve of
bivalve;
echinoderm
sparse
phosphatic
grains;
quartz silt is
common;
muscovite is
present;
medium Fe-
staining;
lost of spar;
few goethite
framboids
Pardonet
Creek
Pardonet
Formation
Rhaetian 8.5 sandy grainstone
(because of spar
cement) with
phosphatic ooids
very few unknown
broken shell
fragments; mainly
unfossiliferous
phosphatic ooids;
silt as a nucleus
Pardonet
Creek
Pardonet
Formation
Rhaetian 9 sandy grainstone
(because of spar
cement) with few
phosphatic ooids
mold of a bivalve filled
with
pesoidal oraganic
matter-
medium Fe-
stained;
few phosphatic
ooids;
matrix:spar; silt
244
239
similar to #56; the rest
is unfossilierous
Pardonet
Creek
Pardonet
Formation
Rhaetian 9.65 silty phosphatic
oolitic grainstone
very rare shell
fragments
medium Fe-
stained
Pardonet
Creek
Pardonet
Formation
upper
Rhaetian
10 silty phosphatic
oolitic grainstone
extremmely rare shell
fragments
medium to high
Fe-staining;
lots of quartz silt;
Pardonet
Creek
Pardonet
Formation
upper
Rhaetian
10.2 silty phosphatic
oolitic grainstone
with silty matrix
unfossiliferous
Pardonet
Creek
Pardonet
Formation
T/J
boundary
10.3 looks like reworked
horizon;
broken pieces of
phosphatic
grainstone
embedded in
siltstone matrix;
sediment is
extremely dark-
could be full of
organics
unfossiliferous
245
239
Pardonet
Creek
Fernie
Formation
lower
Hettangian
11 laminated siltstone unfossiliferous quartz silt;
some muscovite;
rich in organics
Pardonet
Creek
Fernie
Formation
lower
Hettangian
12 siltstone unfossiliferous heavily Fe-
staining
Pardonet
Creek
Fernie
Formation
lower
Hettangian
13 calcareous siltstone unidentifiable small
shell fragments;
one brach fragment;
rather rare
laminated;
phophatic
rounded grains,
quartz silt;
goethite
framboids; Fe-
staining is
common
Pardonet
Creek
Fernie
Formation
lower
Hettangian
14(concretion) calcareous siltstone practically
unfossiliferous
but found one tiny
shell frag
very dark; either
lots of organic or
heavy Fe-staining
Pardonet
Creek
Fernie
Formation
lower
Hettangian
14 (around
concretion)
calcareous siltstone unfossiliferous
Pardonet
Creek
Fernie
Formation
lower
Hettangian
14.7 calcareous siltstone mainly unfossiliferous
iwith one brach
fragment
goethite
framboids,
Fe-staining
Pardonet
Creek
Fernie
Formation
lower
Hettangian
19 dark siltstone unfossiliferous very dark
coloration, could
be either lots of
organics or
heavy Fe-staining
246
239
Pardonet
Creek
Fernie
Formation
lower
Hettangian
19.5 super black smth;
quartz silt is rare
can see some
organisms in form of
small
rounds and see some
radiolarians that look
like bryozoans
Heavy Fe-
staining;
goethite
framboids
Pardonet
Creek
Fernie
Formation
lower
Hettangian
21 calcareous or
regular siltstone - it
is hard to tell
because extremely
dark
unfossiliferous laminated;
very dark
coloration, could
be either lots of
organics or
heavy Fe-staining
Ne Parle Pas Pardonet
Formation
Norian -0.5 siltstone ? Only Monotis sp. 0.5 m below the
top of Monotis
bed =
Norian/Rhaetian
boundary
Ne Parle Pas Pardonet
Formation
lower
Rhaetian
0.5 black siltstone extremely rare shell
pieces of
unidentifiable
bioclasts, some are
probably bivalves
Ne Parle Pas Pardonet
Formation
Rhaetian 1.5 black laminated
siltstone
extremely rare shell
pieces of
unidentifiable
bioclasts
Ne Parle Pas Pardonet
Formation
Rhaetian 2.5 black laminated
siltstone
one piece of molluscan
shell;
overall unfossiliferous
247
239
Ne Parle Pas Pardonet
Formation
Rhaetian 3.5 black calcareous
siltstone
extremely rare shell
pieces of
unidentifiable
bioclasts
Ne Parle Pas Pardonet
Formation
Rhaetian 4.5 black siltstone extremely rare shell
pieces of
unidentifiable
bioclasts
Ne Parle Pas Pardonet
Formation
Rhaetian 5.5 black siltstone bivalve fragment; very
rare bioclasts
Ne Parle Pas Pardonet
Formation
Rhaetian 6.5 black siltstone unfossiliferous
Ne Parle Pas Pardonet
Formation
Rhaetian 7.5 calcareous siltstone unfossiliferous lots of phosphatic
grains;
phosphatic ooids;
lots of Fe-staining
Ne Parle Pas Pardonet
Formation
Rhaetian 8.2 calcareous siltstone one small gastropod,
one piece of bivalve
shell; the rest is
unfossiliferous
phosphatic
grains;
phpsphatic vener
layer
Ne Parle Pas Pardonet
Formation
Rhaetian 9 calcareous siltstone unfossiliferous fe-staining;
goethite
framboids
Ne Parle Pas Pardonet
Formation
Rhaetian 9.7 calcareous siltstone unfossiliferous phosphatic ooids;
phosphatic clasts
248
239
Ne Parle Pas Pardonet
Formation
Rhaetian 10 black calcareous
siltstone
two parts:
1)unfossilifereous
black
calcareous siltstone 2)
phosphatic oolitic
grainstone with
various bivalve shells
two parts:
1)unfossilifereous
black
calcareous
siltstone 2)
phosphatic oolitic
grainstone with
various bivalve
shells
Ne Parle Pas Pardonet
Formation
Rhaetian 10.15 Upper layer: black
calcerous siltstone.
Lower layer:
phosphatic oolitic
grainstone.
Boundary is
gradational
upper layer:
unfossiliferous;
lower layer: lots of
bivalves, possibly one
bryaozoan bioclast
Ne Parle Pas Pardonet
Formation
Rhaetian 10.65 peloidal grainstone echinoderm and
molluscan fragments;
bryozoan
Ne Parle Pas Pardonet
Formation
Rhaetian 10.8 oolitic grainstone
with mm scale
stripes of siltstone
with rip ups of
bivalve with
irregular boundary.
Normal sorting
bivalves and other
unknown bioclasts
Ne Parle Pas Pardonet
Formation
Rhaetian 11 black laminated
siltstone
rare unkown bioclasts;
249
239
Ne Parle Pas Pardonet
Formation
Rhaetian 11.05 packestone with
broken shells, some
phosphatic ooids
and peloids
molluscan fragments;
echinoderm
fragments;
bivalve fragments
Ne Parle Pas Pardonet
Formation
Rhaetian 12 calcareous siltstone bivalves fragments
Ne Parle Pas Pardonet
Formation
Rhaetian 15 calcareous siltstone unfossiliferous with
very few
unidentifiable
bioclasts
Ne Parle Pas Pardonet
Formation
Rhaetian 15.5 calcareous siltstone
(not a lot of quartz
silt) with angular
phosphatic grains
unfossiliferous
Ne Parle Pas Pardonet
Formation
Rhaetian 16 calcareous siltstone
with phosphatic
grains and borings
filled with organics
mainly unfossiliferous;
one recrystallized
bivalve shell
ichtyosaur bed
Ne Parle Pas Pardonet
Formation
Rhaetian 17.15-17.4 calcareous siltstone
with some
phosphatic grains,
peloids
bivalve and brach
frags; poorly
fossiliferous
goethite
framboids
Ne Parle Pas Pardonet
Formation
Rhaetian 17.5 oolitic grainistone very few
unidentifiable
bioclasts
Ne Parle Pas Pardonet
Formation
Rhaetian 18 calcareous siltstone unfossiliferous goethite
framboids
Black Bear
Ridge
Pardonet
Formation
Norian-
Rhaetian
-0.5 shale bivalve fragments 250
239
Black Bear
Ridge
Pardonet
Formation?
Norian-
Rhaetian
0 laminated shale;
possibly microbially
influenced
lamination
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
0.5 Greene's aragonite
layer
unfossiliferous
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
0.6 the entire thin
section is an
aragonite fan with
small cluster of
phosphatic ooids
unfossiliferous
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
0.7 Greene's aragonite
fan layer
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
1 siltstone bivalve fragments;
bioclasts are
moderately abundant
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
1.5 dark brown/blackish
siltstone
very rare bioclasts
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
2 dark brown
siltstone
unfossiliferous
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
2.5 dark brown
siltstone
mainly unfossiliferous;
extremely rare
bioclasts
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
3 siltstone unfossiliferous with
one bioclast
Black Bear
Ridge
Fernie
Formation
lower
Hettangian
3.7 calcareous siltstone
tofine-grained
sandstone
unfossiliferous Fe-staining;
goethite
framboids
251
239
Pardonet
Creek
Pardonet
Formation
lower
Rhaetian
0 fine grained
sandstone
mainly
unfossiliferousvery
few bivalves
252
253
239
Figure S2. Energy Dispersive Spectroscopic analysis of the sample from Black Bear Ridge at 0
m.
Data Type: Net Counts
Image Resolution: 512 by 340
Image Pixel Size: 1.53 µm
Map Resolution: 512 by 340
Map Pixel Size: 1.53 µm
Acc. Voltage: 15.0 kV
Magnification: 350
254
239
255
239
256
239
Figure S3. Energy Dispersive Spectroscopic analysis of the sample from Pardonet Creek at 7 m.
Data Type: Counts
Image Resolution: 512 by 340
Image Pixel Size: 1.53 µm
Map Resolution: 512 by 340
Map Pixel Size: 1.53 µm
Acc. Voltage: 10.0 kV
Magnification: 350
257
239
258
239
239
APPENDIX C. TABLES AND FIGURES FOR CHAPTER 4.
Table S1. Description of thin sections analysed from the Restentalgraben site, Austria
Member Thin
section
label
Depth
(m.)
Macrofacies Matrix
M-micrite,
S-
microsparite,
B - bioclasts
Sp - sparite
Grains (amount) Microfacie
s
Additional
Info
Eiberg RS1 0 Bioclastic packstone M, S, B -echinoderms (+++),
- brachiopods
-bivalves (+++)
- gastropods (+)
- corals (+)
MF4 - styolites
- sparite
veins
- shells
recrystalize
d in sparite
or filled
with micritic
matrix
- some
foliated and
prismatic
structure
- voids filled
with sparite
- geopetal
pore space
- silt-size
quartz
grains
259
239
- peloidal
matrix
- mix of
whole and
fragmented
shells
Eiberg RS53 -27.5 Grainstone B, M, S, Sp - bioclasts(+++)
- quartz silt (+++)
- bivalves (++)
-gastropods (+++)
- ooids (+++)
- brachiopods
- bioclasts in mud
clasts
- foram (++)
- echinoderms (+)
MF5 -stylolites
-bioclasts
and ooids
are
recrystallize
d filled with
micrite
cement
- sparite
veins
- mud clasts
- isopachous
cement
around
bioclasts
and ooids
- coated
grains,
shells and
pellets
-
260
239
Glomospira
sp. ?
Eiberg RS50 -26.3 mudstone M, S - bivalve (+)
- quartz silt (++)
MF1 - ii2
- sparite
vein
Eiberg RS45 -24.6 oolitic grainstone Sp - mudclasts (+++)
- ooids (+++)
- echinoderms (+++)
- gastropods (+)
– coral (+)
- foram (+)
- sponge spicule
- bivalve (+)
MF5 - grains are
enveloped
in micrite
-
phosphatize
d grains
Eiberg RS39 -22.5 rudstone with fg
packstone
Sp - echinoderms (+++)
- bivalves (+++)
- brachiopods (+++)
- gastropods (++)
- forams (++)
- ostracods (+)
MF4 -rudstone
separated
by fine-
grained
packstone
-
Glomospira
sp. ;
261
239
Eiberg RS34 -20.5 mudstone (marl) M, S no shells MF2 - laminated
- ii1
- no silt
- very little
of sparite,
mostly
micrite
Eiberg RS13 -5.3 mudstone M, S no shells
–ghost structures (++)
MF1 - ii3
- sparite
veins
- very fg
mudstone
with
possibly
burrow
filled with
coarser
grained
more silica
rich
sediment
(quartz silt)
Eiberg RST31C -6.4 bioclastic rudstone M, S - bivalves (+++)
- brachiopods (++)
- echinoderms (++)
- quartz silt (+)
MF4 -
recrystallize
d shells
- sparite
veins
-
preferential
orientation
of bioclasts
262
239
Eiberg RS22 -9.8 silty mudstone (marl) M - quartz silt (+++)
- no shells
MF2 - numerous
sparite
veins
Eiberg RS19 -9.5 silty mudstone (msrl) M, S - bioclasts (+)
- quartz silt (+++)
MF2 - little
amount of
tiny
bioclasts
-
bioturbated
ii3
Eiberg RS17 -8 bioclastic packstone M, S - echinoderms (+++)
- foram (++)
- brachiopods (++)
- bivalves (+++)
- bryozoans (++)
- tabulate coral (+)
- sponge (+)
MF4 -
bioturbated
ii4
- weird
matrix
texture
- stylolites
-
recrystallize
d bioclasts
- unsorted
- the most
diverse TS
- nodosaria
sp?;
aulotortus
sp.(Flugel)
263
239
Eiberg RS16B -7.5 bioclastic packstone M, S - quartz silt (+++)
- echinoderms (+++)
- bivalves (+++)
- bryozoans (++)
- rounded mud clasts
- corals (+)
– foram (+)
MF4 - main
component
is
echinoderm
fragments
– half of
bioclasts are
recrystallize
d
- mud clasts
are present,
rounded
- nodosariid
RS16T -7 Bioclastic packstone M, S, B - echinoderms (+++)
- bivalves (+++)
- brachiopods (+++)
- rounded mud clasts
(+++)
– serpulid (+)
- gastropod (++)
- sponge (+)
- ammonite
- coral (+)
- bryozoans (++)
MF4 - heavily
recrystallize
d and
broken
down
– sparite
veins
- shells filled
with dark
matrix (for
ex., sponge
and gastro)
- were
exposed to
more
diagenesis
compared
to 16B
264
239
because of
sparite
matrix in
parts and
broken
material
Eiberg RS14 -6 wackestone M, S - ghost structures
(shells filled with
micrite)
- gastro (+)
- bivalves (++)
MF3 - fg micrite
with minot
microsparit
e
- stylolites
- mainly tiny
bioclasts <
0.5 mm
- ii3
265
239
Eiberg RS6 -2.5 bioclastic rudstone M, S - echinoderm
- bivalves (+++)
MF4 - all shells
are
recrystallize
d
- two layers:
one has less
shells and
higher silt
content,
another is
packed with
shells and fg
micrite
matrix --
typical
tempestite
layer
266
239
Eiberg RS5 -2.2 mudstone M, S - bivalve (+)
- echinoderm (+)
MF1 laminated
partially
- rare shell
fragments -
usually
whole valve
- sparite
veins
- divided
into three
parts:
laminated
mudstone,
mudstone
(scour like
feature)
with
bioturbated
mudstone
which is
more rich in
silica and
bioclasts are
more
abundant at
the base
267
239
Eiberg RS4 bioclastic wackstone
with packstone on the
top
M, S wackstone:
-ostracods (++)
- echinoids (++)
- bivalves (+++)
- gastropods (+)
- brachipods (++)
packstone:
- gastropods
echinoids (+++)
- bivalves (+++)
- gastropods (+)
- brachipods (++)
MF3 - ii4
- most shells
are
recrystallize
d with
sparite
- sparite
veins
268
239
Table S2. Description of thin sections analysed from the Eiberg site, Austria.
Formati
on
Memb
er
Unit Thin
section
label
Depth
(m.)
Macrofacies Matrix
M-micrite,
S-
microspari
te
Grains Micro
-facies
Additional Info
Kossen
Fm
Eiberg Unit
2
M 17.9 laminated
mudstone
M, S -echinoderm (+)
-unknown shell
clasts (+)
-
mictosparite(+)
- foram? (+)
MF1 - numerous sparite
veins with
interesting
microstructures
(some wavy and
resembling
molluscan shells)
-ghost shell
structures (rare)
- broken clasts
-one distinct V-
shaped burrow -
Zoophycos? show
to Aly)
-clay rich
-barely any
microsparite
Kossen
Fm
Eiberg Unit
4
Bed 17 62.5 mudstone M, S -recrystallized
shell
clasts (+)
-echinoderm (+)
-microsparite
(+)
MF1 -numerous sparite
veins
-ghost shell
structures
- all shells are
broken
- bioturbated (can
see Planolites)
-barely any
microsparite
269
239
Kossen
Fm
Eiberg Unit
3
Bb8 39.5 mudstone M, S -microsparite
(+++)
MF1 -rare sparite veins
(less than in
previous sections)
-very rare ghost
shell fragments
(fragments are tiny)
- practically fossil
free
- bioturbated
Kossen
Fm
Eiberg Unit
2
B 2 mudstone/marl M, S -microsparite
(+++)
MF2 - bioturbated
- ocassionaltiny
shell fragments less
0.4mm
mainly <0.2mm
-very rare
molluscan shell
fragments of 4 mm
-numerous sparite
veins
Kossen
Fm
Eiberg Unit
2
E2 9.4 mudstone M, S -microsparite
(+)
MF1 -bioturbated with
one distinct burrow
- ghost shell
structure (rare)
-rare tiny shell
fragments <1mm
-calcite veins
-barely any
microsparite
270
239
Kossen
Fm
Eiberg Unit
4
Bed 36 mudstone M, S -microsparite
(+)
-ostracode(++)?
-mollusc (+)
MF1 - bioturbated (i3)
- ocassionaltiny
shell fragments
between 0.2 and
0.5mm
-very rare
molluscan and more
J11abundant
ostracode shell
fragments
-numerous sparite
veins
-barely any
microsparite
Kossen
Fm
Eiberg Unit
4
Bed 23 mudstone M, S - microsparite
(+)
-ostracode (+)?
-molluscs(+)
MF1 - well-bioturbated
- ghost shell
structure (common)
-rare tiny shell
fragments <1mm
-calcite veins
-barely any
microsparite
271
239
Kossen
Fm
Eiberg Unit
3
Bb9 47 mudstone M, S -molluscs (+)
-microsparite
(++)
- annelid?
MF1 - slightly
bioturbate…laminat
ions are visible
-few calcite veins
-ghost shells
-mostly tiny shell
fragments - mostly
unidentifiable due
recrystallization
Kossen
Fm
Eiberg Unit
4
30 cm
below
bitumino
us
layer
30 cm
below
bitumino
us
layer
mudstone M, S -microsparite
(+)
ghost bioclasts
(+)
MF1 - tiny ghost and not
ghost bioclasts
- bioclasts are very
rare < 0.5 m
- sparite veins are
common
- not bioturbated
but laminations are
not prominent
either
Kossen
Fm
Eiberg Unit
2
C 4.5 mudstone M, S -microsparite
(+)
-bioclasts (++)
-echinoderm
(++)
- bivalves (+)
MF1 -numerous sparite
veins
- shell fragments <
0.5mm are common
- lightly bioturbated
272
239
Kossen
Fm
Eiberg Unit
4
Bed 20 61.2 mudstone M, S -microsparite
(+)
-bioclasts (+)
-echinoderm (+)
- bivalves (+)
MF1 - bioturbated (i3)
- ocassionaltiny
shell fragments
between 0.2 and
0.5mm
-very rare bioclasts
-some sparite veins
-barely any
microsparite
- ghost structures
are common
Kossen
Fm
Eiberg Unit
4
Bed 10 mudstone M, S -microsparite
(+)
- ghost
structures (++)
- bivalves
bioclasts (+)
MF1 -- homogeneous …
no visible
bioturbations
- abundant gshost
structures
- rare bioclasts
-sparite veins (++)
Kossen
Fm
Eiberg Unit
4
Bed 31 57 dark brown mudstone M, S -microsparite
(+)
-bioclasts(++)
-bivalve(++)
MF1 - laminated
-bioclasts are large
compared to
previous shells >2
mm in most cases
- no sparite veins
- some ghost
structures
273
239
Kossen
Fm
Eiberg Unit
2
Top E 10 mudstone M, S -microsparite
(+)
-bioclasts (+)
-ghost
structures (++)
MF1 -bioturbated (ii4)
-fine-grained
-ghost structure are
common
- shell fragments
are tiny <0.2 mm
with the exception
of one large shell
(few mm)
- one sparite vein
Kossen
Fm
Eiberg Unit
4
Bb10a 53.5 mudstone M, S -microsparite
(++)
-bioclasts(+)
- ghost
structures (+++)
-echinoderm (+)
-molluscs (+)
MF1 - few sparite veins
-bioturbation is not
visible (ii2)
Kossen
Fm
Eiberg Unit
4
Bed 27 58.2 wackestone M, S - bivalve (+++)
- ostracod(++)
-gastropod (+)
-echinoderm (+)
- ghost
structures (+++)
MF3 - numerous sparite
veins
- wackestone with
packestone filled
burrows
274
239
Kossen
Fm
Eiberg Unit
2
Bb5 27 ls mudstone M, S -bivalves (++)
-ostracod (+)
-bioclasts(++)
-
echinoderms(+)
- ghost
structures (++)
MF1 -ghost structures
are common
- bioturbated (ii4)
- sparite veins
- bioclasts are
replaced with
sparite
Kossen
Fm
Eiberg Unit
2
EB296 19.5 wackestone M, S -echinoderm
(++)
- brachiopods
(+)
-bivalves (++)
- sparite (+++)
MF3 -sparite veins
-bioclasts are large
compared to all thin
sections above up
to 2 cm
-bioturbated (ii4)
Kossen
Fm
Eiberg Unit
4
Z mudstone M, S - sparite (+++)
- ghost
structures (++)
- echinoderms
(+)
-bivalve (+)
MF1 - sparite veins (+++)
- tiny bioclasts <0.5
mm
Kossen
Fm
Eiberg Unit
2
D1 8.1 mudstone M, S -sparite (+++)
-
echinoderms(++
)
-bioclasts(++)
-ghost
structures (+)
-foram(++)
-ostracods(+)
MF1
275
239
Kossen
Fm
Eiberg Unit
2
D 7.1 mudstone M, S -ostracods (++)
- molluscs (+)
- bioclasts (+)
MF1 -bioturbated (ii4)
-ghost structure are
common
- shell fragments
are tiny <0.3 mm
with the exception
of one large shell
(few mm)
- sparite veins (++)
Kossen
Fm
Eiberg Unit
2
EB189 5 dark brown mudstone M, S -ostracods (+)
- molluscs (+)
- bioclasts (+)
MF1 -organic rich
- bioturbation (ii2)
- very rare bioclasts
- one broken
articulated
brachiopod
- sparite veins (+)
Kossen
Fm
Eiberg Unit
3
Bb8b 42 mudstone M, S - bivalves (++)
- echinoderms
(++)
- ostracods (+)
MF1 - bioturbated (ii3 to
ii4)
- ghost structures
(++)
- bioclasts are rare
and very small
<0.3mm
- sparite veins
Kossen
Fm
Eiberg Unit
2
C2 6.2 dark brown
mudstone/marl
M, S - bivalves (+)
- echinoderms
(+)
MF1/M
F2
- bioturbated (ii2 to
ii3)
- bioclasts are very
rare - practically
couple of
echinoderm and
bivalve fragments
276
239
Kossen
Fm
Eiberg Unit
4
Bed 40 dark brown mudstone M, S - bioclasts (+)
- ostracod? (+)
MF1 - bioturbated (ii2)
mostly laminated
- bioclasts are very
rare <0.4 mm
Kossen
Fm
Eiberg Unit
4
Bed 4 mudstone M, S - bioclasts (+)
- ostracod? (+)
MF1 - very fine-grained
- Planalites
- bioturnbation (ii4)
- sparite veins
- very rare bioclasts
present <0.3mm
- ghost structures
(+)
Kossen
Fm
Eiberg Unit
4
Bed 14 63.1 fine-grained
wackestone
M, S - bivalve (+++)
- ostracod(++)
- ghost
structures (+++)
MF1 - numerous calcite
veins
- ghost structure
(+++)
- bioturbated (ii4)
- bioclasts are tiny
<0.4mm
Kossen
Fm
Eiberg Unit
2
Bb3b 20.5 dark brown
wackestone
M, S -bivalve (+++)
-echinoderms
(++)
- foram(+)
MF3 - ii2 lamination is
visible
- bioclasts are more
common and larger
than in D3
Kossen
Fm
Eiberg Unit
3
Bb9a 48.5 mudstone
to wackestone
M, S -brachiopod (+)
- bioclasts (+++)
- bivalves (+)
- echinoderm
(+)
- ostracod (+)
MF3 - ii2 lamination is
visible
- lots of bioclasts
that are hard to ID
277
239
Kossen
Fm
Eiberg Unit
3
Bb10 50 mudstone to
wackestone
M, S -bioclasts (++)
- gastropod (+)
- bivalves (++)
- ammonoid (+)
- echinoderm
(+)
MF3 - ii3 to ii4
278
239
Table S3. Description of thin sections analysed from the Juifen site, Austria.
Formation Member Unit Thin
section
label
Depth (m.) Macrofacies Matrix
M-micrite,
S-
microsparite
Grains Microfacies Additional Info
Kossen Fm Eiberg Unit 4 T bed 10.1 organic rich
bioclastic
wacke-to
packstone
M, S - bioclasts (+++)
- echinoderms
(+)
- bivalves (+++)
MF3 - shell material
is highly
fragmented
- bioclasts are
poorly sorted
and large >1mm
- mostly
laminated with
shelly layers
- sparite veins
- ii2
Kossen Fm Eiberg Unit 4 Bed 14 7.25 wackestone M, S -ghost
structures (+++)
- echinoderms
(+)
- bivalves (++)
- brachiopod
(+)
MF3 - matrix is made
of sparite,
micrite and
tiny bioclasts
(=<0.1mm)
-ii4
- numerous
sparite veins
279
239
Kossen Fm Eiberg Unit 4 Bed 14b 7 wackestone M, S - echinoderms
(+)
- bivalves (++)
- brachiopods
(+)
- ostracods (+)
MF3 - matrix is made
of sparite,
micrite and
tiny bioclasts
(=<0.1mm)
-ii4
- numerous
sparite veins
- stylolites
Kossen Fm Eiberg Unit 4 Bed 16 6.3 wackestone M, S - echinoderms
(+)
- bivalves (++)
- ghost
structures (+++)
MF3 - sparite veins
-ii4
Kossen Fm Eiberg Unit 4 Bed 22 4.5 packstone M, S -echinoderms
(++)
-bivalves (+++)
-brachiopods
MF3 -stylolytes
-sparite veins
-ii4
Kossen Fm Eiberg Unit 4 Bed 25 2 packstone M, S - echinoderms
(+++)
-bivalves (++)
-brachiopods
MF3 -sparite veins
-ii4
Kossen Fm Eiberg Unit 4 Bed 33 1 packstone M, S - echinoderms
(+++)
-bivalves (++)
-brachiopods
(++)
MF3 - ii3 to ii4
- sparite veins
-large shell
fragments
280
239
Kossen Fm Eiberg Unit 4 Bed 39 0.1 packstone M, S - echinoderms
(+++)
-bivalves (+++)
-brachiopods
(++)
MF3 -stytolytes
281
239
Table S4. Description of thin sections analysed from the Kuhjoch site, Austria.
Formation Member Unit Thin
section
label
Depth
(m.)
Macrofacies Matrix
M-micrite,
S-
microsparite,
B - bioclasts
Sp - sparite
Grains Micro-
facies
Additional Info
Kossen Eiberg Unit 4 #15 -5 laminated marl M, clay (silver
stuff)
- goethite framboids +++
- quartz silt ++
MF2 - reddish golden
hue
- one possible
ostracod
Kossen Eiberg Unit 4 #16 -4.3 mudstone (ls) M, clay (silver
stuff)
- goethite framboids +++
- foraminifera +
- bivalve +
MF1 - reddish golden
hue
- small
concentraion of
shells incl. one
foram and an
ostracod shell
- rare shells that
are present are
recrystallized or
filled with
micrite
- nodosariid
Propesci 2010
282
239
Kossen Eiberg Unit 4 #17 -3.99 wackestone to
packstone
M, S - brachiopods +++
- echinoderms ++
- bivalves +
- ostracods ++
- foram ++
MF3 - ghost
structures are
common
- shells are
recrystallized
and filled with
sparite;
- shells are
mainly whole
but with one
valve;
Kossen Eiberg Unit 4 #18 -3.8 to
-3.78
fine-grained
wackestone
to pc
-quartz silt +++
- bioclasts ++
- goethite framboids +++
- foram +
- ostracods +
MF3 - tiny bioclasts.
some are filled
with goethites
- nodosariid
foram
Kossen Eiberg Unit 4 #19 -3.23
to -
3.19
wackestone
to packstone
M, S - bioclasts +++
- ostracods ++
- echinoderms +
- foram +
- brachiopod clasts +
- mollusc clasts +
MF3 - similar to #17
- tiny bioclasts,
mainly
recrystallized
and filled with
sparite;
- ghost
structures are
common
- calcite veins
Kossen Eiberg Unit 4 #20 -2.86
to -
2.92
wackestone
to packstone
M, S - foraminifera +
- echinoderms +
- bioclasts +++
- brachiopods +
MF3 - tiny bioclasts;
- ghost
bioclasts;
283
239
Kossen Eiberg Unit 4 #21 -2.44
to -
2.46
layer 1:
laminated marl
layer 2:
wackestone
M, S marl:
-echinoderms ++
- bioclasts ++
- goethite framboids +++
- foram +
wackestone:
- echinoderms ++
- bioclasts +++
MF3 wackestone:
- tiny bioclasts;
- ghost
bioclasts;
- lots of
bioclasts are
recrystallized
- unknown
foram
Kossen Eiberg Unit 4 #22 -1.88
to -
1.93
wackestone to
bioclastic fine
grained
packstone
M, S - ostracods ++
- ammonoid +
- echinoderms +
- foram ++
MF3 - bioturbated
ii4;
- ghost
structures;
- tiny bioclasts
which are
mainly
recrystallized
and filled with
sparite
Kossen Eiberg Unit 4 #23 -1.76
to -
1.81
marly bioclastic
fine-grained
wackestone
M, S - foraminifera ++
- echinoderms ++
- bioclasts +++
- brachiopods ++
- bivalves ++
- ammonoid +
MF3 - tiny bioclasts
which are
mainly
recrystallized
and filled with
sparite;
- calcite veins
Kossen Eiberg Unit 4 #24 -1.02
to -
0.94
fine-grained
wackestone
M, S - ostracods ++
- echinoderms +
- brachiopod +
MF3 less fossiliferous
than #22 and
#23
- tiny bioclasts;
- calcite veins;
284
239
Kossen Eiberg Unit 4 #25 -0.5 to
-0.54
fine-grained
wackestone
M, S - ostracods +++
- foraminifera +
- bivalves ++
- brachiopods +
- echinoderms +
MF3 differs from
sample 24 in
terms of higher
number of
ghost
structures;
- ghost
structures are
predominant;
- recrystallized
bioclasts
- identifiable
bioclasts are
rare
Kossen Eiberg Unit 4 #26 -0.2 to
-0.25
marly fine-
grained
wackestone to
mudstone
M - foraminifera +
- bioclasts ++
- echinoderms ++
- ostracods ++
MF3 - calcite veins
- tiny bioclasts
- stylolites;
- mollusc shells
but clasts are so
tiny, hard to ID
Kendelbach Tiefengra
ben
T bed #27 -0.13 organic-rich,
bioclastic, fine-
grained
wacke- to
packstone
M, S - foraminifera ++
- bioclasts +++
- echinoderms +++
- ostracods ++
- gastropod +
- brachiopod clast +
- quartz silt ++
MF3 - calcite veins
- tiny bioclasts
- mollusc shells
but clasts are so
tiny, hard to ID
- punctate
brachipod shell
- echinoderm
plate with
reticulate
structure
(Popescu 2010)
285
239
Kendelbach Tiefengra
ben
T bed #28 -0.04
to -
0.08
fine-laminated,
bioclastic, fine-
grained
wackestone to
packstone
M, S - foraminifera ++
- bivalve +++
- echinoderms +++
- goethite framboids +++
- brachiopods +
- bioclasts +++
MF3 - lots of tiny
bioclasts,
similar size
(aound 0.2-0.5
mm)
- dark brown
coating
- foliated
bivalve shell
- hard to ID
because
bioclasts are
heavily
fragmented and
are tiny
- nodosariid
foram
Kendelbach Tiefengra
ben
betw
een
bitum
inous
bed
and
Schat
twald
beds
#29 0 to
0.1
marly
mudstone
M, clay,
quarts silt
- quartz silt +++
- goethite framboids +++
MF2 - golden hue
Kendelbach Tiefengra
ben
betw
een
bitum
inous
bed
and
Schat
twald
beds
#30 0.25 to
0.3
marly
mudstone
M, clay,
quarts silt
- quartz silt +++
- goethite framboids +++
MF2 -golden hue
286
239
Kossen Eiberg Unit 4 #31 --0.1 to
-0.17
marly fine-
grained
wackestone to
mudstone
M - foraminifera +++
-echinoderm+
- brachiopod +
-bivalve +
- ostracods ++
MF3 - calcite veins
- foliated
bivalve shell
- laminated in
places
Kendelbach Tiefengra
ben
T bed #32 -0.05
to 0
fine-laminated,
bioclastic, fine-
grained
wackestone to
packstone
M, S - foraminifera ++
- echinoderms +
- bioclasts +++
MF3 - lots of tiny
bioclasts,
similar size
(aound 0.2-0.5
mm)
- dark brown
coating
- hard to ID
because
bioclasts are
heavily
fragmented and
are tiny
- goethite clasts
- calcite veins
Kendelbach Tiefengra
ben
bitum
inous
layer
#33 0 marly mudstone M, silvery ash - goethite framboids +++
- quartz silt +++
MF2 - reddish golden
hue
- silvery matrix
Kendelbach Tiefengra
ben
Schat
twald
beds
#34 0.3 to
0.35
marly
mudstone?
M, clay (silver
stuff)
-quartz silt +++ MF2 - reddish golden
hue
- silvery ash
- lenses of
quartz silt with
silvery stuff as
matrix
287
239
- partially
laminated
Kendelbach Tiefengra
ben
Schat
twald
beds
#35 0.92 to
0.97
marly
mudstone?
M, clay (silver
stuff)
- quartz silt +++ MF2 - reddish golden
hue
- silvery ash
- lenses of
quartz silt with
silvery stuff as
matrix
- partially
laminated
Kendelbach Tiefengra
ben
Schat
twald
beds
#36 1.4 to
1.45
marly
mudstone?
M, clay (silver
stuff)
-quartz silt +++ MF2 - reddish golden
hue
- silvery ash
- lenses of
quartz silt with
silvery stuff as
matrix
- partially
laminated
Kendelbach
Tiefengra
ben
Schat
twald
beds #37
1.5 to
1.55
marly
mudstone?
M, clay (silver
stuff)
-quartz silt +++ MF2 - reddish golden
hue
- silvery ash
- lenses of
quartz silt with
silvery stuff as
matrix
- partially
laminated
288
239
Kendelbach Tiefengra
ben
Schat
twald
beds
#38 can
exlude
this
sample
marly
mudstone?
M, clay (silver
stuff)
-quartz silt ++ MF2 - reddish golden
hue
- less quartz
than in the
samples above
- likely
laminated, but
because it is like
clay and we
collected it
under the rain,
so it became
like lump
Kendelbach
Tiefengra
ben
Schat
twald
beds #39 2.2
marly
mudstone?
M, clay (silver
stuff)
- quartz +
MF2 - reddish golden
hue
- homogeneous
matrix
- almost no
quartz
Kendelbach
Tiefengra
ben
Tiefe
ngrab
en
marls #40 2.45
marly
mudstone?
M, clay (silver
stuff)
- goethite framboids +++
- quartz silt ++
MF2 - reddish golden
hue
- silvery matrix
Kendelbach Tiefengra
ben
Tiefe
ngrab
en
marls
#41 3.45 marly
mudstone?
M, clay (silver
stuff)
-goethite framboids +++
- quartz silt +++
MF2 - reddish golden
hue
- silvery matrix
- dark layer in
the center with
light lenses
- possible
burrow
Kendelbach
Tiefengra
ben
Tiefe
ngrab
en
marls #42 4
marly
mudstone?
M, clay (silver
stuff)
- goethite framboids +++
- quartz silt +++ MF2
- reddish golden
hue
- silvery matrix
289
239
Kendelbach Tiefengra
ben
Tiefe
ngrab
en
marls
#43 5.1 marly mudstone M, clay (silver
stuff)
- goethite framboids +++
- quartz silt +++
MF2 - reddish golden
hue
- silvery matrix
Kendelbach Tiefengra
ben
Tiefe
ngrab
en
marls
#44 5.7 marly mudstone M, S - goethite framboids +++
- quartz silt ++
- echinoderms +
- bioclasts +
MF2 - one
echinoderm
fragment
- fine-grained
micrite
Kendelbach Tiefengra
ben
#45 6.05 to
6.1
marly mudstone M, S -goethite framboids +++
- quartz silt +
- bioclasts +
MF2 - fine-grained
micrite
Kendelbach Tiefengra
ben
#46 6.65 to
6.6
marly mudstone M, S - goethite framboids +++
- bivalve +
- bioclasts ++
- quart silt +
MF2 - fine-grained
micrite
Kendelbach Tiefengra
ben
#47 7 marly mudstone M, S
- goethite framboids +++
- quartz silt +
- bioclasts
MF2
290
239
Table S5. Description of thin sections analysed from the Schlossengraben site, Austria.
Formation Member Unit Thin
section
label
Depth
(m.)
Macrofacies Matrix
M-micrite,
S-microsparite,
B - bioclasts
Sp - sparite
Grains Micro-
facies
Additional Info
Kossen Eiberg Unit
4
#1 -2.14 fine-laminated
marl
M, S goethite
framboids
+++
MF2 almost mudstone;
lots of goethite framboids
Kossen Eiberg Unit
4
#2 -2 mudstone M, S ghost
structures
+++
bioclasts +
peloids +++
echinoder
m +
MF1 - fractures filled up with goethite
framboids
- some wackestone on a side with
bioturbated boundary
- tiny bioclasts
Kossen Eiberg Unit
4
#3 -1.8 to -
1.9
laminated
marly wc to pc
M, S peloids +++
foram +
bioclasts
+++
echinoder
ms ++
gpethite
framboids
+++
brachiopod
s ++
radiolarian
s +
MF3 - shell of impunctate and
punctate brachs
- dominated by small bioclasts
that are hard to ID
291
239
Kossen Eiberg Unit
4
#4 -0.99 to -
1.08
fine-grained
wc to pc
M, S - sparite
veins +++
- bioclasts
+++
-
echinoder
ms ++
-
brachiopod
s +
- ostracods
+
MF3
- almost all bioclasts are
recrystallized
Kossen Eiberg Unit
4
#5 -0.65 to -
0.7
fine-grained
wc to pc
M, S - sparite
veins +++
- bioclasts
+++
-
echinoder
ms +
MF3 - almost all bioclsts are
recrystallized
Kossen Eiberg Unit
4
#6 -0.18 to -
0.24
fine-grained
wc to pc
M, S - sparite
veins +++
- bioclasts
+++
-
echinoder
ms +
-
foraminifer
a +
MF3 - styolites
Kendelbach Tiefengra
ben
T
bed
#7 -0.17 to -
0.12
fine-
laminated,
organic-rich,
bioclastic,
fine-grained
wacke-to
packstone
M, S -
echinoder
ms ++
- peloids
+++
- goethite
framboids
+++
- fine-
MF3 layer of goethite framboids
shark tooth
292
239
grained
bioclasts++
+
- bivalve +
Kendelbach Tiefengra
ben
T
bed
#8 -0.12 to -
0.08
fine-
laminated,
bioclastic,
fine-grained
wackestone
M, S -
echinoder
ms ++
- peloids
+++
- goethite
framboids
+++
- fine-
grained
bioclasts
+++
- foram +
- brachs ++
- ostracod
frags +
- bivalve +
MF3 -lots of goethite framboids
-impunct and punct brachiopods
- lots of tiny bioclasts, similar size
(aound 0.2-0.5 mm)
Kendelbach Tiefengra
ben
T
bed/
bito
min
ous
layer
#9 -0.03 to 0 fine-
laminated,
organic rich,
fine-grained
bioclastic,
bituminous
rich
M, S, silvery stuff
(ash?)
-
echinoder
ms ++
- goethite
framboids
+++
- fine-
grained
bioclasts
+++
- bivalve ++
-
brachiopod
- lots of tiny bioclasts, similar size
(aound 0.2-0.5 mm)
- dark brown coating
- two layers: 1. typical T bed as
below but has a brown coating;
2. silvery layer (bituminous layer)
where even bioclasts are
replaced with silvery stuff,
probably ash
293
239
s +
- foram +
- ostracods
+
Kendelbach Tiefengra
ben
Bitu
min
ous
later
#10 0 to 0.05 marly
mudstone
M, clay, quarts
silt, ash?
- quartz silt
+++
- goethite
framboids
+++
- bioclasts
+
MF2 silvery veins like in the sample #9
- reddish golden hue
- occassional tiny bioclasts, very
rare, hard to ID
Kendelbach Tiefengra
ben
Scha
ttwa
ld
beds
#11 0.4 to
0.45
marly
mudstone
M, clay, quarts
silt, ash?
- quartz silt
+++
- goethite
framboids
+++
- bioclasts
+
MF2 silvery veins like in the sample
#10, but more rare
- reddish golden hue
- found just couple of shells,
probably ostracods
Kendelbach Tiefengra
ben
Scha
ttwa
ld
beds
#12 1 to 1.05 marly
mudstone
M, S, - quartz silt
+++
- goethite
framboids
+++
MF2 -reddish golden hue
Kendelbach Tiefengra
ben
Scha
ttwa
ld
beds
#13 1.4 to
1.45
red mudstone
/marl
- calcite
veins
MF2 brecciated
294
239
Kendelbach Tiefengra
ben
Scha
ttwa
ld
beds
#14
1.6 to
1.65
red/goldish
mudstone/marl
- calcite
veins MF2
red layer and golden layer
brecciated
295
239
Table S6. Mode of life of fauna collected in the Northern Calcareous Alps, Austria.
Species Name Phylum Class Order Family Tiering Motility Feeding Mineralogy
Agerchlamys
textoria Mollusca Bivalvia Pectinida Pectinidae epifaunal
facultatively
mobile suspension feeding
low Mg calcite,
aragonite
Atreta
intusstriata Mollusca Bivalvia Pectinida Dimyidae epifaunal stationary suspension feeding
low Mg calcite,
aragonite
Cassianella
inaequiradiata
Mollusca Bivalvia Ostreida Cassianellidae epifaunal stationary suspension feeding
low Mg calcite,
aragonite
Chlamys
valoniensis Mollusca Bivalvia Pectinida Pectinidae epifaunal
facultatively
mobile suspension feeding
low Mg calcite,
aragonite
Chlamys favrii
Mollusca Bivalvia Pectinida Pectinidae epifaunal
facultatively
mobile suspension feeding
low Mg calcite,
aragonite
Chlamys sp. Mollusca Bivalvia Pectinida Pectinidae epifaunal
facultatively
mobile suspension feeding
low Mg calcite,
aragonite
Crinoids Echinoder
mata Crinoidea epifaunal stationary suspension feeding high Mg calcite
Entolium sp.
Mollusca Bivalvia Pectinida Pectinoidea epifaunal
facultatively
mobile suspension feeding
low Mg calcite,
aragonite
Fissirhynchia
fissicostata
Brachiopod
a
Rhynchonel
lata
Rhynchonel
lida
Cyclothyridida
e epifaunal stationary suspension feeding low Mg calcite
Gervillaria
inflata Mollusca Bivalvia Ostreida Bakevelliidae epifaunal stationary suspension feeding
low Mg calcite,
aragonite
Grammatodon
sp. Mollusca Bivalvia Arcida
Parallelodonti
dae epifaunal
facultatively
mobile suspension feeding aragonite
Meleagrinella
sp. Mollusca Bivalvia Pectinida Oxytomidae epifaunal stationary suspension feeding low Mg calcite
Oxycolpella
oxycolpos
Brachiopod
a
Rhynchonel
lata Athyridida
Diplospirellida
e epifaunal stationary suspension feeding low Mg calcite
Oxytoma
inequivalvis Mollusca Bivalvia Pectinida Oxytomidae epifaunal stationary suspension feeding low Mg calcite
Pecten sp.
Mollusca Bivalvia Pectinida Pectinidae epifaunal
facultatively
mobile suspension feeding
low Mg calcite,
aragonite
Placunopsis
alpina Mollusca Bivalvia Pectinida Plicatulidae epifaunal stationary suspension feeding
low Mg calcite,
aragonite
296
239
Placunopsis sp. Mollusca Bivalvia Pectinida Plicatulidae epifaunal stationary suspension feeding
low Mg calcite,
aragonite
Pseudolima cf.
hettangiensis
Mollusca Bivalvia Pectinida Limidae epifaunal stationary suspension feeding
low Mg calcite,
aragonite
Rhaetavicula
concorta Mollusca Bivalvia Ostreida Rhaetavicula epifaunal stationary suspension feeding
low Mg calcite,
aragonite
Rhaetavicula
sp. Mollusca Bivalvia Ostreida Rhaetavicula epifaunal stationary suspension feeding
low Mg calcite,
aragonite
Rhaetina
pyriformis
Brachiopod
a
Rhynchonel
lata
Terebratuli
da
Angustothyridi
dae epifaunal stationary suspension feeding low Mg calcite
Rhaetina sp. Brachiopod
a
Rhynchonel
lata
Terebratuli
da
Angustothyridi
dae epifaunal stationary suspension feeding low Mg calcite
Rhynchonella
subrimosa
Brachiopod
a
Rhynchonel
lata
Rhynchonel
lida Rhynchonella epifaunal stationary suspension feeding low Mg calcite
Zeilleria
elliptica
Brachiopod
a
Rhynchonel
lata
Terebratuli
da Zeilleriidae epifaunal stationary suspension feeding low Mg calcite
Zugmayerella
koessenensis
Brachiopod
a
Rhynchonel
lata
Spiriferinid
a
Spondylospirid
ae epifaunal stationary suspension feeding low Mg calcite
Zugmayerella
sp.
Brachiopod
a
Rhynchonel
lata
Spiriferinid
a
Spondylospirid
ae epifaunal stationary suspension feeding low Mg calcite
Cardinia
hybrida Mollusca Bivalvia Carditida Cardiniidae infaunal
facultatively
mobile suspension feeding aragonite
Homomya sp.
Mollusca Bivalvia
Pholadomyi
da
Pholadomyida
e infaunal
facultatively
mobile suspension feeding aragonite
Isocyprina cf.
ewaldi Mollusca Bivalvia Cardiida Arcticidae infaunal
facultatively
mobile suspension feeding aragonite
Isocypryna sp.
Mollusca Bivalvia Cardiida Arcticidae infaunal
facultatively
mobile suspension feeding aragonite
Myophoriopis?
isoceles Mollusca Bivalvia Carditida
Myophoricardi
idae infaunal
facultatively
mobile suspension feeding aragonite
Nuculana
claviformis Mollusca Bivalvia Nuculanida Nuculanidae infaunal
facultatively
mobile
deposit, suspension
feeding aragonite
Nuculana sp. Mollusca Bivalvia Nuculanida Nuculanidae infaunal
facultatively
mobile
deposit, suspension
feeding aragonite
Nuculanida
Mollusca Bivalvia Nuculanida Nuculanidae infaunal
facultatively
mobile
deposit, suspension
feeding aragonite
297
239
Palaeocardita
sp. Mollusca Bivalvia Cardiida
Palaeocarditid
ae infaunal
facultatively
mobile suspension feeding aragonite
Palaeonuculana
sundaica Mollusca Bivalvia Nuculida Nuculidae infaunal
facultatively
mobile
deposit, suspension
feeding aragonite
Palaeonuculana
sp. Mollusca Bivalvia Nuculida Nuculidae infaunal
facultatively
mobile
deposit, suspension
feeding aragonite
"Permophorus"
elongatus Mollusca Bivalvia Cardiida Kalenteridae infaunal
facultatively
mobile suspension feeding aragonite
Protocardia
rhaetica Mollusca Bivalvia Cardiida Cardiidae infaunal
facultatively
mobile suspension feeding aragonite
Protocardia sp.
Mollusca Bivalvia Cardiida Cardiidae infaunal
facultatively
mobile suspension feeding aragonite
Pseudocorbula
ewaldi Mollusca Bivalvia Cardiida Arcticidae infaunal
facultatively
mobile suspension feeding aragonite
Pteromya sp. Mollusca Bivalvia Pholadida Ceratomyidae infaunal
facultatively
mobile suspension feeding aragonite
Schafhaeutlia
sp. Mollusca Bivalvia Lucinida Lucinidae infaunal
facultatively
mobile chemosymbiotic aragonite
Choristoceras
ammonnitiform
e Mollusca
Cephalopod
a Ceratitida
Choristocerati
dae nektonic actively mobile carnivore aragonite
Choristoceras
marshi Mollusca
Cephalopod
a Ceratitida
Choristocerati
dae nektonic actively mobile carnivore aragonite
Choristoceras
sp. Mollusca
Cephalopod
a Ceratitida
Choristocerati
dae nektonic actively mobile carnivore aragonite
Inoperna
schafhaeutli Mollusca Bivalvia Mytilida Mytilidae
semi-
infaunal stationary suspension feeding
low Mg calcite,
aragonite
Inoperna
(Triasoperna)
schafhaeutli Mollusca Bivalvia Mytilida Mytilidae
semi-
infaunal stationary suspension feeding
low Mg calcite,
aragonite
Modiolus sp. Mollusca Bivalvia Mytilida Mytilidae
semi-
infaunal stationary suspension feeding
low Mg calcite,
aragonite
Pinna sp. Mollusca Bivalvia Ostreida Pinnidae
semi-
infaunal stationary suspension feeding
low Mg calcite,
aragonite
298
239
Table S7. Faunal distribution at Restentalgraben (= R), Juifen (= J) and Eiberg ( = E).
Locality
Bed Number
Agerchlamys textoria
Atreta intusstriata
Cardinia hybrida
Cassianella inaequiradiata
Chlamys valoniensis
Chlamys favrii
Chlamys sp.
Choristoceras ammonnitiforme
Choristoceras marshi
Choristoceras sp.
Entolium sp.
Fissirhynchia fissicostata
Gervillaria
inflata
Grammatodon sp.
Homomya sp.
Inoperna (Triasoperna) schafhaeutli
Isocyprina cf. ewaldi
Isocyprina sp.
Meleagrinella sp.
Modiolus sp.
Nuculana
claviformis
Nuculana sp.
Oxycolpella oxycolpos
Oxytoma inequivalvis
Palaeocardita sp.
Palaeonuculana sundaica
Palaeonuculana sp.
Pecten sp.
Pinna sp.
Placunopsis alpina
Placunopsis sp.
Protocardia
rhaetica
Protocardia sp.
Pseudocorbula
ewaldi
Pseudolima cf. hettangiensis
Pteromya sp.
Rhaetavicula concorta
Rhaetavicula sp.
Rhaetina pyriformis
Rhaetina sp.
Rhynchonella subrimosa
Schafhaeutlia sp.
Zeilleria elliptica
Zugmayerella koessenensis
Zugmayerella sp.
R
RS
Tbed
and
bit.
Laye
r 5 0
2
0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 2 0 0 0 2 0 0 0 0 0 0 3 0 0 0 1 0 0 0
R RS1 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
R RS4 0 1 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 0 0 0 0 0 0 3 1 0 0 0 1 0 0 0
R RS5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 2 3 1 0 0 0 1 0 0 0 0 0 4 1 1 0 2 0 0 0 0 0 0 0 0 0
R RS7 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
R RS14 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 4 0 0 2 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0
R
RS31
C 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0
R RS17 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
R RS19 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
R RS39 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
R RS42 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
R RS45 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
R RS53 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
J
T-
bed
and
bit.
layer 1 0 1 0 1 0 2 0 1 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
299
239
J
Bed
9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
J
Bed
14 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
J
Bed
22 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E
Bitu
mino
us
layer 1 0 2 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
9
0 0 0 0 0 0 0 0 0 0 0
E
~30
cm
belo
w
bit.
layer 0 0 1 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
E W 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0
E
Betw
een
Bb9
and
Bb10
=Bb9
/10 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E Bb9 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E U 0 0 0 0 0 0 3 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E Bb8b 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0
E Bb7b 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E
Bb7
=
EB30
7 0 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0
E Bb6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E S 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E Bb5 0 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E Bb3b 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E
O =
EB28
3 0 0 0 0 0 0 2 0 0 1 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 7 0 0 0 0 0 1
E H2 0 0 0 0 0 0 5 0 2 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E
Betw
een
E
and
F = 0 0 0 1 0 0 0 0 0 2 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
300
239
EB22
0
E
Top
E 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 1 3 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
E E2 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
E D2 0 0 0 0 0 2 2 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
E D1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E
C2
(bet
wee
n C
and
D) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
E
Belo
w C 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E
EB18
9
(bet
wee
n
C
and
B) 0 0 0 0 0 0 1 2 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E B 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
301
239
Table S7 (continued). Faunal distribution at Restentalgraben (= Rest.), Juifen and Eiberg.
Locality
Bed Number
Oxytoma inequivalvis
Palaeocardita sp.
Palaeonuculana sundaica
Palaeonuculana sp.
Pecten sp.
Pinna sp.
Placunopsis alpina
Placunopsis sp.
Protocardia
rhaetica
Protocardia sp.
Pseudocorbula
ewaldi
Pseudolima cf. hettangiensis
Pteromya sp.
Rhaetavicula concorta
Rhaetavicula sp.
Rhaetina pyriformis
Rhaetina sp.
Rhynchonella subrimosa
Schafhaeutlia sp.
Zeilleria elliptica
Zugmayerella koessenensis
Zugmayerella sp.
Rest.
RS Tbed and
bit. Layer 0 0 0 2 0 0 0 2 0 0 0 0 0 0 3 0 0 0 1 0 0 0
Rest. RS1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Rest. RS4 0 0 0 0 0 2 3 0 0 0 0 0 0 3 1 0 0 0 1 0 0 0
Rest. RS5 0 0 1 0 0 0 0 0 4 1 1 0 2 0 0 0 0 0 0 0 0 0
Rest. RS7 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Rest. RS14 0 0 0 4 0 0 2 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0
Rest. RS31C 0 0 0 0 0 0 3 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0
Rest. RS17 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Rest. RS19 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
Rest. RS39 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
Rest. RS42 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
Rest. RS45 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Rest. RS53 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Juifen
T-bed and bit.
layer 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
Juifen Bed 9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
Juifen Bed 14 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
302
239
Juifen Bed 22 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g
Bituminous
layer 0 0 0 0 0 0 0 0 0 0 0 90 0 0 0 0 0 0 0 0 0 0
Eiber
g
~30 cm below
bit. layer 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
Eiber
g W 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0
Eiber
g
Between Bb9
and
Bb10 =Bb9/10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g Bb9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g U 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g Bb8b 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0
Eiber
g Bb7b 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g Bb7 = EB307 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0
Eiber
g Bb6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g S 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g Bb5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g Bb3b 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g O = EB283 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 7 0 0 0 0 0 1
Eiber
g H2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g
Between E
and
F = EB220 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
303
239
Eiber
g Top E 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
Eiber
g E2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
Eiber
g D2 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g D1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g
C2 (between C
and D) 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g Below C 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g
EB189
(between
C and B) 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Eiber
g B 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
304
239
APPENDIX D. TABLES FOR CHAPTER 5.
Table S1. Generic richness of analyzed dataset from the PBDB.
Globe
Phylum
Number of raw generic
occurrences Carnian Norian Rhaetian Hettangian Sinemurian
Brachiopoda 220 123 119 52 35 58
Bivalvia 250 132 142 123 100 104
Cephalopoda 386 157 154 34 45 90
Gastropoda 304 202 100 54 46 55
All taxa 1160 614 515 263 226 307
Panthalassa
Phylum
Number of raw generic
occurrences Carnian Norian Rhaetian Hettangian Sinemurian
Brachiopoda 60 29 29 20 7 15
Bivalvia 167 66 89 46 48 90
Cephalopoda 241 98 102 21 30 42
Gastropoda 99 16 62 51 0 10
All taxa 468 193 220 87 85 147
Tethys
Phylum
Number of raw generic
occurrences Carnian Norian Rhaetian Hettangian Sinemurian
Brachiopoda 187 99 99 33 27 48
Bivalvia 182 99 87 97 69 46
Cephalopoda 253 100 88 20 26 70
Gastropoda 260 260 58 7 45 48
All taxa 882 558 332 157 167 212
305
239
Boreal
Phylum
Number of raw generic
occurrences Carnian Norian Rhaetian Hettangian Sinemurian
Brachiopoda 35 15 13 10 8 5
Bivalvia 64 10 36 12 31 22
Cephalopoda 53 31 12 1 8 6
Gastropoda 4 1 1 0 2 1
All taxa 156 57 62 23 49 34
306
Abstract (if available)
Abstract
The end-Triassic mass extinction (ETE) is one of the biggest biotic crises that has occurred during geological history and the main cause is generally attributed to the emplacement of the Central Atlantic Magmatic Province (CAMP) ~201.51 million years ago. The ETE was the most devastating extinction for the so-called Modern Fauna and the triggering mechanisms associated with the ETE, such as global warming, ocean acidification, ocean anoxia and sea-level changes, are analogous to imminent environmental perturbations. The amount of CO₂ injected into the atmosphere during each CAMP magmatic pulse rivals anthropogenic CO₂ emission projected for the 21st century. Although the ETE and its aftermath are well documented, the conditions leading up to the ETE remain poorly understood. Yet, most recent studies emphasize the complexity of the pre-extinction scenario and the importance of deciphering precursor events to the ETE if the mechanisms for this "Big 5" mass extinction are to be fully delineated. Elucidating the triggering mechanisms of past extinction events and their effects on Earth system behavior are particularly critical nowadays as we are entering the sixth mass extinction. ❧ This study aims to resolve environmental conditions in marine realm that acted in the lead-up to the ETE and its impact on the complexity of marine benthic ecosystems. Specifically, the precursor events during the late Triassic have been explored at different scales varying from micro- (microns to cms) to macro-scale (ms to kms) across different geographic areas. Two regional case studies of three sections from British Columbia and one from Nevada, USA, are presented to establish biogeochemical and biotic changes in Panthalassic realm. Biogeochemical and sedimentological analyses integrated with quantitative analysis of marine benthic community from the Panthalassic sections reveal episodic deoxygenated events and restructuring of marine benthic community towards more low oxygen tolerant taxa and lower diversity preceding the main phase of CAMP volcanism. At Ferguson Hill, Nevada, these changes closely follow the “precursor” negative carbon isotope excursion implying a truly global extent of the pre-extinction carbon cycle perturbation and highlighting the detrimental effect of fluctuations in carbon cycle on shallow marine ecosystems. In contrast, regional scale study of upper Rhaetian sections in Tethys realm reveals an ecologically diverse and robust marine benthic community across different depositional environments all the way up to the main phase of CAMP volcanism implying the sudden tempo of ecological changes in Tethys compared to the more protracted nature of ecological shifts recorded in the Panthalassa. Despite disparities in paleoenvironmental and paleoecological trends in the lead up to the ETE across the basins, the severity of the extinction is apparent across the globe once the main phase of CAMP volcanic activity was initiated. ❧ Using the Paleobiology Database and published literature, this study evaluated the extinction pattern of marine invertebrates on a stage-by-stage basis across different carbon cycle perturbation events during the Late Triassic. The quantitative analysis of marine invertebrates shows reduced generic richness in marine invertebrates across the basins implying an important role of the biotic turnover and carbon cycle perturbation event that happened at the Norian/Rhaetian boundary, however the biotic pattern is complicated by low origination rate and short duration of the Rhaetian stage. This work highlights the importance of pre-extinction studies at different temporal and spatial scales using integrative analysis of geochemical, sedimentological and faunal datasets.
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Larina, Ekaterina
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Core Title
Paleoenvironmental and paleoecological trends leading up to the end-Triassic mass extinction event
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College of Letters, Arts and Sciences
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Doctor of Philosophy
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Geological Sciences
Degree Conferral Date
2021-08
Publication Date
08/09/2021
Defense Date
06/05/2021
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carbon cycle,Central Atlantic magmatic province,end-Triassic mass extinction,episodic anoxia,OAI-PMH Harvest,precursor event
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Bottjer, David (
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carbon cycle
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end-Triassic mass extinction
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