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Paleoecology and depositional paleoenvironments of Pleistocene nearshore deposits, Las Animas, Baja California Sur, Mexico

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Paleoecology and depositional paleoenvironments of Pleistocene nearshore deposits, Las Animas, Baja California Sur, Mexico

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Content PALEOECOLOGY AND DEPOSITIONAL PALE012NV1R0NMEN IS OF PLEISTOCENE NEARSHORE DEPOSITS, LAS ANIMAS, BAJA CALIFORNIA SUR, MEXICO by Teresa Ann De Diego Forbis A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment o f the Requirements for the Degree .DOCTOR. OF PHILOSOPHY (GEOLOGICAL SCIENCES) December 2003 Copyright 2003 Teresa Ann De Diego Forbis Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3133258 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. ® UMI UMI Microform 3133258 Copyright 2004 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY O F SO U TH ERN CALIFORNIA TEE GRADUATE SCHOOL UNIVERSITY PARK LOS ANGELES, CALIFORNIA 900SM695 This dissertation, written by T e r e s a Ann Oe D i e g o F o r b i s under the direction o f h e r dissertation committee, and approved by all its members, has been presented to and accepted by the Director o f Graduate and Professional Programs, in partial fulfillment of the requirements far the degree of DOCTOR OF PHILOSOPHY Director Dissertation Committee i S , F i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DEDICATION I would like to dedicate this dissertation, to my husband, Kenny Edward Forbis, for having the patience to put up with ail o f my craziness for the past four years. You always believed 1 could do this and never put up with any o f my self-doubts. For all the late night crying, the self-pity whining, and the general grouching episodes, this one's for you sweetie. I would also like to dedicate this to my parents, Radi and Patricia De Diego, who always said I could do anything I put my mind to and believed it Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. M i ACKNOWLEDGEMENTS There are many people I would like to acknowledge for helping with this project. At the University o f Southern California I would like to thank my orals and dissertation committee members, Donn Gorsline, David Bottjer, Douglas Haimnand, and Gerald Bakus for their advice and contributions. I would especially like to thank my committee chair and advisor for the past seven years, Robert Douglas, who not only saw the potential in my research but also helped me to see it too. Also at U SC I would like to thank my k b mates Oscar Gonzales-Yajimovich, Francisca Staines- Urias, and Chanda Drennen for listening to my ideas and giving me sound advice. I would also like to thank Nicole Bonuso who came to my rescue with a great statistical program when 1 needed it. And lastly at USC, I would like to thank the Department o f Earth and its staff for their years o f mental, academic and financial, support. I would like to also thank the people at the Los Angeles County Museum of Natural History for advice and allowing me to use their modem molluscan collections. Thanks, Ken, Angel, and Leslie. A t the Centro Interdisciplinario de Ciencias Marinas - Institute Politecnio Nacional (CICMAR-IPN) I would like to thank Enrique Nava-Sanchez and his wife Janette Murillo-Jimenez for opening their home to me while I was in La Paz, Mexico, helping me with field work and sending me my samples when there were too many to take back to the lab in one trip. I would also like to thank all the people from CICIMAR-IPN, Raul, Gris, Patricia and Cesar, who willing went out into the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. tv more than 90< : , F field with me to help. Also, I would like to acknowledge Lucid Godfnez-Orta for allowing me to bring field samples back to United States. Lastly, 1 thank CICM A.R4PN for all its field support and use o f their vehicles. I also would like to thank the Department of Geological Sciences at the University o f Texas, Austin for their work on the U-series systematica. I would also like to thank my husband, Kenny Edward Forbis, for using his vacation to go out into the field with me and help. I wish to acknowledge funding from the U.S. National Science Foundation International Programs (U.S.-Mexico) (to R. Douglas and D. Gorsline), Conseja Nacional de Cienca y Tecnoiigta (CONACyT) (to E. Nava-Sanchez) and internal fending from, the University o f Southern California (to T. De Diego Forbis (graduate research, grant) and R, Douglas) for supporting this research. This project is part o f a joint University o f Southern California - Centro Interdiscipliimrio de Ctencias Marinas-Instituto Politecnico Nacional (CICMAR-IPN) research program on the sediments and paleoceanography o f the Gulf o f California. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V TABLE OF CONTENTS Dedication ii Acknowledgements iii List o f Tables ix List o f Figures x Abstract xtv Chapter 1 Introduction 1 Objective 7 Study Location 8 Geological Setting 13 Baja California Tectonics 13 Rancho Las Animas Regional Geology 15 Background 20 Modem Gulf o f California Nearshore Commtmltes 20 Corals Communities 24 El Pulmo 34 Puerto Escondido 35 Gulf Molluscan Communities 36 Rhodoliths 40 The Pleistocene G ulf 45 Pleistocene Climate 46 Substage 5e 46 Pleistocene Gulf Sea Level 48 Pleistocene Gulf Terraces 49 Cabo Pulmo 51 San Telmo 52 Punto Bajo 53 Chapter 2 54 M ethods 54 Field Methods 54 Sampling 54 Terrace Location and Elevations 54 Laboratory Methods 55 Fossil Identification 55 Cluster Methods 55 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. vi Age Dating 56 Grain. Sire Analyses 57 Chapter 3 58 Fossil Analyses 58 Fossil Identification 58 Terrace Litho- and Biofacies 58 Cerro Colorado Member 59 Basal Conglomerate Unit 59 Fossiliferous and Reworked Cerro Colorado Sand Unit 62 Large Coral Unit 62 Parties, Molluscan and Rhodolith Sandy Marls Unit 69 "Pencil" Parties and Molluscan Sandy Maris 70 "Finger" Porites, Molluscan and Rhodolith Sandy Marls 70 Rhodolith and Molluscan Marls 73 Fossiliferous Sands 75 Beach Gravels Unit 78 Oyster Beds and Mounds 78 Small Pocillopora 81 Rhodolith Mounds 81 Storm layers 86 Cluster Analyses 86 Introduction 86 Results 90 R-Mode Analyses 91 Q-Mode Analyses 95 Discussion 101 Chapter 4 104 Stratigraphy 104 Results 104 Localities Ani mas North 104 D2S9 104 D3S5 107 Local i ties Km 26 109 D6S8 109 D6S12 111 Locality Dune 111 D8S3 113 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. vii D12S6 113 Locality Road Cut 116 Discussion 118 Locality Animas North. 118 Locality Km. 26 123 Locality Dune 128 Comparison, o f Terrace Stratigraphy 131 Regional Area. Model 1.32 Typical. DepositionaJ Terrace Model 133 C hapters 135 Grain Size Analyses 135 Introduction 135 Results 137 Discussion 1.38 Locality Animas North 13 8 Comparison, o f Site D 1 . S 13 Samples 138 Comparison of Site D2S6 Samples 138 Comparison, o f Site D2S9 Samples 14 1 Comparison o f Site D3 S 5 Samples 14! Comparison o f Site D5S14 Samples 142 Locality Km. 26 142 Comparison o f Site D6S8 Samples 142 Locality Dune 143 Comparison o f Site D8S3 Samples 143 Other Localities 143 Road Cut 143 Across the Street from Road Pit 144 Grain Size Comparisons o f Facies 144 Fossiliferious and Reworked Cerro Colorado Sand Unit 144 Fossiliferous Sands 145 Subfacies Encope Sands 145 Large Coral Unit 146 Forties, Molluscan and Rhodolith Sandy Marls Unit 146 Subfacies "Pencil" Forties and Molluscan Sandy Marls 146 Subfacies Rhodoliths and Molluscan, Marls 147 Comparison of the Facies 147 Grain. Size Comparison o f the Terrace Segments 148 Locality Animas North 148 Locality Km 26 1.50 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. viii Locality Dune 150 Locality Road Cut 150 Comparison o f Terrace Localities ! 50 Chapter 6 152 Uraiiiuin~Seri.es Dating 152 Introduction 152 Results 153 Discussion 156 Chapter? 158 Tectonic Implications of the Terrace Segments 158 Introduction 158 Results and Discussion 159 Chapter 8 165 Rancho Las Animas Paleoenvironments 165 Comparison, o f Rancho Las Animas Pleistocene Deposits to Other Pleistocene Deposits 165 Comparison o f Pleistocene Deposits to Modern Gulf Fauna! Communities 166 Terrace Depositions! Paleoenvironment Model 172 Chapter 9 175 Conclusions 175 References 178 Appendix A. Latitudes and Longitudes o f Rancho Las Animas Sites 190 Appendix B. Las Animas Fossils 194 Appendix C. Las Animas Fossils' Distributions and Envi.ronm.ents 226 Appendix D. Stratigraphy o f Rancho Las Animas Pleistocene Deposits 234 Appendix E. Schematic Drawings o f Rancho Las Animas Terrace Segments 244 Appendix F. Las Animas Minute Moment Calculations 249 Appendix G. Rancho Las Animas Grain Size Frequency Graphs 278 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES Table 1. Grain Size Analyses. 139 Table 2. Isotopic Values and U-Series Ages for Corals. 155 Table 3. 'Uplift Rates o f Baja California Terraces. 160 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES Figure 1. Map o f Baja California with Close Up o f Terrace Locality. 3 Figure 2. Map o f Rancho Las Animas Terrace Segments. 5 Figure 3. Site Map for Animas North Terrace Segment 9 Figure 4. Map o f Terrace Segment Km 26 with Site Locations. 11 figure S. Map o f Dune Terrace Segment with Sites. 12 Figure 6. Stratigraphic column o f Tertiary Formations, El Cien and Comondu, lrom Outcrops Just South, o f Rancho .Las Animas. (Taken From Fischer et al. 1995). 16 Figure 7. Buff and Brown .Layers of Comondii Formation Seen in the Sierra Las Tarabillas in the Background. 18 Figure 8. Panoramic View South o f Terrace Dune Segment. Terrace Segment Km 26 Seen in the Background. This Photo Demonstrates the Terrace and Arroyo Topography. i 9 Figure 9. Modem Pocillopora sp. washed up on a Beach in El Coyote, 30 Figure 10. Photo o f Modern. Pocillopora elegans Coral heads near Isla EspirM, Baja California Sur, Mexico. 3 i Figure 11. Photo o f coral thickets near Isla Espiritu, Baja California Sur, Mexico. 32 Figure 12, Green Beds o f Cerro Colorado Member Overlain by the White Pleistocene Deposits at Animas North Terrace Segment. 60 Figure 13. Conglomerate Facies. Picture Taken at Site D4S2 in Animas North Terrace Segment 61 Figure 14. Fossiliferous and Reworked Cerro Colorado Member Sands. Picture Taken at Site D 1513 in Animas North Terrace Segment, 63 Figure 15. Large Corals Facies. Picture Taken at Site D6S12 in Km 26 Terrace Segment. 64 Figure 16. Platy Coral, Morphology Seen Growing Over Branching Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. X I Morphology. Picture Taken at Site D6S8 in Km 26 Terrace Segment. 66 Figure 17. Sandy Matrix o f Large Corals Seen W asted Away in Tains. Picture Taken at Site D2S9 in Animas North Terrace Segment. 67 Figure 18. “Pencil” Porites and Molluscan Sandy Marls Subfacies. Picture Taken at Site D12S6 in Dune Terrace Segment. 71 Figure 19. Porites, Molhiscan and Rhodolith Sandy Marls Facies, Picture Taken at Site D! S3 in Animas North Terrace Segment. 72 Figure 20. Rhodoliths and Molluscan Sandy Marls Subfaeies. Picture Taken at Site DSS11 in Animas North Terrace Segment. 74 Figure 21. Fossiliferous Sands Facies. Taken at Site D6S17 in Kin 26 Terrace Segment. 76 Figure 22. Encope Sands Subfacies. Picture Taken at Site D2S9 in Animas North Terrace Segment 77 Figure 23. Beach Gravel Facies. Picture Taken, at Site D9S7 in Dune Terrace Segment. 79 Figure 24. Oyster Bed Facies. 80 Figure 25. Oyster Mound at Site D2S4 in Animas North Terrace Segment. 82 Figure 26. Small Pocillopora Subfacies. Picture Taken at Site D8S3 in Dune Terrace Segment. 83 Figure 27. Arrow Pointing to Small Pocillopora Subfacies. Picture Taken at Site D3S5 in Animas North Terrace Segment. 84 Figure 28. Picture o f a Rhodolith Mound Taken at Site D1S9 in Animas North Terrace Segment. 85 Figure 29. Alternating Layers o f Rhodoliths and Fine Sands Stoma Layers. Picture Taken at Site D5S14 in Animas North Terrace Segment. 87 Figure 30. Horizontal Storm Layer in Large Coral Facies. Picture Taken a t Site D2S9 in Animas North Terrace Segment. 88 Figure 31. Cluster Tree of R-Mode Analysis o f Presence and Absence Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. XU counts of Genera found in Las Animas Pleistocene Deposits, Fossil Assemblages and Group Numbers are shown on left, side of figure. 92 Figure 32, Cluster Tree ofQ-Mode Analysis o f Standardized Genera Total Fossil Counts, Group Numbers, Biofacies, and Sample Sites are shown on the left side o f the figure. 96 Figure 33, Cluster Tree of Q-Mode Analysis o f Genera Presence and Absence Counts, Group Numbers, Biofacies, and Sample Sites are shown on the left side o f the figure, 99 Figure 34, Rancho Las Animas Terrace Map with Sites. Profile lines drawn through Terrace Segments. 105 Figure 35. StratigrapWc Picture, Schematic Diagram and fades of Site D2S9 in Animas North Tefface Segment. 106 Figure 36. Stratigraphic Picture, Schematic Diagram and facies o f Site D3S5 in Animas North Terrace Segment. 1.08 Figure 37. Stratigraphic Picture, Schematic Diagram and facies o f Site D6S8 in Km 26 Terrace Segment. 110 Figure 38. Stratigraphic Picture, Schematic Diagram, and facies o f Site D 6S 12 in Km 26 T©trace Segment. 112 Figure 39. Stratigraphic Picture, Schematic Diagram and facies o f Site D8S3 in Dune Terrace Segment. 114 Figure 40. Stratigraphic Picture, Schematic Diagram and facies of Site D12S6 in Dune Terrace Segment. 115 Figure 41. Stratigraphic Picture, Schematic Diagram and Facies o f Site R oad Cut. 117 Figure 42. Stratigraphic Profile o f Northern Animas North Terrace Segment. Legend Listed on the Sides. 119 Figure 43. Schematic Diagram o f Terrace Segment Animas North Middle Profile, Legend on Figure 42. 120 Figure 44. Schematic Diagram of Animas North Terrace Segment Southern Profile. Legend on Figure 42. 122 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Xllt Figure 45. Schematic Diagram of Km 26 Terrace Segment.Northern Profile. Legend on Figure 42. 124 Figure 46. Schematic Diagram, o f Km 26 Terrace Segment Middle Profile. Legend on Figure 42. 125 Figure 47. Stratigraphic Profile of Southern. Km 26 Terrace Segment. Legend, on figure 42. 126 Figure 48. Schematic Diagram o f Dune Terrace Segment Northern Profile. Legend on Figure 42. 129 Figure 49. Stratigraphic Profile o f Southern Dune Terrace Segment. Legend on Figure 42. 130 Figure 50. Schematic Diagram o f Typical Transgressive~Reg.ress.ive Fades Model. 134 Figure 51. Com.pari.son Graph of Grain Size Cumulative Weight Percentages at Three Different Localities. 149 Figure 52. 8234U(per mil) vs. Age (ka). Values o f Las Animas Forties are shown in comparison to Modem Corals. 157 Figure 53. Schematic diagram of amount o f uplift. 163 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. xiv Abstract Af Rancho Las Animas in Baja. California Sur, Mexico, are a series of terrace segments with Pleistocene deposits. Pleistocene deposits were examined at the three largest terrace segments named. Animas North, Km 26 and Dune. Fossil analyses, stratigraphy, grain size analyses, U-series age dating and uplift rates were investigated in order to determine the age, paleoecology and depositiona! paleoenviromnents o f the deposits. Several facies were identified that imply a transgressive - regressive cycle in. the terrace deposits. These facies, named Basal. Conglomerates, Fossiliferous and Reworked Cerro Colorado Member Sands, larg e Corals, Ponies, Molluscan and Rhodolith Sandy Marls, Fossiliferous Sands, Beach Gravels, Oyster Beds and Mounds, Small Pocillopora, and Storm Layers, record a sea level rise and fall in their sediment and fossil content. A typical stratigraphic column o f the transgressive - regressive cycle appears in the field as Fossiliferous and Reworked Cerro Colorado Sands, Large Corals unit, Porites, Molluscs and Rhodolith Sandy Marls or one its subfacies, Fossiliferous Sands and lastly. Beach Gravels. Grain size analyses define several trends in the depositiona! environments indicating changes in transport, deposition energy, and sediment populations, U and Tli isotopic analyses were done using a Fumigan-MAT 261 thermal- ionization mass spectrometer (TIMS). Age dating was determined using modifications o f methods previously reported in Musgrove et al (2001). U-seiies Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. XV ages found were similar to those found by other authors for late Pleistocene terrace deposits on the 'eastern Baja California peninsula. Ages for Rancho Las Animas terrace deposits range from 120 ka and 145 ka, suggesting that they correlate with the late interglacial high stand. Using terrace heights and U-series ages, uplift rates o f 8 to 15 em/ka were determined for the Rancho Las Animas terrace deposits. This range o f uplift is similar to other localities in the Baja California region. The major difference between the paleoecology identified in the Rancho Las Animas terrace deposits and the modem environment in the Gulf o f California is the presence o f large branching growth forms of Forties pm um em is. These large morphologies o f P. panamemis are not found in the Gulf today, suggesting that changes in the sea surface temperatures may have influenced the difference in coral growth. Since this species of Forties is adapted to not only cooler waters but also a larger range o f sea surface temperatures, it may indicate that both the late Pleistocene winter and summer temperatures may have increased, although the temperature range did not change. This pattern of temperature change would have allowed the thermally varied Forties panamemis to dominate the coastlines instead o f Pocillopora elegans that requires a smaller seasonal thermal range. Other factors such as increase in salinity and sedimentation may have also played a role in the dominance o f Forties panamemis over the modem day dominant Pocillopora elegans. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1 Introduction During the last interglacial epoch, between about 80,000 to 130,000 years ago, sea level stood higher than at any time in the last 350,000 years (Shackleton, 1.969; CLIMAP, 1984; Ashley et al., 1987; Sirkin el. al., 1990; Szabo et al., 1991; Gallup e t al., 1994; Johnson and Libbey, 1.995; Stirling et al., 1995; Neumann and Hearty, 1996; Ortleib, 199.1; McCulloch and Esat, 2000; Kukla et al., 2002), This interpretation o f sea-level changes is based on fluctuations in oxygen isotopic ratios from both benthic and planktonic foraminifera in Upper Pleistocene deep-sea cores (Shackleton, 1969;Emiliani .1970; CLIMAP, 1984; Chappell and Shackleton, 1986; Mix, 1987; Kukla et al., 2002). In general, oxygen isotope Substage 5e (MIS 5e) is the last time the isotopic values were as light as they are today. It is believed that Substage 5e was the last time that the volume of ice on earth was as small as it is today (CLIMAP, 1984; Kukla et al., 2002; Shackleton et al., 2002), The receding of the M IS 5e high stand, left remnants o f the ancient shoreline in the form of terrace deposits, which are found today all over the world. These terrace deposits come in many shapes and. sizes, from small sandy beds to large Pleistocene reef complexes (Chappell, 1974; Kaufman, 1981; Ashley et al., 1987; Woodroffe et al., 1991; Gallup et al., 1994; Blanchon and Shaw, 1995; Neumann and Hearty, 1996; Stirling e t al., 1998: McCulloch and Esat, 2000; Muhs et al., 2002). Of particular interest are marine deposits with hermatypie corals. Since corals are environmentally sensitive, the presence of a coral reef or bioherm can be used to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ‘ 1 <& * interpret environmental conditions (e.g. water depth, salinity, sea surface temperatures, water clarity, wave energy, etc,; Chappell, 1980; Stirling et a l, 1998; MeCulloch and Esat, 2000; Spalding et a l , 2001; Muhs et al., 2002). Also, because skeleton-secreting corals take in many elements from the seawater, they can be used for many geochemical analyses such as age dating, sea surface temperatures, and salinity (Ashley et a!., 1987; Gallup et a/., 1994; Neumann and Hearty, 1996; Stirling et al., 1998; MeCulloch and Esat, 2000; Fenberg and Goodwin 2002; Mayer et al., 2002; Muhs et al., 2002). These Pleistocene coral bioherms are found in the tropical and subtropical regions of the world as wave cut terraces such as those found in the Huon Peninsula in New Guinea where tectonic uplift has pushed onlapping MIS 5e terraces over 200 meters above sea-level (Chappell, 1974; MeCulloch and Esat, 2000) or carbonate platforms like those found in Jamaica with thin layers of corals pushing up onto the drowning Pleistocene coastline (Kaufman 1981). Along the coastline of the Baja California peninsula in Mexico (Figure 1), especially on the eastern side between Santa Rosalia and Cabo Pulmo, are Neogene and Quaternary terraces, commonly including marine deposits from the last interglacial sea level high stand of marine isotope stage (MIS) 5c. These terraces are wave-cut benches or small platforms. Most of the Pleistocene deposits are erosional remnants, best exposed in sea cliffs and arroyos and consist of thin layers of sand and gravel with broken molluscan, echinoderm shells, and coral and algal Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 Pacific Ocean l.ii s - 'c r /* - Mexico Figure t. Map of Baja California with Close Up of Terrace Locality. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 fragments (Squires, 1959; Johnson and Ledesma-Vasquez, 1999; Ransom, 2000; Ledesma-Vasquez and Johnson, 2001), Rancho Las Animas is located in the southern part of the Baja California Peninsula approximately 70 km north o f La Paz. At this locality there are a series of terrace segments covered by Pleistocene deposits. Deposits extend 3 km inland and 32 km along the coastline of Bahia del Coyote and from El Saladito to Punta Coyote (Figure 2). Many studies o f Pleistocene deposits on the Baja California Peninsula have been conducted on terraces located throughout the Baja Peninsula: in the northern Gulf of California (Ortlieb, 1991; Allmon et a l, 1992; Goodwin et a l, 2000), the central western coast of the Gulf (Ashley et a l, 1987; Libbey and Johnson, 1997; Meldahl et a l, 1997; Johnson and Libbey, 1,999; Johnson and Ledesma-Vasquez, 1.999; Ledesma-Vasquez - Johnson, 2001), the southern Baja coast o f the Gulf (Squires, 1959; Sirkin et a l, 1990; Ransom, 2000; Fenberg and Goodwin 2002; Mayer et a l, 2002), and the Pacific side of the Baja California Peninsula (Woods, 1980; Johnson et al., 1996). What makes these deposits in Rancho Las Animas unique from other Baja California Pleistocene deposits are their previous inaccessibility, large sections, almost complete regressive cycles, great preservation (corals tested at >98% aragonite pure), and deposits with large areal extent. Until the construction o f a road in the mid-1980s, the Rancho Las Animas area was accessible only by boat, leading to very little field research. The marine sequence at Las Animas contains numerous facies indicative to a regressive cycle and, possibly in some sites, to the previous transgression. At many localities, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 R oad C ut Student Locality D une Km. 26 A nim as N orth 1 km Figure 2. Map of Rancho Las .Animas Terrace Segments. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6 the units within this marine sequence measure over 10 meters in height. One of the most interesting units found in the Las Animas area is that of the thick coral beds (>10 in) of Pontes panamensis with individual branching coral heads as big as 2 meters in height. Although P, panamensis has been found in other Pleistocene deposits as far north as Punta Cbivato (Ransom, 2000), the thickness of the coral beds are not common (most nearshore Pleistocene deposits found in the Eastern Baja Peninsula are up to a couple meters in thickness; Squires, 1959; Johnson and Libbey, 1997; Ransom, 2000). Even in the modern. G ulf o f California, P. panamensis do not grow to the sizes observed in the Las Animas Pleistocene deposits. Most P. panamensis are approximately the size o f a finger, growing on rocks in the lower intertidal or in small coral patches or thickets in shallow waters (Steinbeck and Ricketts, 1.941; Durham, 1947; Squires, 1.959; Brusca, 1980; Glynn and Wellington, 1983). Not only are the Las Animas deposits thick, but they also encompass large areas on top o f the terraces. Pleistocene deposits can be followed for hundreds of meters both around and over the terrace segments, unlike other localities on the Baja coastline that are generally comprised of wave-cut cliff facings (Durham, 1950; Squires, 1959; Ashley et ah, 1987; Sirkin et ah, 1990; Johnson and Libbey, 1997; Ransom, 2000). This unique aspect of the Las Animas terrace segments allows fo r a third dimensional perspective o f the deposited facies. The Rancho Las Animas terrace is not only unique in comparison to other MIS 5e Pleistocene terraces in Baja California, but to other terraces as well. In Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 general, most late Pleistocene terraces are wave-cut: cliff facings and platforms that might reach several meters inland such as those at Yardie Creek and Burney Point in West Australia that are 10 20 meters wide (Stirling et al., 1998), or at the reef platform in the Falmouth formation in Jamaica (Kaufman, 1981). So what makes the terrace at Rancho Las Animas so unique? The third dimensional structure, although found in other localities (e.g. Cook Islands, Barbados), is not a common structure. Several distinct facies representing different environments can be determined from the Las Animas terraces. Also, unlike other late Pleistocene terraces, which contain coral bioherms and reefs comparable to their modern equivalences, the large coral bioherms found in the Las Animas terrace segments do not represent arty modem environment found within the Gulf. O bjectives T he purpose o f this research is three part: first to document the stratigraphic relationships and to interpret the faunal paleoecology of the Rancho Las Animas Pleistocene deposits, second to identify if there are any differences between the modern and Pleistocene environments, and third to determine the underlying reasons as to why there are differences. This wall be done using faunal assemblages (faunal identification, statistical analyses), stratigraphy, sediraentology (grain size and sedimentary structures analyses), and geochemical data (Th/U age analyses). Because of the size of the field area (32 km along the coastline), the three best terrace segments from the Rancho Las Animas area were chosen based Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 on size, outcrop preservation, and stratigraphic extent both horizontally and vertically. These segments, named by features and location in the field are called Animas North Terrace, Km 26 Terrace, and Dune Terrace (Figure 2). Study Location The Peninsula of Baja California (Mexico) is a long, narrow, landmass approximately 1000 km long and 100 km at its widest (Figure 1). Baja is bordered bv the Paci fic Ocean to its west and by the Gulf o f Cali fornia to its east. The steep Gulf coastline is interrupted by the low isthmus at I,a Paz and by large alluvial fans. In the southern part of the peninsula (Baja California Sur) approximately 70 km north of La Paz and 20 km north o f San Juan de la Costa, is the gulf coast desert region of Rancho Las Animas. The terrace at Rancho Las Animas is composed o f coastal sand dunes, Pleistocene marine deposits, and Miocene offshore to non-marine deposits. The Pleistocene deposits are composed of siliciclastic sands, carbonate debris, rhodoliths and muds filled with bivalves, gastropods, and corals. The Pleistocene deposits overlie the (Oligocene to Miocene) the San Juan and the Cerro Colorado Members of the El Cien Formation (Fischer et al. 1995). The focus of this study, are the three largest terrace segments plus a couple of the outer lying localities (e.g. Road Cut). Animas North Terrace, named for being north o f Rancho Las Animas, is approximately 0,81 km at its widest and 1.83 km in length. A map of Animas North Terrace is illustrated in Figure 3. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. • 24°33'00" ■ 24”32'30“ Animas North ? SS4 D5S* DiS2. D1S3 T n ..'' f D5S,Q ‘ ^ D 1 S 4 * | . £55 | j «vA 5 rS '*B5S2 *D 5 S 7 " » DtSL' DS§( dis& a DiS 7 d is h - p - ’H fe tfp p sw J.D1S10 -.LAS-t “ -*D 1S12 * . T V N 2 1 n js n « .'* D!Sl U JS U , D 2 S 1 ' , D2S2 »D2S3 { .D 2 S 4 D2S6, D2S7s ■t)2S5 i D5SI4t ^ - n>5Sl3 i *D2S9 D 2 S S > -> D2S12 D 2Si3 . t ■ n; ^ ■ ' DZSIO' , D2S11 1 k m D 4S2 s i J 4 3 1 3 * v , D 3 S 2 D 3S5 D 15& . D * . - ; m “ • D 4S4 \ D3S«‘ iie=45’ o r LAS-0! Figure 3. Site Map for Animas North Terrace Segment. Bahia de La Paz 11P44W 10 Elevation varies through out the terrace with the east side slightly higher than the west (1 - 2 m). General stratigraphy shows that the large coral facies developed mainly on the western side and in channels. The typical pattern here, from bottom to top, is the Cerro Colorado Member at the bottom, conglomerate facies, reworked Cerro Colorado fossiliferous sands, rhodolith and molluscan sands and coquina and either fossiliferous sands or beach gravels capped with younger coastal dunes. Km 26 Terrace, located just north of Animas North Terrace and at the 26 km roadside marker, is two smaller erosional remnants with a small channel separating them (Figure 4). It is approximately 1.2 km in width and 0.91 km in length. Stratigraphy at this segment indicates that the large coral facies is predominant in the southeastern and northwestern sides o f the terrace, with the coral facies only appearing in lower areas. Coral facies here are generally capped with fossiliferous sands or ''pencil" Porites and molluscan sandy marls, with the modern dune as the final unit. Dune Terrace, the segment furthest north, is named for the large dune separating the terrace from the beach. This segment, the smallest of the three terrace segments, is approximately 0.91 km in width and 0.72 km in length (Figure 5). Dune Terrace is a large, many lobed crescent-shaped area with the general pattern from bottom to top of large corals, “pencil” Porites and molluscan sandy marls, fossiliferous sands and beach gravels. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. o Oj \ vs# n i < / > > O O t O P y t\ o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F igure 4. M a p o f K m 2 6 T errace Segment w ith S ite Locations. 1 .2 O 5 /3 • « /> M 3 O * / T o o < r i o © r O Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F igure 5. M a p o f D une T errace Segment w ith Sites. 13 Geological Setting Baja California Tectonics The Baja California peninsula developed in three phases starting in the Miocene (Ledesma-Vazquez and Johnson. 2001). The first phase of the Baja Peninsular development, occurring from 24 to about 12 Ma, was the subduction regime active on the Pacific coast during Baja California Miocene time (Ledesma- Vazquez and Johnson, 2001), The Farallon-Paciflc spreading system approached the trench, the subduction steepened and the volcanic activity to migrate westward, arriving along eastern Baja California. This movement was accompanied by uplift of the Baja platform and near-coast subduction (Atwater, 1989; Nava-Sanchez et a!., 2001 ), Later, portions o f the subduction zone became completely subducted. The second phase was a major episode of crustal extension related to the opening of the Proto-Gulf (10-3.5 Ma), which is associated with the Basin and Range development of the western North America Miocene (Ledesma-Vazquez and Johnson, 2001). After the subduction, the activity of the volcanic arc east of Baja California ceased in Late Miocene time. A strike-slip motion to the NNW, along the right-lateral San Benito-Tosco-Abreojos faults, characterized the Pacific-North America boundary. The Pacific Rise rotated clockwise at the southern end of this boundary until the ridge-trench-transform triple junction was stabilized in the area that is now the mouth o f the Gulf. North of this triple junction, the proto-Gulf extension occurred as a zone o f graben formation (Nava-Sanchez et a l, 2001). The third and final stage is the transtensional regime responsible for the present tectonic Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14 configuration in the Gulf o f California and the transfer of Baja California to the Pacific Plate from the Miocene North American Plate (Ledesma-Vazquez and Johnson, 2001). By 3.5 Ma, a majority o f the motion between the Pacific plate and the Mexican mainland was transferred from the Toseo-Abreojos fault to the proto- Gulf, and the Baja Peninsula was transferred from the North American Plate to the Paci fic Plate. Right-lateral shearing with in the G ulf accelerated, and spreading rotated counterclockwise, starting a pattern of new enechelon transform faults oblique to the overall trend of the Gulf. During the last million years, vertical movement along the eastern margin has been relatively minor and the area has been more or less stable, whereas the peninsular block has been subjected to a slow and fairly continuous uplift of about 100 mm/ka (Ortlieb, 1991; Nava-Sanchez et a/., 2001). The uplift however, is not uniform all along the peninsula, but can be decreased or increased by local processes (Ortlieb, 1991). The most deformed and uplifted areas are located close to the main fracture zones. The last interglacial shoreline in eastern Baja California is generally well identified, although elevations differ (Ortlieb, 1991). Elevations from northern to southern Baja range from +6 m in the La Reforma-Santa Rosalia area to + 30 m southeast o f Bahia de La Paz. The differences between highstand levels along the eastern B aja coastline are believed to be the result o f regional uplift (Ortieb, 1991). It is unclear how much o f these variations in Pleistocene terrace elevation are due to eustatic- sea-level change or to subsidence and uplift. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15 Rancho Las Animas Geology Rancho Las Animas is located on the eastern side o f the Sierra de la Giganta Mountains in the southern part o f the Baja Cal ifornia Peninsula. Like most of the southern part of Baja, Tertiary elastic sedimentary rocks are exposed, forming a wide synciine. The base of these beds is the bioturbated silt: and sandstones of the Late Cretaceous - Eocene Tepetate Formation. Sitting unconformably on top o f the Tepetate Formation is the Oiigo-Miocene El Cien Formation. The El Cien Formation is broken into two subunits: the San Juan Member and the Cerro Colorado Member (Figure 6). Previous studies have listed these members as San Gregorio and Isidro Formations (Hausback, 1984; Kim, 1987), and even older studies have listed the San Gregorio as the Monterrey Formation (Darton, 1921; Beal, 1948). For the purpose o f this research these units will be called the El Cien Formation with San Juan and Cerro Colorado Members as subunits in accordance with the research done by Gidde (1992) and Fischer et al. (! 995 ). The bottom of the San Juan Member (Upper Oligocene) begins with a sandy conglomerate with fossils. Bedding structures vary from nearly horizontal to flaser and ripple bedding with bioturbation. The middle section of the San Juan Member is fine-grained sediments filled with beds of laminated siltstones, partly tuffaceous, silicious, diatomaceous or phosphatic mudstones rich in brown fish scales, w hite to gray tuff, minor intercalations of silt and sandstone, and granular phosphorite beds (Fischer et a l 1995). The upper part of the San Juan Member is composed o f fine- to coarse- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C A N A D A “ “ ““ Upper Miocene ASUA a m a b q a TABA8HUS COMOND0 « FORM ATION Lower Miocene 1 •ay'vwi f-} !^ K « ersr: 5 .ir # ■ . ? « * S V l ' S F i s * ' * " : * 9 ? San Juan SSSr-rii Upper Oligocene Figure 6. Stratigraphic column of Tertiary Formations, El Cien and Comondoc, From Outcrops Just South of Rancho Las Animas. (Taken From Fischer et al. 1995). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1? grained sandstones interbedded with muddy siltstones, pebbly sandstones or conglomerates and a few coquinas. The boundary between the San Juan and Cerro Colorado members is marked with an abrupt change from the coarse-grained sandstones and conglomerates to finer-grained sand- and siltstones. Above the finer-grained beds, the Cerro Colorado (Lower Miocene) changes to fine- to coarse-grained sandstones with storm deposits and coquinas interbedded. In the eastern part of the El Cien Formation, the Cerro Colorado Member ends with green sandstone beds. This bright green color is due to a mineral called celadonite (Gidde, 1992; Fischer et al., 1995). Celadonite occurs as first generation cement, in the form of a green coating. Sometimes, the celadonite forms second-generation cement that fills interstitial spaces almost completely during an early phase in diagenesis. Overlying on the El Cien Formation are the volcaniclastic- rocks of the Comondu Formation (Upper Miocene). In the Rancho Las Animas area, the landscape consists o f alternating ridges of El Cien Formation and arroyos filled with all uvial sediments and conglomerates from the tall cake-like buff and brown layers of the Comondu Formation in the Sierra de la Giganta to the west (Figure 7). The only thing interrupting this landscape are the isolated Pleistocene terraced mounds, separated by arroyos along the eastern coastline (Figure 8). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18 Figure 7. Buff and Brown Layers of Comondu Formation Seen in the Sierra Las Tarabillas in the Background. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20 Background M odern G ulf of California N earshore Communities In the Las Animas area, the most common fossils found in the Pleistocene deposits are molluscs (bivalve, gastropod, and occasional scapbopod), corals, echinoderms (sand dollars or sea urchin spines), and rhodoliths. In order to understand bow these organisms in the Pleistocene deposits relate to modern equivalents, an understanding o f their modem environments and relationships is needed. The Gulf o f California or the Cortez Province is one of several regions that form the eastern Pacific faunal assemblages. The provinces are, the Panamic province (Tangola-Tangola Bay, Mexico to the Gulf of Guayaquil, Peru), the Mexican province (mouth of the Gulf o f Ca lifornia to Tangola-Tangola Bay, Mexico), the Cortez province (the Gulf of California), the Californian province (Point Concepcion, California to the Pacific tip of Baja California, Mexico), and a few m ore provinces further north on the North American coast (e.g. Oregonian, and Alaskan). The Eastern Pacific is considered to have some of the distinctive communities in the world. This is believed to be due to the East Pacific Barrier and the formation of the Isthmus of Panama (Darwin, 1842; Glynn arid Wellington, 1983; Grigg and Hey, 1992; Cortez, 1997; Glynn and Ault, 2000; Spalding et al., 2001). The East Pacific Barrier, named by Elkman (1953 ), is an expanse of ocean where no islands exist in the tropical Pacific separating the Indo-Pacifie Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21 zoogeographie province from the eastern Pacific province. This barrier has been termed as an impassable barrier for migration o f coastal marine species (e.g. larval transmission). Before formation of the Isthmus, the western Atlantic arid the eastern Pacific were in communication and the fauna! communities were a mixture of genera that are now characteristic of either the Caribbean or the Indo-Pacific (Glynn and Wellington, 1983). Each o f these provinces form regions that are populated by a distinctive assemblage of species. Al though species that populate these regions form distinct assemblages, many species are not restricted to these provinces and can be found in several. In the Cortez province, 21% of species found are endemic, 41% are from eastern tropical Pacific regions (Mexican and Panamic provinces), 18% are temperate (Californian and Oregonian), 1% are Indo-Pacific, 4% are amphiAmerican (Caribbean), 8% are cosmotropical and cosmopolitan, and 7% are unknown (Brusca, 1980). This demonstrates the wide variety of marine invertebrates that can live in the Gulf of California. There are three principal factors that influence the local distribution of intertidal invertebrates: 1) amount of wave action, 2) bottom type, and 3) tidal exposure (Ricketts et al., 1939; Brusca, 1980). By varying the combinations and degree o f these three (actors, one can come up with e very conceivable type of shoreline habitat. In the Gulf of California, waters form two distinctive regimes, the northern hot summer temperatures with cold winter temperatures and the southern, warmer winter temperatures. This, in combination with the three principal Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■ y > Ji.r.' (f factors previously listed, allows the coastal ecology in the Gulf of California to consist o f a great diversity in shore types, The most common of these are rocky shores, sandy beaches and tidal flats (Brusca, 1980). O f the three types of habitats, rocky shores have the most diverse fauna, ranging from barnacles to corals to crabs and sponges, and most common. Common invertebrates found on the exposed rocks o f a rocky shore environment are barnacles (Balanus, Chthalamus, Tetraclita), coiled worm tubes { Hydro ides, Spirorbis), and snails (Littorerina, Nerita, Collisella, Columbella, Acanthina). Rocks uncovered during the lowest tides may reveal green corals (Porites panamemis), sea anemones (Bunlodactis, Anthopleura, Bunodosoma, and Phyllactis), and sea stars (Othilia tenuispina, Phataria imifaeialis, and Pharia pyramidata). Found in between the rocks are crabs (Eriphia and Gmpsus) and sea urchins (Echinometra m dE ucidam ). The bottoms o f the rocks are also home to many animals, such as sponges, sea cucumbers, sea stars, brittle stars, flatworms, opisthobranchs, polychaete worms, porcelain crabs, gastropods, chitons, and true crabs. Living in the environments of the tidal flats are mud snails (Cerithidea, Natica, Nassarius), and if there is enough sand olive shells (Oliva and Olivella). Tubes o f polychaete worms (Diopatra, Chaetopterus, Arenicola) can be found protruding from the surface. Below the surface o f the mud/ sandy mud are a variety o f polychaetes, shrimp, isopods, and peanut worms. There are also many animals that live in the water channels that cut through the tidal flats carrying water to and from the gulf. In these channels there can be found beds of sand dollars Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23 (Encope, Mellila, C/ypeaster), some gorgonian coral, and occasional sea pens. Buried in the sand are also numerous clams (Chkme, Protothaca, Tagelus). In the central and southern Gulf, tidal flats often have smaller enclosed bodies of waters inhabited by mangrove trees. These mangrove regions are unique in that they are almost always found in esteros (negative estuaries where evaporation exceeds precipitation). Mangroves commonly found in these environments are the Red Mangrove (Rhizophora mangle), the Black Mangrove (Avicennia germinans), and the White Mangrove (Laguncularia racernosa). Also found with the mangroves are Sweet Mangroves (Maytenus phyllanthoides), which are not considered a true mangrove but a tropical shrub. Invertebrates typically found in the mangroves are sponges { Litaspongia and Ophlitaspongia), brown anemone, oysters (especially Ostrea columbiensis and O. palmuki), shipworms, certain gastropods (Cerithium stercasmuscarum, Crepidula spp., and Crucibulum spp.), barnacles, crabs, brittle stars, and tunicates. Although not as abundant as the other habitats found in the Gulf, sandy beaches also contain many different invertebrates. Ghost crabs can be found burrowing above the water line. The low tide can reveal burrowed mole crabs, little clam s, amphipods, and isopods. Very low tide unveils sand dollars, heart urchins, large sand stars, polychaetes, and a few swimming crabs. A more in-depth description of the common Pleistocene species found in the Las Animas area (i.e. molluscs, corals and rhodoliths) follows. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24 Coral Communities The eastern Pacific Coral provenance extends from the northern coast of Peru to the Gulf o f California. Up until the 1970s, this region has been cited as a region devoid o f corals reefs (Darwin, 1842; Cortez, 1997). The coral reefs of the eastern Pacific are typically small, with discontinuous distribution and low species diversity. This is in part due to the harsh conditions for corals in the Eastern Pacific. There are numerous factors that are important in controlling coral distributions and species diversity. These factors include light, sedimentation, temperature, salinity, storms or wave energy, tidal exposure, nutrient availability, space competition, and grazing by herbivores and corallivores (Porter, 1974: Chappell, 1980; Huston, 1985; Spalding et al., 2001). The cooler water temperatures, upwelling, and the limit o f suitable sediment substrates make the eastern Pacific an unfavorable environment for reef building corals (Glynn and Colgan, 1992; Cortez, 1997; Glynn and Ault, 2000; Spalding et al., 2001). Today there are 124 species of corals in the eastern Paci fic, 52 genera and 15 families (Reyes-Bonilla, 2002). From these 124 species, 82 are azooxanthellate (ahermatypic) and 42 are zooxanthellate (hermatypic). These numbers are small in comparison to the Western Atlantic (62 species of scleractinian corals) and the Indo-Pacific (719 species of scleractinian corals) (Spalding et al., 2001). These small num bers are the results of two factors: the formations of the Isthmus of Panama and the East Pacific Barrier. Approximately 89 percent o f eastern Pacific fossil coral species previously lived in the Atlantic and 40 percent in the Indo- Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25 Pacific (Glynn and Wellington, 1983). However, Pliocene/Pleistocene glaciations caused the extinction o f many eastern Pacific coral species, weaken ing the species affinity between, the Atlantic and the eastern Pacific. Recolonization of the eastern Pacific from the Indo-Pacific species, although slow and sporadic due to the East Pacific Barrier, increased the relationship between the two regions. Currently the best hypothesis to explain the distinct reef building coral fauna in the eastern Pacific is given by Glynn and Ault (2000). For years it has been argued as to which is the best hypothesis for the distincti veness of tropical eastern Pacific coral faunas: long distance dispersal or vicariance. Long-distance dispersal, as proposed by Glynn and Wellington (1983) assumes that the eastern Pacific region has been colonized relatively recently by the long distance dispersal of larvae, from the Indo-Pacific by way of the north equatorial counter current. Vicariance, on the other hand, states that the eastern Pacific fauna was derived from pan-Tethyan, western Atlantic species that were present before the closing of the Panama isthmus (Heck and McCoy, 1978). Glynn and Ault (2000) examined both of these hypotheses and proposed that the Modem eastern Pacific coral fauna may be a mixture of both processes. Most of the faunas are Indo-Pacific migrants that reached the east Pacific by long-distance dispersal (via the central Pacific islands) after the formation of the Isthmus of Panama. There are also several endemic species that have evolved in the isolated and marginal eastern Pacific environments. And lastly, there are a few relict species with affinities to the western Atlantic. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 26 The eastern Pacific region, where reef-building corals are found, is divided into four biogeographical provinces, Cortez, Mexican, Panamic, and Galapagos (Glynn and Wellington, 1983; Cortez, 1997). The Cortez province is located within the G ulf of California. This region is characterized as subtropical and is great ly influenced by the continental climatic conditions o f the Sonoran Desert. The latitudinal warming increases and seasonal extremes in temperatures decrease southward in this region (Glynn and Wellington, 1983). The Mexican province start s in the south at Tangola-Tangola Bay and extends north to the Gulf of California. The Mexican province is separated from the Panamic province by the Pacific Central American Faunal Gap (PCAFG). This is a segment of sandy beaches and coastal lagoons where no coral reefs have been found. This is due to lack of hard substrate along the coast, which inhibits the growth of corals (Glynn and Wellington, 1983). The Panamic province is located from the Gulf of Guayaquil to the Gulf of Tehuantepec (just north of the PCAFG). This province contains the highest diversity in the tropical eastern Pacific. The Galapagos province shows strong affinities to the Panamic province (Glynn and Wellington, 1983). A ll reef building coral species found in the Galapagos province are found in the Panamic province as well. Other marine invertebrates, such as the echinoderms and crustaceans, also show strong affinities with the Panamic province. Although, there are many similar species between the Galapagos and Panamic provinces, there are still many more species that are endemic to the Galapagos province, indicating the amount of speciation that has occurred there. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 27 In the eastern Pacific, coral communities and reefs are generally dominated by one to three extra! species (Glynn and Wellington, 1983: Glynn and Colgan, 1992; Cortez ,1997). These reefs and communities are usually small, have discontinuous distributions and low species diversity. The two main types o f coral reefs found in the eastern Pacific are pocilloporid reefs and poritid reefs (Cortez, 1997). In general, reefs are commonly small, monospecific thickets of Pocillopora or massive colonies oiPorites and Pavona usually 5-6 m high and 150 m wide (Glynn and Colgan, 1992). In the Galapagos province, modest pocilloporid buildups (Pocillopora damicornis) were the most common. There are also a few Pavona clams buildups and one Porites lobata (Glynn and Wellington, 1983). All reef-building corals found in the Galapagos province and about 25% of the ahermatypic corals are also found in the Panamic province (Glynn and Wellington, 1983). In the Panamic province, 23 different hermatypic coral species have been found (S palding et al., 2001). Most of the reefs in this region have either shallow banks o f Pocillopora or Porites lobata as the major reef-builders. Coral communities in the mainland Mexican province are well developed but are composed of only a few species, mainly Pocillopora spp., Porites spp., Pavona spp., Psammocora sp., and Fungia spp. (Spalding et al., 2001). The Mas Revillagigedo. considered part of the Mexican province, contain the most diverse fish and coral communities in the Mexican Pacific, Although the reef development is lim ited in the Islas, there are 23 hermatypic coral species, dominated by Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28 Pocillopora spp,, and some Porites lobata and P. lichen (Reyes-Bonilla and Lopez- Perez, 1998; Spalding et a l 2001), This region also has one endemic species, Porites haueri (Reyes-Bonilla, 1993; Reyes-Bonilla and .Lopez-Perez, 1998), O f all the zoogeographieal provinces, the Cortez province is considered to have some o f the harshest: conditions for coral growth with high salinities and cooler winter temperatures than other provinces (Reyes-Bonilla, 1993). In the early 1990s the list o f hermatypic coral species in the gulf decreased to 12 as more studies examined the corals and their morphologies (Reyes Bonilla, 1992), From a series of trips to the Gulf, Reyes Bonilla (1992) reported new geographical ranges for seven o f the 12 coral species. He determined Pocillopora damicornis to be further north (e.g. San Juan de la Costa) than where Squires (1959) reported in El Pulmo Bay. Reyes Bonilla also reported that this species, although dominant in most Central American Pacific communities, is uncommon in the Gulf. Pocillopora elegans, became P. verrucosa under Reyes Bonilla studies, agreeing with Brusca and Thomson's report that this is the most abundant coral in the G ulf south of 26 N. He also notes that Porites californica is synonymous with P. panamensis (1992). Opinions on the number of coral species living in the gulf vary. Glynn and Ault (2000) eight years after Reyes Bonilla's paper have 18 coral species in the G ulf. They also insist that several of the coral species synonymized by Reyes Bonilla are different species (e.g. Pocillopora elegans and P. verrucosa are Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 different taxa). This has led to confusion as to the correct identity for some coral species in the Gulf. The principal species of corals in the coral communities and coral buildups in the southern part of the Gulf are Pocillopora verrucosa (synonymous with Pocillopora elegans - Reyes-Bonilla, 1992), Pocillopora damieornis, Porites panamensis (synonymous with Porites californica - Glynn and Wellington, 1983), Pavona gigantea, and Pavona clavus. The primary reef-builder is Pocillopora (Figures 9 and 10), while the most common fringing coral community corals are Poritespanamensis (Figure 11) (Glynn and Wellington, 1983). Several small coral patches or thickets have been found in the southern half o f the G ulf (Steinbeck and Ricketts, 1941; Durham, 1947; Squires, 1959; Glynn and Wellington, 1983). Only isolated colonies o f Porites panamensis and P. sverdrupi can be found in the northern part, P. panamensis is considered a unique species because it inhabits all areas o f the Gulf. This coral is believed to be adapted to the lower temperatures that can occur in the gulf (Reyes-Bonilla, 1993). Porites sverdrupi is also unique in the sense that it is endemic to the gulf (Reyes-Bonilla, 1992 and 1993). Porites sverdrupi is believed to be a descendant from some Porites predecessor from the Atlantic. Since there is evidence that P. sverdrupi has been decreasing in population for the past thousand years, it is believed that it is becoming extinct through natural processes (Reyes-Bonilla, 1993). O f all the coral communities in the Gulf only El Pulmo is considered a reef (Brusca and Thommson, 1977). In the past the coral communities at El Pulmo Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 9. Modem Pocillopora sp. washed up on a Beach in El Coyote. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 10. Photo o f Pocillopora elegans Coral heads near i> ia Kpiritu, Ldliioma Sur, Mexico. 32 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission Sur, Mexico. 33 have not been considered true reefs in constructional sense (Squires, 1959). Brusca and Thomson (1975) however after several years o f collection and observation of the El Pulmo communities believe that the coral communities at El Pulmo are constructional. The species richness and coral associations with other fauna and flora also are consistant with other reefs. Brusca and Thomson also point out that although the El Pulmo reels do not appear to contribute to the local beach sediments it is possible that this is only due to the youthfulness of the reefs (“ 5000 years old). For years the youthfulness of Gulf coral communities have been remarked on (Squires, 1959; Brusca and Thomson, 1977; Glynn and Wellington, 1983). Comparing the growth rate of similar species in the Gulf o f Panama to the ones in the G ulf of California, Brusca and Thomson (1977) estimated the reef of El Pulmo to be less than 20,000 years old and possibly less than 5,000 years old. Using the same methods, Glynn and Wellington (1983) estimated the build up at Los Frailes Bay and San Gabriel Bay to be no older than 2,300 and 1,900 years old, respecti vely. Most reefs around the world are generally younger than 5,000 years. The Gulf of California hermatypic fauna consists of 15 species in five genera (Reyes-Bonilla, 1992). Only five of these species do not have synonyms: Pavona gigantea, Psammocora hrighami, Psammocora stellata, Porites baneri, and Porites lobata (Reyes-Bonilla, 1993). More than half o f the 15 hermatypic coral species have a fossil record. Comparison of the percentage of Recent species with a fossil record in different places in the Pacific America indicates that the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34 coral fauna o f the Gulf is the oldest one in the eastern Pacific. Regions of large communities of corals in the Gulf o f California are El Pulmo, Los Frailes Bay, Punta Chilcno, San Gabriel Bay, Puerto Escondido, Aqua Verde Bay, Salinas Bay. As stated before, these communities change with latitude in the Gulf. A comparison description of two of these communities, El Pulmo and Puerto Escondido, demonstrate the distinct differences. El Pulmo Located inside the Gulf near the tip o f Baja California, El Pulmo reef is a series o f submerged, parallel, rock ridges extending offshore in a northeasterly direction (Squires, 1959; Brusca and Thomson, 1977; Glynn and Wellington, 1983 ). These ridges (eight in all) are made of extruded igneous rock (Squires, 1959). The outermost reef is 8 to 10 m in depth at the southern end and about 22 m at the northernmost end. The depth of the sandy area between the ridges at the southern end is about 17 m. The coral communities are locally concentrated on the rock ridges. Compared to any other coral community in the Gulf, El Pulmo has the most hermatypic coral abundance with 10 of the 15 Gulf species (Reyes-Bonilla, 1993 ). Coral coverage of the reef has fluctuated between 30 - 40% from 1987 - 1991 (Reyes-Bonilla, 1993). The primary reef-building coral is Pocillopora verrucosa at the shallowest depths and Porites panamensis and Pavona gigantea in the deeper parts. Pocillopora spp. make up about 80% of the corals. The corals occur from near extreme low tide level to at least 10 m. Occasional growths of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35 Pavona clivosa and P, gigantea are present, as are Pocillopora verrucosa and other species. Pontes is also common on the reefs and is found in three different growth forms depending on the local environmental conditions: a thin encrustation, a squat or tall columnar formation, or a tall stalklike growth (Brusca and Thomson, 1977). The coral fauna is most abundant in the margins of the ridges, with lobed and bladed coralla o f Pavona up to 3 feet in diameter being the dominant coral, and small, hemispherical coralla of branched Pocillopora damicornis and P. verrucosa were extremely abundant. The areas between the ridges are inhabited by much of the same fauna as on the margins, with domed coralla Porites as the most common coral. In shallower waters, all species become less abundant and only Pocillopora and Porites able to withstand the surf action. Puerto Escondido In the inner harbor of Puerto Escondido, approximately 2 m laterally from the mangroves, was a thin but persistent line of Porites panamensis in about I m of water. These large, pinnacled growth forms of Porites fronted the mangroves for a distance of about 100 feet (Squires, 1959). No where else in this bay is this growth form found although Porites is widely distributed. The differences between El Pulmo and Puerto Escondido are very large. The southern coral community, El Pulmo, has a larger size (both in laterally and horizontally) and variety of corals when compared to the more northern community Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36 in Puerto Escondido. This demonstrates how much the factors for favorable coral growth decline in the northern Gulf. Gulf Molluscan Communities Molluscans are one of the best-known groups of invertebrates in the Gulf of Cal i fornia. O f more than 3,300 species found in the Panamic region, a majority occurs in the Gulf of California (Houston, 1980). In the Gulf, mollusks have exploited nearly every conceivable habitat from the intertidal zone to several thousand feet (Kerstitch, 1989). This is in part to the unique structure of the Gulf, which allows changes in the surface water temperature and salinity to vary from the head to the mouth o f the gulf. In the northern gulf where evaporation exceeds fresh water influx, salinities vary from 35.0% <> - 35.8%o and temperatures range 15°C between seasons (Roden, 1964). The southern gulf, however, has mixing with the Pacific Ocean which influences the water’s characteristics forming salinities ranging from 34.6%o - 35%o and water surface temperatures ranging 9°C between seasons (Roden, 1964). Because of these oceanographic differences the Molluscan assemblages differ from the northern gulf to the southern gulf (Keen, 1958; Durham and Allison, 1960). Cenozoic molluscans in the Gulf of California are a mix between Pacific- Panamic and Tertiary Caribbean taxa or their descendants and not from the Indo- Pacific (Sm ith, 1994). The appearance of molluscan fauna in the Gulf of California fossil record began by the Tertiary 12 to 13 Ma in age (; Smith, 1989; Smith, 1994). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37 These marine assemblages included Caribbean species such as Aequipecten muscosus, which is now extinct in the Pacific but still lives in the Caribbean (Smith, 1994). Both early late Miocene and Pliocene mollusks have mixed affinities with Caribbean and endemic species from the Gulf of California (Durham and Allison, 1960; Smith, 1989; Smith, 1994). During the Pleistocene and today many species living in the tropical eastern Pacific have evolved only slightly from their Miocene ancestors such that they are very similar to their Caribbean forms (Durham and Allison, 1960; Smith, 1994). The species affinity between the eastern Pacific and the Caribbean is believed to be from faunal interchange before the formation o f the Isthmus of Panama (Darwin, 1842; Durham and Al lison, 1960; Glynn and Wellington, 1983; Smith, 1989; Grigg and Hey, 1992; Smith, 1994; Cortez, 1997; Glynn and Ault, 2000; Spalding et al., 2001). The most commonly found Molluscan classes found in the Las Animas Pleistocene deposits are Pelecypoda (Bivalvia, Lamellibranchiata) and Gastropoda. Some M olluscan fossils are from the Scaphopoda class, but not in the quantities of the other two classes. Pelecypoda or bivalves have shells composed o f two valves that surround the organism ’s body. The valves are attached together by an articulated hinge held by a tough ligament. Bivalves also use two strong adductor muscles to prevent the valves from gaping. These species can be found living burrowed in sand or mud, attached to rocks or on top of the substrate; some species have also been known to burrow into rock or wood. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38 Gastropoda are the largest class of mollusca (Houston, 1980; Bieler, 1992). Most species have a coiled shell, although some have no coils or no shells. These species are usually found on top o f the substrate or attached to rocks or other shells. There are several nearshore environments in the Gulf that Mollusca abound. These environments are rocky shores, sandy beaches, tidal flats and mangroves. As stated earlier, rocky shores are not only the most common nearshore environment in the G u lf but also have the most variety in Molluscan life, Molluscans are found anywhere among the rocks, either attached (Coilisella sp., Ostrea sp., Spondylus sp., Pinctada mazatlantica), underneath {Cardita gray i, Diodor a inaequalis, Lima up.), or inbetween in crevices (Cypraea annettae, Turbo fluctuosis). They are also found in every tidal zone. In sandy beach environments, molluscans are found on top of the substrate (Trigortiocardia biangulata, Anadara sp., Chione undated a, Tivela sp., Argopecten circularis) and burrowed into the substrate (Terebra strigata, Conns dalI) molluscans that like a range in it, as limits or extreme environments. Common molluscans in these environments are Barbatia sp., Trachycardium sp., Chione sp., Tellina sp., Tagehts sp., Architectonia nobilis, and Nassarius sp.. Mangroves with their specialized environments are only found in the southern parts of the Baja California Peninsula. There are many molluscans that can be found in the sediments around the mangroves (Anadara tuberculosa, Chione jiuctifraga, Calliostoma nepheloide), or attached to the mangroves’ roots {Ostrea palmula, Ostrea columbiensis, Mytella guyanensis). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39 Moving away from the shore to nearshore and deeper water are environments such as sandy and mud bottoms, rhodolith beds, and in the case of El Pulmo, coral reefs where molluscans are also found. Many of the molluscans that are found in the sandy beach are also found in deeper waters near the shore (e.g. Trigoniocardia biangulata, Anadara spChione undatella). Other species prefer the deeper waters where the tides do not uncover the bottom (e.g. Lyropecten subnodosus, Ficus ventricosa, Murex tricoronis). As interest in rhodolith beds have increased, the understanding of the Molluscan assemblages associated with them has as well. The studies by Foster et al. (1997), Halfar (1999), and Cintra-Buenrosto et al. (2002) have increased our knowledge of the Molluscan assemblages found in both modern and Pleistocene rhodolith beds. There are two main types of rhodolith beds, tidally controlled and wave controlled. Although many molluscans associated with rhodolith beds can be found in both environments (Barbatia reeve,ana, Anadara multicosta, Lucina sp Codakia distinguenda. Turbo fluctuosus, Polinices sp., Nassarius sp.), others are found in one type or the other. Common molluscans found in wave-driven rhodolith beds are Area sp., Barbatia altemata, Modiolus sp., Chione sp., and Neritafuniculata. In tidally driven rhodolith beds, common molluscans are bivalves Anadara formosa, Pteria sterna mdDivalinga perparvula, and gastropods Tuntella nodulosa, Natica grayi and Cypraea albuginosa. Molluscans are also found in the reefs o f El Pulmo or associated with coral communities. These molluscans include Lithophaga aristata, Spondylus calcifer, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 Collimlla di.sc.ors, Collisella atrata, Neriuifimculata, Muricanthus nigritus, Muricanthus princeps, and Conus princeps. Rhodoliths In the Rancho Las Animas Pleistocene terrace deposits, rhodolith debris and fragments are as common in the sediments as the coral and molluscan fossils. Whereas these fossils were originally disregarded as just algal debris, further studies o f living rhodoliths have brought to light their usefulness in paieoenvironmental interpretations (Scoflin et al., 1985; Steneck, 1986; Foster el a l, 1997; Basso, 1998; Halfar 1999; Foster, 2001). Living rhodoliths beds are common and widely distributed in the Gulf (Steneck, 1986; Foster, 2001). They are found from the low intertidal zone to depths o f 150 m, where light is strong enough for growth and water movement is strong enough to inhibit burial by sediments. These beds are considered communities and are often found with free-living corals (coralliths - nonattached corals) and free-living populations of other invertebrates that normally grow attached (Foster, 2001). Rhodolith beds are considered "habitat modifiers" or "bioengineers" due to their rigid structural complexity, which provide stable microhabitats for other organisms (Foster, 2001). Rhodoliths (Corailinales, Rhodophyta) are unattached nongeniculate (i.e. lacking uncalcified joints) coralline algae. These free-living algae can occur at high concentrations over large areas. Differences among scientific disciplines, and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41 the nature of the rhodoliths themsel ves have made it hard to provide a common rhodolith language (Foster, 2001), In nature, free-living, non-geniculated coralline algae come in a variety of sizes and shapes often within the same species leading to the multiple terms for the same thing and making it difficult to identity species. Many scientists use the name "rhodoliths" for free-living structures composed mostly (>50%) o f non-geniculate coralline algae. Some scientists call them "rhodolites" and still others call them "maerls" (Foster, 2001). Many investigators break down non-geniculate coralline algae into groups defined by their shape and structure (growth form) calling small thalli a variety o f names (e.g. maerls, marls, nodules) and only the larger rounded forms rhodoliths (Steneck, 1986). This study will follow other authors (Scoffin et a l 1985; Basso, 1998; Foster. 200.1) in calling all free-living, non-geniculate coralline algae as "rhodoliths". As stated above, rhodoliths come in a variety of shapes. In general, the names o f these shapes vary from author to author. Scoffin et al. (1985) break down the rhodolith growth forms into two categories, branching and massive. Branching forms are spikely-branched spheroidal structures with initial growth close to the center o f the rhodolith. Massive forms are encrustations mainly on pebble-sized nuclei. Steneck (1986) used three terms to describe rhodolith morphology: marl, nodules, and rhodoliths. Marls are loose lying branches of a single species. Nodules are more densely branched, spherical-to-ellipsoid coralline algae, and rhodoliths are thick coatings of 50% or more coralline growing on a substratum other than the coralline itself. Of Steneck’s three terms, marls became the most Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 42 confusing because it was a term used for calcareous sediments. Basso (1998) also used three growth forms, however, the mimes are greatly different from Steneck's (1986). Unattached branches include all shapes and forms of mainly branched specimen. Pralines are small, roundish, monospecific rhodoliths with tubercular protuberances or branches. Box work rhodoliths are larger rhodoliths with, more or less irregularly ellipsoidal shape and have vascular, "box.wo.rk" structure. Woelkerling (1.993), Foster et al. (1997), and Foster (2001) use three different morphological terms: fraticose, foliose, and lumpy. Differences in morphology are due to environment and not necessarily to different species (Scoffin et al., 1985; Steneck, 1986; Foster et a l 1997; Basso, 1998; Foster, 2001), making rhodoliths a useful tool in ecological and paleoecological interpretations. Because of its calcified cell walls, heavy fixation to the substrate, as well as intra- and extraskeletal cementation, coralline algae are able to withstand high wave energy (Rasser and Riegl, 2002). Rhodolith assemblages record information on depth, geography, temperature and prevailing hydraulic energy (Cintra-Buenrostro et al., 2002). Rhodoliths form by periodic overturning either by water action or the activity of organisms (e.g. bioturbation) (Steneck, 1986). The shape and size depends on the frequency of overturns. Encrusting, flattened, irregular or "box-work" structures form under the relatively quiet conditions of deeper waters with less wave and current action (Scoffm et al., 1985; Steneck, 1986; Basso, 1998), Infrequent overturning leads to a nonspherical form and partial burial. M arls and strongly branched rhodoliths are found in very shallow zones that have Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43 frequent but not intense wave action (Steneck, 1986). The highly spherical nodule or praline shaped, rhodoliths are more likely to be found in more intense wave action areas where frequent overturning induces the spherical shape (Steneck, 1986; Basso, 1998). It is common to find both the branching/marls with the nodule/praline rhodoliths. W oelkerling's (1993) classifications of rhodolith morphology are similar. Fruticose and fotiose forms are found together in beds exposed to moderate wave action and in current beds and the lumpy shapes are only found in wave-exposed beds (Foster et al., 1997). Foster et al.'s (1997) studies also found size to be controlled in part by depth. The largest individuals were found in the shallowest wave beds whereas the smallest were found in the deeper current beds. They also determined that irregular shapes increased with depth and were more common in current affected beds. Spherical rhodoliths were found at all depths within the wave dominated beds. Branch density was another characteristic Foster et al. (1997) observed. Branch density was highest in the upper to middle of the wave beds whereas branch densities in current beds were the lowest. All these studies lead to a common three-part framework for ecological interpretations. The first part, shape, is mainly determined by water motion. Irregular shape rhodoliths are found in more quiet waters while the more spherical rhodoliths are found in more intense waters. Branch density is the second part, the higher the branch density the more intense the water (e.g., wave beds). Rhodoliths with low er branch density form in quiet waters. Size is the last part, the largest Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44 rhodoliths are found in the shallowest waters where there is intense wave action, while the smallest rhodoliths are found in quiet waters. in the G ulf of California, modem and Pliocene/Pleistocene rhodolith beds are very common (Foster et al., 1991; Foster, 2001; Cintra-Buenrostro et al., 2002). All of the forms o f rhodoliths in the Gulf of California except the lumpy form come from the coralline alga species Lithothamnmm margaritae (Hariot) Heydrich (Halfar, 1999). The lumpy rhodolith forms are derived from the species Lithothamnium crassiusculum (Foslie) Mason (Halfar, 1999). Modern rhodolith beds in the G ulf o f California are found in two main environments; gently sloping, subtidal soft bottoms with moderate wave action, and relatively level bottoms in channels with tidal currents (Cintra-Buenrostro et al., 2002). Examples of rhodolith beds of the Gulf of California can be found in many locations along the coastline. Two such localities are near the Isla El Requeson in Bahia Concepcion, and in the La Paz area (Halfar, 1.999; Halfar et al., 2001; Forrest et al., 2002). At the Isla E l Requeson, rhodolith beds are composed o f free-living nongeniculate coralline algae forming elongated beds parallel to the coastline. These rhodolith beds are restricted to water depths of 5 15 m . and are not stationary. Forrest et al. (2002) believe that these beds migrate in the direction o f littoral current flow. In the La P az area, rhodoliths can reach the size of 13 cm and are usually round or ellipsoidal in shape (Halfar, 1999). O f the rhodolith shapes described by Foster et al. (1997), fructiose is the most abundant found, covering entire areas of the sea floor in th e Canal de San Lorenze (Halfar, 1999; Halfar et al., 2001). This large Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 45 rhodolith bioherrn is found in -13 m of water and rises several meters from the canal floor. According to Halfar (1999), rhodoliths in the La Paz area can also be found in dredged samples taken from the middle shelf to water depths of 60 m (maeri types are the only rhodolith shape found at these deeper depths). The Pleistocene Gulf Dating of corals found in the Rancho Las Animas area places the terrace deposits at approximately 120 - 145 kya. These ages correspond with the late Pleistocene specifically during the last interglacial (Eemian), and marine isotopic stage 5e. It is believed that Substage 5e was the last time that the volume of ice on earth w as as small as it is today (Shackleton, 1969; CLIMAP, 1984; Ashley et a l, 1987; Sirkin et al., 1990; Szabo et a l, 1991; Gallup et a l, 1994; Johnson and Libbey, 1995; Stirling et a l, 1995; Neumann and Hearty, 1996; Ortleib, 1991; McCulloch and Esat, 2000; Kukla et a l, 2002). This time period also corresponds with an overall raise in sea level and surface water temperatures. The rise in sea level varies from a couple of meters to over two hundred meters depending on the presence and rate of uplift (Chappell, 1974; Kaufman, 1981; Ashley et al., 1987; Ortieb, 1991; Woodroffe et a l, 1991; Gallup et a l, 1994; Blanchon and Shaw, 1995; Neumann and Hearty, 1996; Stirling et a l, 1998; McCulloch and Esat, 2000; Muhs e t a l, 2002). The sea surface temperatures also rose a couple degrees (1 - 3°C) around this time period (Stirling et a l, 1995; Kukla et a l, 2002). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46 Because of all these changes in the sea level and temperatures during the late Pleistocene it is important to understand what is happening. Since the Rancho Las Animas area is present in the Gulf of Cali fornia it is also important to try to understand how these fluctuations (e.g., sea level) have effected the Gulf and how changes may have influenced paleoenvironments and other terrace deposits in the Gulf as well. Pleistocene Climate Substage 5e During the last interglacial epoch about 80,000 to 130,000 years ago, sea level stood higher than at any time in the past 350,000 years (Shackleton, 1969; CLIMAP, 1984; Ashley et al., 1987; Sirkin et a l , 1990; Szabo et a l, 1991; Gallup et a l, 1994; Johnson and Libbey, 1995; Stirling et a l, 1995; Neumann and Hearty, 1996; Ortleib, 1991; McCulloch and Esat, 2000; Kukla et a l, 2002). This accounting of sea-level changes is based on fluctuations in oxygen isotopic ratios from U pper Pleistocene deep-sea cores. Typically, oxygen isotope Substage 5e emerges as the last time the isotopic values (planktonic foraminifera 1 - - l%o, benthic foraminfera 4 - 3%o) were as light as they are today (surface water ~0%<.) (Cronin, 1999; Shackleton et a l, 2002). Originally, oxygen isotopic records indicated relatively little structure within interglacial isotopic stage 5, but later work show ed that there were major positive isotopic excursions during Substages 5d and 5b with 5c and 5a never returning to the extremely light Sl80 values of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 ? Substage 5e (Shackleton, 1969). Oxygen, isotopic Substage 5e is thus defined as the peak of the last interglacial; the last time there was as little ice as today. Because of the decrease in the ice volume, these events represent sea-level changes as well. As ice volume decreases, sea level rises. However, the exact amount of sea-level increase is controversial because o f the problem o f separating local tectonic changes from changes due to eustasy. Around the world, Pleistocene terraces (MIS 5e stand), have different heights, ranging from + 6 m in the Bahamas (Neumann and Hearty, 1996) to +30 m in the central Gulf o f California (Ortleib, 1991). The difficulty in calibrating sea-level change along a coastal region is determining which part is eustatic sea-level change (global) and which part is relative sea-level change (e.g. regional - subsidence, uplift). Both of which need to be determined in order to interpret the actual history of sea-level change of an area. Global ice volume gradually decreased from a maximum 135,000 to 138,000 yr. ago to its minimum at about 125,000 yr. ago (Kukla et a l, 2002). Milankovich cycles also suggest a peak in summer solar insolation between 126 128 ka (Stirling et ah, 1995). Temperatures calculated from Vostok ice cores in the Antarctic increased several millennia before the glacial ice-volume minimum (Kukla e t al., 2002). Surface waters of both the western and eastern tropical Pacific and groundwater along the western margin o f the United States (e.g. Devils Hole maxima at 135 ka) also became warmer before the ice-volume minimum (Stirling et al., 1995; Kukla et al., 2002). Beginning about 130,000 yr, ago, interglacial Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 eustatic sea level rose to present sea level and continued to rise until about 125, 000 yr. ago. Pleistocene G ulf Sea Level There have been numerous studies o f Pleistocene terraces on both the Pacific side and the Gulf side of the Baja Peninsula. Along the east coast of Baja California, the Pleistocene shoreline (substages 5a, 5c, and/or 5e) is generally well identified although elevations differ (Ortlieb, 1991). The main last interglacial (IS 5e) shoreline was at +6 to +11 m above present-day sea level along the coast of Northern Baja California. In the La Refornia-Santa Rosalia area (which is an active volcano), the shoreline is elevated up to +25 to +30 m. Between Chivato Peninsula and the Loreto-lsla del Carmen area, the interpreted IS 5e shoreline is at elevations o f +9 to +13 m. There is very little information about the coast segment between Ligui and Bahia de La Paz where the Las Animas area is located, but the area of Punta San Telmo suggests a late Pleistocene high seastand at less than +10 m. Sout heast of Bahia de La Paz, the last interglacial shoreline was at +6 to +9m, and along the southern extremity of Baja Cali fornia, the shoreline appears to be about +6 m (Ortieb, 1991). The differences between high stand levels along the eastern B aja coastline are believed to be the result o f regional uplift (Ortieb, 1991). It is unclear in as to how much of these variations in Pleistocene sea level are due to eustatic sea-level change or to subsidence and uplift. Preliminary data suggest some relative sea-level change has occurred in the Las Animas area, but the amount Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49 is poorly documented and understanding these highstand differences will help to elucidate the neotectonics of the Eastern Baja coastline. Pleistocene Gulf Terraces T he Pleistocene was a time o f great upheaval in the eastern Pacific . Changes in sea level altered available area for reef development, because the continental shelf is narrow and the slope steep (Cortez, 1997). Ecologically, Pleistocene faunal assemblages from Pacific Baja California and Northern and Central eastern Baja fall in two categories, southern and northern extraprovincinal species ( Valentine, 1980; Valentine, 1989; Roy et al., 1995 ). These are termed thermally anomalous assemblages because they contain co-occurring species that today inhabit distinct climatic regimes and may be thriving due to upwelling. Whether or not the southern area o f the peninsula contains thermally anomalous assemblages is not yet known. Faunas from California Province region terraces deposited during substage 5c contain no more than 3% extinct forms (Valentine and Jablonski, 1991). Also, all intertidal species that are common or of ecological importance in present-day communities are found in the California Pleistocene (Valentine, 1989; Smith, 1991, 1994). Many studies in the Gulf done on late Pleistocene rocky shores (Valentine, 1960; Valentine, 1980; Johnson and Libbey, 1997; Libbey and Johnson, 1997; Johnson and Ledesma-Vazquez, 1999) indicate that the faunal assemblages are similar to those in other modern rocky shores with only a few extinct faunas. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50 Using raw species richness and ratified species richness (from rarefaction analyses) of both modern and Pleistocene (IS 5e) marine molluscan assemblages from the G ulf Cintra-Buenrostro et al. (2002) tested the ideas indicated by those from earlier studies. From their analyses, Cintra-Buenrostro et al. determined that although some taxonomic composition and species richness have changed overtime, there is no evidence o f wholesale replacement or reorganization of molluscan assemblages between IS 5e and the present. In the Gulf o f California today , Pocillopora spp. are only found in the southernmost areas. During the late Pleistocene, however, bioherms of Pocillopora spp. lived as far north as Carmen Island (Durham, 1950; Johnson and Libbey, 1997). It is believed that the absence of these corals in the Gulf today is due to three factors; the latitudinal ly confined, tropical waters, the absence of suitable substrate, and the presence o f large, freshwater rivers along the eastern shores. It is interesting that none of the Pleistocene corals in the Gulf have become extinct, but they all live further south (Brusca, 1980). The presence of large communities of corals (i.e., Pocillopora spp., and Porites panamensis) in the Gulf of California during the Pleistocene, when they were absent throughout the rest of the American Pacific coast, suggests that the Gulf m ay have been a refuge zone for warm-water faunas (Reyes-Bonilla, 1992; 1993), or that the emerging arid Baja peninsula may have preserved the coral- bearing terraces where the tropical precipitation of the central American Pacific could not (Glynn and Wellington, 1983). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51 Pleistocene terraces can be found in many localities along the eastern coast of the Gulf, While almost all of these deposits are wave-cut cliff lacings, they very in size and preservation. These deposits also represent several different paleoenvironments or facies including rocky shores at Cabo Pulmo (Squires, 1959) and Bahia San Antonio (Johnson and Ledesma-Vaquez, 1999), coral communities and thickets o f Porites panamemis at San Telmo (Squires, 1959; Ransom, 2000), Coronados Island (Squires, 1959), Marquer Bay (Squires, 1959), Punta Bajo (Ransom, 2000: Fenburg and Goodwin, 2002), Punta Chivato (Ransom, 2000), and Isla Espiritu Santos (Halfar et a l 2001), rhodolith beds at Isla Espiritu Santos (Halfar, 1999; Halfar et a l 2001), Punta Chivato (Ransom, 2000; Cintra- Buenrostro et a l, 2002) and Punta Galeras-Canal de San Lorenzo (Cintra- Buenrostro et a l, 2002), oyster beds at Cabo Pulmo and San Telmo (Squires, 1959), and sandy facies which are very common and found at most of the localities previously listed. Descriptions o f a few of these localities are given below. Cabo Pulmo Along the narrow beach of Pulmo Bay is a sea cliff varying in height from 20 to 40 ft. (Squires, 1959). The cliff extends continuously to Los Frailes, with occasional outcroppings of Pleistocene sediments. The base o f the outcrops is a pink granite, which is exposed from the below the tide line to about 2 meters, above the m ean tide level. (Overlying the granite by unconformity is a basal conglomerate composed of well-rounded boulders of igneous rocks of di verse types, cemented by Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. a calcareous shell breccia containing fossils. Fossils found in the basal conglomerate include Porites sp., Pocillopora verrucosa, Ostrea chiUensis, and Spondy It is princeps (Squires, 1959), The basal conglomerate is approximately 1.5 m. Above the conglomerates is another unconformity covered with about a meter of pebble conglomerates. Overlying the pebble conglomerate is 3 m o f finely bedded sediments fining upwards. These sediments are marine and contain fragmentary shells and fossils, but no corals. Fossils found in this upper section are Glycymeris maculata, Chione califomiensis, Cardium biangulatum, Lucina sp., and Oliva sp. (Squires, 1959). The uppermost section contains cross-bedded sands and no fossils. San Telmo North of San Carlos Bay and j ust south of San Telmo Point is a series of exposures of a Pleistocene coral bioherm (Squires, 1959; Ransom, 2000). At the westernmost portion of the bay, the basal Pleistocene section is where oyster patches and aggregations are found. Just above the oysters are 2 - 3 m of pinnacled masses o f Porites. The coral section is capped with 3 - 5 m of alluvian gravel conglomerates containing no fossils. Fossils found in the reef section include 33 gastropods species, 32 Pelecypoda species, and 4 coral species (Pocillopora verrucosa, Porites panamensis, Porites sverdrupi, and Porites sp.). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53 Punta Bajo Located approximately 400 km north of Loreto, there is a series o f cliffs along the beach with Porites panamensis corals (Ransom, 2000; Fenburg and Goodwin, 2002), Several sea levels are represented here with some at present sea level and some elevated. Mayer et al. (2002) believe these levels to represent MIS 5a and 5e, Beds believed to be 5e contain corals that are one to two meters in height. These corals heads grow up to 1.5 meters in height. Capping the corals beds are fossiliferous sands. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 54 CHAPTER. 2 Methods Field M ethods Sampling Fossils for the statistical analysis were collected by one o f two methods: bulk samples and 1 ft sq. area analysis. Bulk samples were obtained in a 5" x 10" HUBCO (Hutchinson Bag Corporation) sand sample bags. The bulk samples consisted of sediments and/or any fossils found within those sediments. Samples were weighed for total weight, and fossils were identified and counted in the laboratory. Terrace Location and Elevations Terrace sites were determined using both aerial photomaps and global positioning (GPS). Aerial photographic maps taken at two different times (i.e. before th e road was constructed (1980’s) and after the creation o f the road) were used in the field for identifying land formations and locations. Global positioning was determined with a Gannin GPS 1 .2 hand held unit. Terrace locations of interest were m arked in the GSP unit and latitude and longitudes calculated. Appendix A contains latitude and longitude readings for all sites. Sites were then named using an easy identification numbering system of D#S#, for example D2S.1.2 would mean Day 2 a t Site 12. The GPS unit’s map mode was also used to determine terrace outlines and distances between sites. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Terrace elevations were determined using hand held altimeters and stratigraphic measurements. Altimeters were frequently zeroed at the beach and wandering errors were as much as + 4 meters. Stratigraphic sections were measured using measuring tape. Both stratigraphic measurements and altimeters were used together to determine terrace heights and altimeter errors. L aboratory M ethods Fossil Identification All fossils were identified to genus and/or species level based on Durham (1950), Keen (1958), Brusca (1980), and Kerstitch (1989). Gastropods were cross- referenced with those found in the Los Angles County Museum of Natural Arts collections. References were also used to denote species habitat and biogeographical range. The number of species and specimens were counted and tabulated on an Excel sheet. Cluster Analyses Total fossil counts and presence/absence counts were entered into spreadsheets. These spreadsheets consisted of 52 samples collected from various sites, with either 177 different fossil species counts or 89 genera. The spreadsheets were then entered into a SYSTAT 9 program and total fossil counts standardized. Euclidean distances were calculated for all samples and sites. Cluster method analysis, using clusters of single, average, and complete linkages were performed Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56 for Species and Genus levels. Both R* and Q-mode of cluster analyses were used on Species and Genera level o f organisms to determine similarities between fossil assemblages and sites. Age Dating T o determine the age and duration o f the Rancho Las Animas sequence, specimens o f the coral Porites panamensis were selected for U-series TIMS analysis. Heads of P. panamensis in growth position were collected intact from the top, middle and base of the Large Corals facies and smaller, peneiksize specimens from the smaller Porites facies resting on the terrace surface. Selected pieces from within the individual coral heads were cut into 0.5 cm size pieces, removing the outer surface. They were then cleaned mechanically, crushed to mm size pieces, cleaned again, washed in deionized water, and both X- rayed and stained with cobalt nitrate for aragonite content. X-ray diffraction of the powered samples of the corals indicated 95-97% aragonite. Coral fragments were examined by Scanning Electron Microscopy (SEM) for crystal overgrowth or recrystalization to calcite and no crystal modification was found (R. Douglas, per comm., 2002). Analytical methods and procedures, isotopie ratio measurements and Ik series systematics for the age determinations were carried out at the Department of Geological Sciences at the University of Texas, Austin. U and Th isotopic analyses Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57 were done using a Finnigan-MAT 261 thermal-ionization mass spectrometer (TIMS), Age dating was determined using modifications o f those previously reported in Musgrove et al, (2001), Grain Size Analyses Bulk samples were collected at several locations in all three- terrace segments. Sediment samples were analyzed for mean grain size phi, standard deviation, skewness, content, and shape. Samples were analyzed using a sieve shaker with sieve sizes 1 mm, 0.5 mm, 0.25 mm, 0.125 mm, and 0.05 mm. All samples were placed into preweighed containers and then reweighed. Container weights were then subtracted from the total weight to produce sediment weight values for each sieve size. These weights were then recorded and used for size frequency and cumulative frequency analyses (Appendices F and G). The moments of each sample were calculated using a moment calculation spreadsheet made by Dr. Donn Gorsline, at the Earth Science Department, University of Southern California. Two sets of moment calculations were preformed for each sample: Total sediment and small size grain fractionations. Small grain size fractionations were preformed to eliminate any skewing due to fossils. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58 CHAPTER 3 Fossil Analyses Fossil analyses of the Rancho Las Animas Pleistocene deposits consists of identification of the Pleistocene fossils, identification and interpretation of the facies within the Pleistocene unit, and statistical analyses o f the fossils and Rancho Las animas sites. Fossil Identification Identification of fossils, using Durham (1950), Keen (1958), Brusca (1980), and Kerstitch (1989) references, was entered into a spreadsheet. These results are in Appendix B, with genera and species grouped by families. Species habitat and biogeograpbical range were determined from published reports. These results are in Appendix C. T errace Litho- and Biofacies A marine eustatic cycle and several, facies are preserved in the terrace deposits. These deposits range from beach gravels to corals, and vary in thickness from se veral centimeters to over 10 meters. The following facies were recognized based on the litho facies and fossil biotas exposed in the three terrace segments of the Las Animas area. The same facies are recognized in all the terrace deposits, but they vary in exposure, thickness and completeness in the di fferent terraces. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59 C'etro Colorado Member Underlying the Pleistocene terrace is a progradationai sequence of fine grained elastic sediments, followed by fine- and coarse-grained sandstones (Figure 12). The Cerro Colorado Member is discussed in Chapter 1. Basal Conglomerate Unit The Pleistocene marine sequence begins with a sandy conglomerate of rounded to angular pebbles, cobbles and boulders o f Miocene volcanics and reworked Cerro Colorado and fossil fragments in a coarse-grained sand matrix (Figure 13). This unit varies in thickness and extent, from a thin unit (<20 cm thick) with pebbles and small cobbles where it rests directly upon the eroded terrace surface to thicknesses up to several meters in channels and depressions. Small oysters (Ostrea palmula) are commonly found cemented to the cobbles and boulders. In depressions, the basal beds are ungraded with, matrix-supported larger clasts, suggesting large storm deposits. Beds either indicate rocky shore intertidal, nearshore conglomerates, channel gravels or stomi-deposits with gravel/boulders, all of which suggest strong currents to transport and deposit the large grain-sized boulders and gravel. Where oysters a re presents, water depth was no more than a few meters. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 60 Figure 12, Green Beds of Cerro Colorado Member Overlain by the White Pleistocene Deposits at Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 13. Conglomerate Facies. Picture Taken at Site D4S2 in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 62 Fossilijet’ ous and Reworked Cerro Colorado Sand Unit Fine to medium grained sand, reworked from the underlying Cerro Colorado Member containing Pleistocene fossils and rhodoliths, is found with conglomerates at the base o f the terrace sequence (Figure 14). This unit is generally no more than 30 cm in thickness. Common fossils are the molluscs Chione sp., Pectens, Serpulorbis spOliva sp., the echinoderai Encope sp., and burrows a couple centimeters in diameters and several centimeters in length are similar to burrows found in shallow sandy bottom environments. Some units are filled with fossil and algal debris suggesting a storm. This unit may be the finer- grained end part of the conglomerate unit. Large Coral Unit. The most distinctive feature of the terrace deposits, these beds consist of densely packed, bouquet-shaped coral heads o f Pontes panamensis in growth position, enclosed in an uncemented matrix of bioclastic sand, rhodolith debris and molluscan shells (Figure 15). In growth position, the coral heads are typically 20- 50 cm in height, and range to over 160 cm long in the lowest part of the unit. The coral heads are arranged in poorly defined beds, 1-3 m thick, separated by thin layers o f sand or coral rubble. In the channels and depressions, the P. panamensis beds attain a thickness up to 8 m, and rest directly on coarse bioclastic sand, oyster debris and sparse cobbles. Small irregular beds o f toppled and broken coral heads occur in places suggesting storm deposits. Common fossils found in these deposits Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63 Figure 14. Fossiliferous and Reworked Cerro Colorado Member Sands. Picture Taken a t Site D1S13 in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 15. Large Corals Facies. Picture Taken at Site D6S12 in Km 26 Terrace Segment. . Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 65 include Barhaiia reeveanna, Anadara multicosta, Plnctada mazatlantica, Ostrea palmula, and echinoid spines. In life, the corals formed large patches on the sea floor, mainly concentrated in the central part; of the ancient embayment. There the corals first colonized pre existing channels and depressions in the existing topography, and then spread to the terraced surface o f the Cerro Colorado with the rise in sea level. While the coral colonies may have modified wave patterns, they do not appear to have been reefs in the classic sense. The corals form open-framework structures, which are not cemented and unlikely to have been wave-breaking features, although the platy- morphology of large specimens at the base of the unit (Figure 16) suggests wave- action or strong currents. Traditionally, there are four requirements needed for a structure or community to be considered a reef (Glynn and Wellington, 1.983; Morelock, 2000; Spalding et al., 2001). One, the structure must be constructed of material of biological origin. Second, the structure must be composed either of interlocked and in situ framework elements or reworked framework elements bound together by secondary encrustation or cementation. Third, it must stand topographically above the surrounding seafloor and exert local control on oceanographic processes. Lastly, the majority of the framework elements must be formed in an environment similar to the one in which they were deposited. Although the corals at the Las Animas site have a loose interlocking framework, they form an open framework infilled with a sandy matrix of nearshore siliclastic sands and reworked coral debris (Figure 17). There is no cementation o f the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 66 Figure 16. Platy Coral Morphology Seen Growing Over Branching Morphology. Picture TAken at Site D6S8 in Km 26 Terracde Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67 Figure 17. Sandy Matrix of Large Corals Seen Washed Away in Talus. Picture Taken at Site D 2S9 in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. framework elements, 'The corals may have exerted some control on the local wave and tides, bat it does not appear to have been extensive. Because these coral bioherms do not fit the classical requirements o f a reef and are in-tilled with nearshore sediments, these structures are best described as coral mounds or thickets. In a few locations, the sediments, corals and molluscan fossils in the Large Corals facies are stained a green color by material remobilized from the underlying Cerro Colorado Member. The corals are typically weathered, coated with a dark- colored green and poorly preserved. The green discoloration is the mineral celadonite, which gives the underlying Cerro Colorado Member its distinctive green color (Gidde, 1992). Scanning Electron Microscopy of coral fragments from these areas have found that it is common to find P. panamensis skeletal material coated in silica. How both the green celadonite and the silica coating were deposited is unclear. However, many of these sites are in the close vicinity to small normal faults, and it may be possible that ancient hydrothermal vents were located along the faults. These vent types are known in the modern Gulf of California such as in Bahia Concepcion (Forrest et al., 2002; Greene and Forrest, 2002). It is possible that these vents may have played some part in the remobilization of the celadonite into the overlying corals, and also in the silica coating of the skeletal material. The paleodepth of these bioherms are between 1 to 10 meters. Even though P. panamensis is not found today to the extent it was in the Pleistocene, modern P. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69 panamensis is found between 1 to 10 meters within the Gulf. Common fossils found in these deposits such as Pinctada mazatkmtica, Ostrea palmula (both of which can be found with both valves), and eehmoid spines can be found attached to rocks and/or corals in intertidal to subtidal zones. Other fossils commonly found in this unit such as Barbatia reeveanna and Anadara multicosta are typically found on sandy bottoms in shallow waters and rhodolith beds. This suggests that many of the fossils found in the sandy matrix, around the corals are transported and deposited with the sand and are not in situ. Pontes, Mollusean and Rhodolith Sandy Marls Unit These light gray-buff colored, coarse to medium grained shelly sands contain a combination of abundant small Poritespanamensis, isolated oyster mounds, a diverse mollusean assemblage, and rhodolitlis, which cover the terraces and Large Coral Units. In the terrace deposits near the present coast, the sands grade upwards into a coquina with pebbles. Because this unit contains such a variety o f different types of fossils, three distinct subfacies can be detected: "Pencil” Porites and Mollusean Sandy Marls, "Finger" Porites, Mollusean and Rhodolith Sandy Marls, and Rhodolith and Mollusean Marls. These subfacies have the sam e typical mollusean assemblage with common Gastropods, including Acmaea sp., Architectonia nobilis, Coliisella strongiana, Nassarius tiarula, Oliva sp., Terebra sp., and Turritella sp. together with the bivalves Chama sp., Chione sp., Lucina cancellaria, Megapitaria, PJicalula inezana, and Spondylusprinceps. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70 The differences between these three subfacies lie in the absence and/or presence of the small Porites corals and the rhodoliths. ''Pencil" Ponies and Mollusean Sandy Marls I n this subfaeies, small “penci l” sized Porites panamensis are found and rhodoliths are absent. These are small forms of branching P. panamensis, with branches 0.5 to 2 cm in diameter and heads 10 to 20 cm high form beds tip to 25 cm thick (Figure 18). These deposits represent paleoenvironments o f intertidal to shallow waters. Many o f the fossils found in these beds are from either rocky shore and/or sandy habitats. It is possible that this facies represents a sandy bottom area with rocks or debris present. "Finger" Porites. Mollusean and Rhodolith Sandy Marls These units are very similar to the "Pencil" Porites and Mollusean Sandy Marls in fossil assemblages, thickness and extent. The differences are in two general features, the shape of the corals and the presence of rhodoliths (Figure 19). The Porites panamensis found in these units are thicker and knobbier than those found in the "Pencil” Porites and Mollusean Sandy Marls facies. Rhodoliths are Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 18. "Pencil" Porites and Mollusean Sandy Marls Subfacies. Picture Taken at Site D12S6 in Dune Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 19. Porites, Mollusean and Rhodolithic Sandy Marls Facies. Picture Taken at Site D i S3 in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 either knobby or branching (i.e. lumpy and fruticose respectively according to Foster et a l 1997). This unit indicates a simitar paleoenvironment to the “Pencil” 'Porites and Mollusean Sandy Marls unit. The main different between the two is the presence of the rhodoliths, specifically the fruticose and lumpy morphologies. These morphologies are prevalent in areas where moderate current and wave action are occurring. Adding to the rhodoliths, the th icker form o f Porites panamensis present indicates that, although these units were deposited at similar depths, they were deposited in a higher current or wave energy area. Rhodolith and Mollusean. Marls As with the "Pencil" Porites and Mollusean Sandy Marls and the "Finger" Porites, Mollusean and Rhodolith Sandy Marls, these units are very similar in grain size and color, fossil assemblage, and unit thickness. The differences are the presence of rhodoliths and the absence of corals (Figure 20). The absence of the corals and the presence of the rhodoliths may indicate that the environment may have had too much o f a sediment flux by way of strong currents, there may have not been any place for the corals to attach themselves or the rhodoliths and corals may be competing for space. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 74 Figure 20, Rhodoliths and Mollusean Sandy Marls Subfacies. Picture Taken at Site D5S1 i in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75 Fossiliferous Sands Unit Exposed in a few places inland, beneath the alluvial gravels and resting on the terraces of eroded Cerro Colorado to the south, are sands that were deposited at the edge of the ancient embayment. The sands are uncemented, medium to fine grained with echinoderms (Encope sp.), burrows and common bivalves Trigohiocardia biangulita, Anadara multicosta, Cardiia affinis, Codakia sp., Megapitaria sp., Ostrea sp., and Plicatula inezana (Figure 21), Reworked fragments of P. panamensis are common in these sands. The deposits, found at the inner edge of embayment, nearest the rocky shorel ine, are light colored and quartz- rich, whereas the sands to the south are dark-colored and rich in volcanic-derived grains. These units in the terraces to the south are generally found towards the end of the marine sequence. Fossils indicate that paleoenvironments were between intertidal to several meters. Most species, such as Trigoniocardia biangulita, Anadara multicosta, Cardiia affinis, Codakia sp., and Megapitaria sp., prefer tidal flats and sandy bottoms. Another subfacies of the Fossiliferious Sands Unit is the Encope Sands. This subfacies consists of medium to fine-grained sands filled with whole and fragments of Encope sp. and molluscs (Figure 22). Common molluscans found in these sands are Argopecten circularis, Chione califbriensis, Cerithium sp., Semele flavenscens, and Stngilla lentieula. Burrows, commonly found in the sands, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 21. Fossililerous Sands Facies. Taken at Site D6S17 in Km 26 Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 22. Encope Sands Subfacies. Picture Taken at Site D2S9 in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 78 are extensive with several burrows connecting together (possibly the ghost crab and/or Thalassiniodes). Rhodoliths are commonly found in these sands in fruticose forms. This facies represents a sandy nearshore bottom environment from intertidal to less than 20 meters in depth. The presents o f fruticose rhodoliths also implies an area with moderate currents and/or waves. Beach Gravels Unit Capping the terraces are dark-colored rounded pebbly conglomerates with abundant shell fragments (Figure 23). Fossils include mostly broken bivalves (Chione sp., Anadara multicosta and Trigoniocardia biangulita). Rounded basal cobbles are up to 5 cm in diameter. The sandy coarse to medium grained sands are dark-colored and rich in volcanic-derived grains. This facies probably marked the low tidal portion o f the ancient shoreline, with the rounded cobbles and gravels indicating much wave action. Oyster Beds and Mounds Oyster shells and shell fragments, representing a number of different species, are found throughout the Pleistocene sequence. In several facies, cemented oyster shells form mounds and beds, varying from less than a meter to many ten s of meters in size. Oyster beds are interbedded with conglomerates (Figure 24), or form small mounds in the bioclastic sands on top of the terrace Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 23. Beach Gravel Facies. Picture Taken at Site D9S7 in Dune Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 24. Oyster Bed Facies. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81 (Figure 25). This unit is 0.5 to 1.5 m thick beds of Ostma palmula, occurring with abundant Nassanus tiamla, Oliva spicata, Isogonomon chemnizianus and small P. panamensis. All of these species live intertidally to several meters, and all attach to rocks or other hard substrate. Oyster beds and mounds apparently flourished in the vicinity o f what are believed to have been hydrothermal vents along some of the small faults in the area. Small Poeiltopora Thin beds o f small lobed coral lites o f Poeiltopora sp., about the width of a finger and not more than 10-12 cm in length, are found within the Rhodolith and Mollusean Marls (Figure 26). These beds include abundant Petaiconchus sp., Trigoniocardia biangulita and Chione sp.. In other localities, delicately shaped coral lites form at the bottom of the Large Corals facies (Figure 27). These are the only occurrences of Pocillopora sp. (possible P. elegans and/or P. damicornis) in the Pleistocene deposits, although this genus forms most of the coral patches/reefs in the G u lf of California today (Glynn, et a I 1983). Rhodolith Mounds Rhodolith mounds are small, less than one meter in diameter circular, or ovoid formations found at the top of the terrace segments (Figure 28). The rhodoliths are fruticose or lumpy in shape. Fragments of corals (Porites panamensis) and mol tusks are also found among the Rhodoliths. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 82 Figure 25. Oyster Mound at Site D2S4 in Animas North Teneace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 26. Small Pocillopora Facies. Picture Taken at Site D8S3 in Dune Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 27. Arrow Pointing to Small Pocillopora Facies. Picture Taken at Site D3S5 in. Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 28. Picture of a Rhodolith Mounds Taken at Site D IS9 in Animas North Terace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 Storm Layers Storm deposits are common within, overlying units, composed of a few cobbles and boulders suspended in bioclastic rubble o f displaced molluscs, echinoid spines, broken corals and algal debris. These storm deposits are found throughout the terraces, and vary from a few centimeters to almost a meter in thickness. Figures 29 and 30 demonstrate two different storm layers. Figure 29 is a series o f storm beds, alternating layers o f rhodoliths with fine reworked Cerro Colorado Member sands. The storm unit in Figure 30 illustrates the horizontal layers o f broken Pontes panamemis within the Large Corals facies. C luster Analyses Introduction Cluster analysis (CA) refers to a large family of techniques, each of which attempts to organize entities (i.e. sampling units) into discrete classes or groups. This hierarchical method operates on a matrix of similarities, among a set of units and displayed as a dendrogram (Manly, 1986; Digby and Kempton, 1987; M cGarigal et al„ 2000). Methods of describing these clusters start; with the calcul ation of the distances of each individual to all other individuals. Groups are then form ed by a process of agglomeration, in which all objects start by being alone in groups of one. Close groups are then gradually merged, until finally all the individuals are in one single group (Manly, 1986). The two clustering methods used in this experiment are single and complete linkages, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. g? Figure 29. Alternating Layers of Rhodoliths and Fine Sands Storm Layers. Picture Taken at Site D5S14 in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m Figure 30, Horizontal Storm Layer in Large Coral Facies. Picture Taken at Site D2S9 in Animas North Terrace Segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 89 Single linkage or "nearest neighbor" merges individuals o f the closest distances into groups. These groups arc then linked to other individuals or groups in relation to their 'closeness' to each other. Complete linkage or furthest neighbor merges the individuals or groups only if the most distant members of the two groups are close enough. Distances are calculated using Euclidean distances, which are the measure of the dissimilarity (or distance) between two individuals based on the average score on one or more variables. It is the measurement o f the length of a straight line drawn between two individuals in multidimensional space (McGarigal et a i, 2000). The formula for Euclidean distances is: E Djj — sqrt{|L) (X jit - Xjk) } R- and Q-mode cluster analyses were preformed on both total fossil counts and presence/absence counts. R-mode cluster analyses groups species together that are commonly co-occur in samples, and thus defines fossil assemblages. Q-mode cluster analyses group samples together that have similar fossil compositions, defining areas that support similar fauna or biofacies. Total fossil counts were standardized using the formula present in the SYSTAT 9 program. Standardization is where the raw data are transformed into new variables with a mean of zero and standard deviation of one. This is done by subtracting the mean from the raw score values and dividing by the standard deviation. Presence/absence data were Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 calculated by using a simple binary pattern o f l's for the presence of a fossil and 0's for the absence. Because the data in the presence/absence matrices were similar standardization was not needed. Results The best dendrograms for both the R- and Q-mode analyses were chosen based on formation of groups within the clusters. In the R-mode cluster analyses, the best dendrogram is based on for genera presence/absence counts and a complete linkage (Figure 31). Seven distinct groupings are seen in this cluster representing fossil assemblages and habitats. Using the Q-mode cluster analyses, two dendrograms with distinct groupings were produced, one for standardized total fossil genera counts using a complete linkage, and the other for presence/absence genera counts using complete linkage. The first Q-mode cluster analysis produced three groups at the 1.45 distance (Figure 32). The three groups were then broken into sm aller subgroups based on groupings at the 1.4 distance and fossil assemblages. The second Q-mode cluster analysis produced two main groups at a distance of 0.63 (Figure 33). These groups break up into 4 subgroups at a distance of 0.53. Other dendrograms produced for both R~ and Q-mode analyses using other linkages (i.e. single and average), standardized total fossil counts at species level and presence/absence counts at species levels were disregarded because they produced cascading clusters of one sample at a time merging into one main cluster. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91 R-Modc Analyses The R-mode dendrogram of fossil assemblages based on 89 genera yields six clusters (Figure 31). These clusters were determined by the distance at which they formed distinct groupings in the dendrogram (a distance o f 0.53). Group 1 contains five genera, three bival ves Plicatula, Trigoniocardia, and Anadara, one coral PociUopora, and one crustacean Tetraclita. The three bivalves are found in intertidal to shallow water sandy bottom environments, although the last bivalve Anadara is more common in shallow waters. The coral PociUopora and the crustacean Tetraclita are usually found attached to hard substrate so some rocks or stones may have been present With the exception o f Tetraclita all of these organisms live or can live in shallow waters below intertidal. This group represents a shallow water sandy bottom assemblage. Group 2 represents twelve genera including seven gastropods Polinices, Cerithium, Nassarius, Oliva, Stromhus, Terehra, and Architectonia, three bivalves Divalinga, Trachycardium, Tivela, one ahermatypic coral Astrangia, and one echinoderm Encope. All of these genera, with the exception of Astrangia, live in sandy or tidal flat environments. Most are also found in modem rhodolith beds. Astrangia is generally found attached to rocks or shells, so may also be found in this environment. Group 2 represents a sandy or tidal flat environment. Group 3 consists of six genera containing four gastropods Diodora, Serpulorbis, Crucibulum and Turbo, and two bivalves Donax and Cardita, All of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 92 Shallow Water 1 ‘ W f f i Sandy Bottom T rig o o K w r?! Tidal Flats Intertidal Rocky Shore ly c s K f Bam efel ( '.pt,u:a t a j D M S Cofifoa lytjM m s T & n o n u m m x m rm Imv’ i e a r A v i m m Sands and Rocks Rhodolith Beds Venmciiiatm * D ipPlf Auorma f a t i c a K um eiula /V K tChis L t*cm C T jMLum Sand Flat M cW p Rhodolith Beds "Spo|vu.s, T h a u u l w L tos f Rocky with Sands c w a X 1 Mnteua' * o n e p t e n [UCUIUj l W " nmys: fgiiacti# I p p O Q I X D i& a e ttm " Petakpnch Rocks and Sands S f c i __________________SJcw m Common R b o d o r a l i 's 9 * Z b jj I > ~ ... | \ y < 5 - O' Q > % Euclidean Distances Figure 31. Cluster free ofR-Mode Analysis of presence and absence counts of Genera found in Las Animas Pleistocene Deposits. Fossil Assemblages and. Group Numbers are shown on left side of figure. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93 these genera are found interticiaily, either attached to rocks, under rocks or in- between the rocks. This group represents a rocky shore assemblage. Group 4 contains fifty-seven genera, which can be divided into three subgroups at the 0.4 distance. The first subgroup contains thirty four genera, consisting of nineteen bivalves Glycymeris, Pitar, Pinna, Codakia, Mytilidae, Modiolus, Ctena, Dosinia, Nucula, Laevicardium, Corbula, Spengleria, Strigilla, Diplodonta, Anomia, Pecien, Apolymetis, Semele, and Lucina, eleven gastropods /'/za/v, Cypraea, Conns, Muricanthus, Bulla, Acmaea, Vermicularia, Modulus, Natica, Eumetula, and Anachis, one crustacean barnacles, two scaphopods Dentalium and Fustiaria, and one coral Psammocora. The majority of the genera present in this subgroup are found in sandy environments and rhodolith beds. A few genera, such as the gastropods /'/zu/.v and Cypraea and the bivalve Pinna, are found attached or around rocks. The second subgroup consists of five genera including three bivalves Megapitaria, Tagelus, and Tellina, and two gastropods Olivella and Nerita. All the genera found in this subgroup can be found in sandy and tidal flat environments and in modern rhodolith beds. The third subgroup contains eighteen genera representing nine gastropods Murex, Malea, Hipponix, Collisella, Mitra, Credipula, Turriiella, Heliacus, and the family Thaididae, eight bivalves Spomlylm, Lyropecten, Argopecten, Nuculana, Chlamys, Area, Tivela, and fsogonomon, and one echmoderm Diadema. Most of the genera found in this subgroup (e.g. Spondylus, Murex, and Collisella) represent a rocky shore with sand environment. The first two subgroups consist of rhodolith bed assemblages that are Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94 split by those genera found in rocky environments and those found in sandy tidal flat environments. The third subgroup represents a rocky environment assemblage possibly with sand nearby. One last genus is found in the Group 4, which does not lie in any subgroup, the echinoderm Eucidaris possibly indicating a preservation problem. This sea urchin is a rocky shore organism found from extreme low tide to shallow waters, and is commonly found with other rocky shore genera found in the other subgroups. The underlying different between the first two subgroups and the third subgroup is the presence of genera found in rhodolith beds. The presence of rocky habitat genera that are found also in modern rhodolith beds, is probably causing the linkage to the mainly rocky environment assemblage. Group 5 contains four genera including three bivalves Pinctada, Barbatia, and Chama, and one gastropod Petalconchus. All can be found attached to rocks, and m ost can be found in rhodolith beds. Most these organisms (i.e. Barbatia, Chama, and Petalconchus) are found in intertidal to shallow waters while Pinctada is found subtidally. Because of the presence of Pinctada in this group, it is possible that this group represents a shallow water rocky assemblage probably just below the intertidal zone. T he last cluster group 6 includes three genera, Ostrea, Chione, and Porites, and rhodoliths. The organisms in this group are a bit diverse. They live either in rocky environment (i.e. Ostrea, Porites), sandy bottoms or tidal flats (Chione), mangroves (Ostrea) or rhodolith beds (i.e. rhodoliths, Chione). This group Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 95 basically consists o f the most common fossils found in the Las Animas terrace deposits, O M ode Analyses The first Q-mode dendrogram based from 52 samples and standardized genera fossil counts contains three groups (Figure 32). These three groups also form several subgroups at the 1.4 distance. Group 1 contains 25 sites and 5 subgroups. Subgroup I A, formed by three sites, consists of three common genera Murex, Strombus, and Terebra. Both Murex and Strombus are found on and among rocks, while Terebra and Strombus are also (bund in sandy bottom environment. This subgroup probably represents an intertidal to subtidal environment with both rocks and sand. Subgroup IB contains 7 sites, which include the common genera Ostrea, Porites, and Chione. All of these genera are found in rocky environments, and can be found in tidal flat regions such as mangroves. Subgroup 1C consists of 7 sites and two common fossils, the genera Porites and rhodoliths. Both of these fossils are found from the intertidal region to shallow waters. However, Porites are generally found attached to hard substrate such as rocks, while rhodoliths are found in flat sandy areas, so these sites probably represent an environment with shallow' sandy bottom close to a nearby rocky shore. Subgroup ID consists of 5 sites with several common genera, Petalconchus, Barbatia, Ostrea, Diadema, Pinctada, Porites, and Chama. These genera a re all found in rocky bottom environments, although some (i.e. Barbatia Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 Rocks and Sands T < Intertidal tu SuMttoi V r Rocky. Lagowml or Mangrove T60 TO P D Rocks and Sands t o g Sandy Bottom Tidal Flat A Subtidal Sands Figure 32. Cluster Tree of Q-Mode Analysis of Standardized Genera Total Fossil Counts. Group Numbers, Biofacies and Sample Sites are shown on the left of the figure. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97 and Chama) can also be found in sandy bottom environments. The last subgroup IE contains three sites with common generaDiodora, Serpulorbis, and Turbo, All of these common fossi ls can be found on and around rocks, from the intertidal to subtidal zones. In general, Group I, with its five subgroups, indicate a rocky shore/bottom biofacies with some variations towards rocks with sands (subgroup 1A and IC) and tidal fiats/ mangroves {subgroup ID). Group 2 contains 21 sites and 2 subgroups. The first subgroup 2A consists of 15 sites with the common genera Chione. Several other genera and fossils are commonly found between the sites, but with less frequency, rhodoliths, Porites, Cardita, PociUopora, Trigoniocardia, and Barbatia. All of these fossils, except for the corals Porites and PociUopora, can be found in sandy bottom, tidal flats, or rhodolith bed environments. Subgroup 2B contains 6 sites sharing five common genera, Oliva, Nassatius, Chione, Porites, and Tivela. With the exception of Porites, all of these genera are found in sandy or tidal flat environments. Both of the subgroups in group 2 indicate a sandy bottom biofacies, either a sandy beach, a tidal flat and/or rhodolith bed environment. Group 3 contains 6 sites and two subgroups. Subgroup 3 A consists of two sites, which include the common fossils Cntcibulum and Lyropecten. The genera Lyropecten is found in subtidal sands, while Crucihulum can be found in rocks, sands and tidal flats. Subgroup 3B consists o f 4 sites with one genus in common, Encope. The echinoderm Encope is generally found in shallow sand bottoms and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98 tidal flats. In general, Group 3 identifies sites with tidal flat biofacies and possibly deeper waters than those found in group 2. The second Q-mode dendrogram based from presence and absence counts of the genera, contains four groups determined at the 0.53 distance (Figure 33). Group 1 contains four sites with six. common genera, Oliva, Terebra, Nassarius, Anadara, Chione, and Megapitaria. All of these genera are found in sandy bottom and/or tidal flat environments. Some such, as the bivalves Anadara, Chione and Megapitaria are also found in rhodolith beds. Group 2 contains three members that include four common genera, Crucibulum, Strombus, Chione, and Trachycardium. All o f these genera are commonly found in tidal, flats, although Crucibulum are also found on rocks. Group 3 contains 23 sites with five subgroups. Subgroup 3 A contains three sites consisting o f eleven common genera, Petalconchus, Argopecten, Barbatia, Chama, Chione, Isogonomon, Pinctada, Diadema, Porites, Nassarius, and Area. None of the common genera are found, in all three sites, but the eleven common genera are shared by two o f the three. All. of these genera, except Argopecten, Chione, and Nassarius, with live in sands or tidal flats, are found on or among rocks. Many are commonly found in. both rocky and sandy shore environments (i.e. Barbatia, Isogonomon, and Pinctada). These sites probably represent a rocky shore with sands nearby environment. Subgroup 3.B contains six sites consisting of one com mon genus Porites, and rhodoliths. Of these common fossils, Porites are found at fi ve of the sites, and rhodoliths are found at four o f the sites in this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. < N S 1 «3 as «s ’* §<li 1 Sandy Bottom - J ^ Tidal Flats 'iW % 2 Tidal Flats T7 ; —----- A Rocks and Sands L X O ~ ™ — L f i B Rocks, Corals T7S T90 C Rocks, Lagoonal and Mangrove T§§ 187 ................TSi T4 D Rocks, Lagoonal, j gx and Mangrove TJ 1 6 0 m Rhodolith Beds Rhodolith Beds' 82 Rocky, Sandy, and Rhodolith Bads IT 15 T76 T55 T U > T22 T 6 T58 '1 1 5 T68 ■ n o T 7 1 '1 5 - 1 T86 Til M L 4.< i f r Tidal Flats f'fU 165 O a J r ™ 0.0 0.1 0.2 0.3 0.4 0.5 Euclidean Distances 0.6 Figure 33. Cluster Tree of Q-Mode Analysis of Genera Presence and Absence Counts. Group Numbers, Biofacies and Sample Sites are shown on the left of the figure. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. subgroup, This subgroup represents a shallow water rhodolith and Porites environment. Subgroup 3C contains six sites with the genera Ostrea found at five of the sites and Porites at four. Both of these genera are found in rocky shore environments and in mangrove or lagoonal environments. Subgroup 3D consists of six sites with the genera Ostrea and Chione found at five. Like subgroup 3C. this subgroup probably represents a lagoonal and/or mangrove environment. The last subgroup 3E contains two sites with five common genera, CerUhiunu Cardita, Divalinga, Chione, and rhodoli ths. All of these genera are commonly found in sandy or mud environments and in rhodolith beds. This subgroup, unlike the previous ones, does not represent a rocky environment, but a sandy and/or rhodolith bed environment. In general, group 3 represents a rocky shore biofacies with variations towards combination environments of rocks and sands, and lagoonal/mangrove environments. Group 4 consists of nineteen sites with two subgroups forming at the 0.45 distance. Subgroup 4A contains four sites with three common genera, Chione, Astrangia, and rhodoliths. There are also several other genera that are found in two ou t of three sites, Cerithium, Oliva, Porites, Hipponix, Polinices, and Divalinga. All of these genera, except for Porites and Hipponix, are found in sandy bottom environments. With the presence o f rhodoliths at all the sites, this subgroup most likely represents a rhodolith beds environment. Subgroup 4B contains sixteen sites. The most: common fossils found this subgroup are Porites, Chione and rhodoliths. All th ree of these fossils are found in the common fossil assemblage and represent Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101 both rocky and sandy bottom nearshore environments. All three are also commonly found in rhodolith beds. In general, group 4 represents a sandy bottom biofacies with variations of tidal flat and rhodolith bed environments. Group 5 contains three sites consisting of one common genus, Cardita. Several other genera are commonly found shared between two o f the sites, Olivella, Turbo, Trigoniocardia, Anadara, Barbatia, Chione, Ciena, Plicatula, Tetraclita, PociUopora, and rhodoliths. A majority of these genera are found in sand or tidal flat environments. A few of the genera (i.e. Cardita, Turbo, Tetraclita, and PociUopora) are also found attached to rocks. This group probably represents a sandy bottom or tidal flat biofacies with some rocks or small stones in or nearby. Discussion Cluster analyses of the fossil genera and the sample sites indicate three general habitats: sandy beaches, rocky shores, or tidal flats. These same three habitats are tbund in the modem Gulf, and are described in the literature (e.g. Brusca, 1980; Kerstitch, 1989). There are variations in the habitats. Clusters also form subgroups that distinguish other habitats, for example the rocky shore clusters indicate smaller habitats of lagoonal/mangrove, intertidal rocky, rocks with corals, and rocks with sands environments. As well, sandy beaches and tidal flat environments also separate rhodolith beds from non-rhodolith beds. In a comparison of the two Q-mode analyses, most sample sites are generally grouped in the sam e biofacies. For example, T samples 84,35,43, 15, 38, 63, 11, 41 and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102 44, are all found in sandy beaches and tidal flat biofacies, while the T samples 89, 90, 80, 9, 77, 45. 67, 3, 69, 87, 81, 1, 60, and 39 are found in rocky shore biofacies. Other sample sites, however, are found in different biofacies when compared from one cluster tree to the other. Samples, such as T6, T10, T82, and T83, can be found in both rocky shores and sandy beach biofacies. This could be interpreted that; these localities are very close to each other, and when the organisms die they are swept together. Or, this could indicate that these samples represent more of a storm deposit, where organisms from several habitats have been washed. Regional aspects of the c luster analyses indicate that the areas north of the Rancho Las Animas area, such as El Coyote, Potrero, Road Pit, and Road Cut, have similar biofacies. The El Coyote paleo-lagoon appears in the rocky shore biofacies under the subgroup lagoons and mangroves. Potrero and Road Pit both contain fossils from the tidal flat biofacies, and Road Cut samples contain rhodolith beds, tidal flats, and corals biofacies. In the Las Animas terrace deposits, the biofacies follow' a general pattern of large corals falling into the rocky shore biofacies under the lagoonal/ mangrove subgroup, and the tops of the terrace deposits indicating sandy beaches, tidal flats and/or rhodolith beds biofaci.es. Comparisons of the terrace facies to the clusters in the cluster analyses indicate a general correlation between the two. The Fossiliferous Sands unit is grouped with the sandy beaches and tidal flat biofacies, some are also subgrouped with rhodolith beds. The Large Coral Unit is generally clustered into the rocky shore biofacies and subgrouped with the lagoonal/ mangrove biofacies. The Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103 placement of the Large Coral Unit in the lagoonal/ mangrove biofacies is most likely because the large coral samples almost always have Ostrea sp, with them. The most common Ostrea species, Ostrea pamula, is found in several different habitats, they are found either attached to rocks, mangroves, or reefs. The Pontes, Molluscan and Rhodolith Sandy Marls Unit are found in just about all the biofacies, because the presence o f both corals and rhodoliths imply both rocky and sandy env ironments. The subunits o f the Porites, Molluscan and Rhodolith Sandy Marls fall into slightly different biofacies. The Porites and Molluscan Sandy Marls are found in either the tidal flat or the rocky lagoonal/ mangrove biofacies, while the Rhodolith and Molluscan Marls are found in the tidal flats and rhodolith beds biofacies. This make sense because the corals in the Porites and Molluscan Sandy Marls need some place to attach themselves, so placement in the rocky shore biofacies is valid. While the placement o f the Rhodolith and Molluscan Marls with the rhodolith beds biofacies is another valid grouping. Other terrace facies such as the Beach Gravels Unit and the Conglomerates Unit are grouped with the tidal flat and sand with rocks biofacies, respectively. In general, the cluster analyses biofacies correlate with the terrace biofacies previously determined from fossils and field observation. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 CHAPTER 4 Stratigraphy Detail stratigraphic sections were measured and described at the sites shown in Figures 34 and the results are summarized here. Detail descriptions o f individual sites appear in Appendices D and E. Results Locality Animas North A t the largest and most southern o f the three ten-ace segments. Animas North, two-dozen localities and stratigraphic sections were described. These sites are represented in schematic diagrams in Appendix E. Two sections. Site D2S9 and D3S5, are explained in greater detail. D2S9 A t Site D2S9, located 24°32.515’ W and 110°44.559’ N on the western side of the terrace, the exposed terrace deposits consists of a 2.3 m bed of Porites panamensis. The base of the bed is covered with talus (Figure 35). Corals are in filled w ith sands and shells, which are washed away to help form the surrounding talus (Figure 17). Several layers of horizontal corals and rubble can be seen. Three bulk samples were taken, the first 2 m above the talus top, the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 Northern Cross-sectitar Dune Southern Cross-section Northern Cross-section Middle Cross-Section Km 26 Southern Cross-section Northern Cross-section Animas North Middle Cross-section 1 km •Southern Cross-section Figure 34. Rancho Las Animas Terrace Map with sites. Profile lines drawn through Terrace Segments. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Site D2S9 Height Stratigraphic Facies in m Column T Large Corals Storm Layer Large Corals (Covered) Figure 35. Stratigraphy and Detailed Facies atSite D2S9, Anitnas North Terrace Segment. 107 second at 2.3 m, and the third 2.5 m. Where the first bulk was taken, a one sq. ft area was marked off and the following fossils identified: three Pinctada mazatlantica, one Chama squamuligera, six Isogonomon chemnilzianus, one Chama sordida, and several sea urchin spines. D3S5 Site D3S5 is located at 24° 32.381'W and 110° 44,394'N. Approximately six meters of Pleistocene deposits are seen here (Figure 36). At the bottom 30 cm above the Cerro Colorado Member, is a layer of molluscan and PociUopora sp. fragments and angular cobbles from the underlying Cerro Colorado. The bottommost portion of this layer is filled with Ostrea sp.. A 1 sq. ft area at this horizon reveals eight Chione califoriensis, one Isogonomon chemnitzianus, one Encope sp., one Pinctada mazatlantica, and one PociUopora sp.. Coarse pebbly sands overlay the last layer, filled with more molluscan and Porites sp. fragments. The next layer is a thin irregular rhodolith sands horizon, overlain by approximately 5 meters of massive Porites sp.. At the bottom of the Large Corals Unit, sm all branching PociUopora sp. is found. Horizontal rubble layers interrupt this Large Corals Unit. About 1.5 m above the top of the talus is the thickest of these rubble layers. This rubble layer contains rhodolith fragments, cobbles and m olluscan shells, varies in thickest with the thickest part at 60 cm. Bulk samples were taken tit the base of the outcrop, 0.6 m above the base, and a third sample at 1 m above the base. Coral samples for dating were taken at this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Site D3S5 Height Stratigraphic Facies in m Column 0m > o Large Corals Storm L a^r Large Corals Stomi Layer Large Corals !St52»OijierZ Conglomerates Cerro Colorado Mbn Figure 36. Stratigraphy and Detail Facies at Site D3S5, Animas North Ten-ace Segment. 109 locality; one at about 0.5 m from the base and the other at 2,5 m. No conglomerates, as those seen in D3S2, are seen at this locality. Locality Km 26 Stratigraphic columns for over a dozen localities were measured at locality Km 26 (Appendix E). The two Sites D6S8 and D6S12 are described in greater detail below. D6S8 This locality is a 60 m channel, filled with reworked Cerro Colorado and Porites panamensis, located towards the southeastern tip o f terrace Km 26 on the beach (Figure 37). At its maximum, the channel extends 10.5 m high above the talus. The bottom layer varies between 0.3 - 1.2 m in thickness and consists of either reworked Cerro Colorado or a channel filled storm layer filled with Architect,onia placentalis, Isogonomon chemnitzianus, and urchin spines. This layer is o verlain by the Large Coral Facies o f approximately 8 m of large bouquet shaped P . panamensis. Occasional horizontal and rabble layers interrupt this layer. Molluscans, also found within this layer, are Plicatula inezana, very small Pinctada mazatlantica, Diodora inaequalis, Serpulorhis sp., Isogonomon chemnitzianus, and Barhatia reeveanna. There are two different coral morphologies found at this site: the large and common bouquet shape with some head reach up to 1.5 m i n height, and the platy shape where several layers of coral Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110 M 3 c s s o ; s ■ 4 3 M 00 f ! :§ > a '53 « S3 0 0 ^ ^ ^ I ^ OO un § ~s D O Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 37. Stratigraphy a n d Detailed Facies a t S ite D6S8, K m 2 6 Terrace Segment, are seen forming plates over the older bouquet shapes (Figure 16). The top of this section is capped with lm o f fossiliferous sands. A . bulk sample was taken at the bottom o f this unit and at the top. D6S12 Located at 24° 33.782'W and 110° 44.761’ N on the western side of Terrace Km 26 is Site D6S12. Seven meters of Pleistocene deposits occur above the talus at this local ity (Figure 38). Less than 0.5 m o f reworked Cerro Colorado occurs above the fossiliferous talus; a bulk sample was taken at this layer. Approximately 6.5 m o f Porites panamensis corals overlay the previous layer. Coral heads are up to 71 cm in height. Occasional storm layers of horizontally oriented coral fragments interrupt the coral bed. Pinctada mazatlantica, Chione lumens, Semele bicolor, and Dosinia sp. are common molluscans seen throughout the sandy matrix between the corals, as well as shell fragments and rhodoliths. At approximately 1 meter above the talus, fossils were identified and counted within a 1 sq. ft. block: 3 Isogonomon chemnitzianus, 3 Turbo squamiger, 1 Chione sp., 1 Anadara sp., 3 Astrangia sp., and fragments of shells and rhodoliths. Another bulk sample was taken from the top of the corals' section. Loalily Dime Nearly two-dozen, significance stratigraphic sites are found at Terrace Dune (Appendix E). Sites D8S3 and D12S6 are discussed in greater detail below. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112 b ; * H I ( Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 38. Stratigraphy a n d Detailed Facies a t S ite D6S12, K m 2 6 Terrace Segment. One hundred meters east from site D8S2, on the southern side of Terrace Dune (24° 34,1.78'W and 110° 44.585'N), is site D8S3. Figure 39 shows the site, schematic diagram and facies of Site D8S3. The base o f the terrace is 6 m above sea level and the top about 20 m above sea level The lowest unit above the talus is a reworked Cerro Colorado sands filled with Pocillopora sp,. One meter above the Pocillopora sp. unit is a 2 m unit o f "Pencil" Pontes panamensis and Molluscan sands. Common molluscans found in this unit are Pinctada mazailantica, Anadam sp., Trigonicarium biangulita, Chione sp., Barbatia sp.. Overlaying the "pencil" Pontes unit is 2 m of the Large Corals facies. Capping this unit are beach sands and gravels. Cobbles are up to 5 cm in length, Common fossils found among the cobbles are Chione sp., Anadara multicosta, and Trigonicarium biangulita. D12S6 Site D12S6, located 90 m southeast from site D8S5 at 24° 34.168'W and 110° 44.383’ N, rises 20 m above sea level (Figure 40). The base o f the terrace is at about 6 meters above sea level with three meters of talus rising before the Pleistocene deposit is revealed. Overlaying the talus is three meters of large Pontes panamensis corals. The massive corals unit is overlain by 4 m of "Finger" Porites and Molluscan Sands. Common molluscans found within this layer are Chione sp ., Pectens, Chama sp., Turritella sp., Serpulorbis sp., Ostrea palmula, Plicatula inezana, Spondylus princeps, Strombus sp., and Turbo squamiger. Above Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Site D8S3 Height Siratigraphic in m Column Facies ■ ill Om Beach Gravels Large Corals "Finger" Porites and Moiloscan Sandy Marls 35miD, o q H p O ! (Covered) Figure 39. Stratigraphy and Detailed Facies at Site D8S3, Dune Terrace Segment Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Site D12S6 Height Stratigraphic in m Column 3— Facies r ■■■ Beach Gravels Fossiliferous Sands "Finger' Porites and Molluscan Sandv Marls Large Corals (Covered) Figure 40. Stratigraphy and Detailed Facies at Site D12S6, Dune Segment. 116 the Porites and Molluscan sands unit is 1.5 meters o f Fossiliferous Sands with cobbles. Cobbles are no larger than 3 cm in diameter and range in colors between brown and red. Fossils within this unit are Chione sp,, Oliva sp., Pec tens, Trigoniocardia biangulita, m&Anadara multicosta. Capping this site is 1.5 meters of Beach Gravels facies. This unit is filled with cobbles as large as 4 cm in diameter and shell fragments. Road Cut The Road Cut Site is located a couple kilometers north o f the Dune terrace segment and is the furthest north in locality. Located at 24° 35.644’ N and 110° 44.794'W, Road Cut is a small 5 meter high outcrop along the side of the road showing alternating layers of "pencil" - size Porites sp. and storm layers (Figure 41). The base o f this outcrop is 0.75 m of Cerro Colorado Member, overlain by the Basal Conglomerate Facies filled with gravel, coral fragments, and large clams. Clasts o f Cerro Colorado Member are up to 20 cm in length. On top of the conglomerates is a 0.7 m unit of Rhodolith and Molluscan Sands Facies with burrowing clams and occasional coral fragments. Overlaying this layer is a unit of Large Corals approximately 20 cm in height filled with small Porites panamensis no bigger than 10 cm in height. Above the coral unit is another small layer about 20 cm in size filled with Fossiliferous Sands Facies. Overlaying the sands unit is a 25 cm unit of storm deposits filled with horizontal coral fragments. A unit of "Pencil" Porites and Molluscan Sandy Marls continue above the storm deposit for Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Site Road Cut Height inm V V 4 y 3 V 2 J1 Stratigrapliic Column 0 m V*. v . T " 0 r z s 5 » & ^ a D O ^ Facies Stem Layer "Pencil" Porites and Molluscan Sandy Mai s Stem Layer "Pencil" Porites etc. tllonn Layer ^ Fossiliferous Sands _ ^ ‘ P e n c il2 P o n te s e tc — Rhodoliths and Molluscan Sands Conglomerates Cerro Colorado _ M b n . Figure 41. Stratigraphy and Detailed Facies at Site Road Cut. 118 another 20 cm before a larger Storm Layer o f about 35 cm interrupts it,. The "Pencil" Porites and Molluscan Sandy Marls Facies reappears above the storm deposit and continues up for a meter before this outcrop ends with another Storm Layer deposit. Discussion Locality Animas North Northern Side - A comparison o f the east and west sides o f the northern part o f the Animas North, Terrace reveal a similar facies pattern, large corals topped with Rhodolith and Molluscan Sands. The only difference is the east side is capped with beach sands containing no fossils (Figure 42). Middle - From east to west, there are two different environments present. The east side has a series of storm layers capped with large corals, Rhodolith and Molluscan Sands and topped with Beach Gravel. As seen in the schematic diagram of the middle cross-section of Animas North Terrace (Figure 43), the western side only indicates Large Corals. Southern Side - This area is similar to the middle of the terrace. The western side demonstrates Large Corals’ capped Conglomerates where the talus is washed away. While th e eastern side contains no Large Corals, but Rhodolith and Molluscan Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Legend La 0 Porites, Molhisean 24 and Rhodolithic Sandy Marls "Pencil" Porites and Molluscan Sandy Marls Large Corals Fossiliferous and Reworked Cerro Colorado Sands r L I Basal L a Conglomerates Cerro D5S2 D5S11 I Legend Continued Beach Gravels t j Fossiliferous £53 Saw fe Rhodolith Mottuscan Sandy Maris D5S3 2 1 *' • ■ * 1 I Colorado Mbn, ¥— * H f > W V Cerro Colorado Mbn. Distance in Kilometers Figure 42. Stratigraphic Profile of Northern Animas North Terrace Segment. Legend Listed on the Sides. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. D2S9 D5S14 Storm Layer Storm Layer _ 24 _ 22 I 20 - 18 a: _ !6 s! _ M'S* Dune Cerro Colorado Mbn. 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Distance in Kilometers Figure 43. Schematic Diagram of Terrace Segment Animas North Middle Profile, Legend on Figure 42. N > ® Sands overlain by "Pencil” Porites and Molluscan Sands and capped with Beach Gravels (Figure 44), Comparisons and Contrasts - Comparisons o f the facies throughout: Animas North Terrace indicate five patterns within the facies. Rhodoliths (i.e. Rhodoliths and Molluscan Sands) are only found in the north and eastern sides of the terrace. Beach Gravels are found only on the eastern side. "Pencil” Porites and Molluscan Sands are found in the southeast, while Conglomerates are only found in the southwest. The fifth facies pattern demonstrated at the Animas North Terrace is there are no Fossiliferous Sands. All Molluscan facies present at this terrace are also with other organisms (i.e. corals or rhodoliths). Several depositional environments occur at Animas North. The typical stratigraphic sequence is the Cerro Colorado Mbn overlain by Conglomerates, Large Corals, followed by Rhodolith and Molluscan Sands, "pencil" Porites and Molluscan Sands and capped by Beach Gravel. Since the Conglomerates are only present in the southwestern part of the terrace and appear to be volcanics from the western Miocene escarpment, it is most likely the conglomerates came from, outcrops from the southwest deposited by a retreating alluvial fan. As the shoreline transgressed, large branching P. panamensis corals grew on top of the conglomerates and occasional oyster beds in the shallower-most parts of the terrace and continued to grow new colonies on top o f the old as the sea level rose and reached its peak. Occasional storms would break parts of the colonies and redeposit them as horizontal coral units. As the sea level regressed, the large Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 ^ . 1 i l * i < . < IM 1 Height in. Meters • * > * 3 ' N O W « 4 m o ?5 r*i <s r4«™ — • -* — > so '* 'st r» o t L»J.,.,i...J.»JL.JU«LJ— 1 • jSUL. I H 5 T i J t L ‘P» t \ .......i.......1........1.........i........ T a ~ T 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 44. Schematic D iagram o f Animas North Terrace Segment Southern Profile. Legend o n Figure 42. 123 brandling P. panamensis no longer dominated the paleoembayment, but were overfilled and covered by Rhodolith, Molluscan or Fossiliferous sands. Rhodoliths are found only in the northern and eastern parts of the terrace, indicating possible cross-current flows to the north and east. With the continuing regression o f the sea and the approach o f the shore, rhodoliths sands gave way to beach gravels and cobbles. Km 26 Terrace Northern Side - As illustrated in Figure 45, from east to west on the northern side of this terrace the only facies seen are thick units (>5 m) o f the Large Corals Facies. Middle - Traveling east to west, Figure 46 shows the change from the Large Corals facies to the "Finger" Porites, Rhodoliths and Molluscan Sands in the middle cross- section o f Km 26 Terrace. Southern Side - The southern part o f the terrace contains the most variability (Figure 47). The eastern side demonstrates Large Corals, topped by Fossiliferous Sands. The middle of the terrace contains no Large Corals, but Beach Gravels capping Cerro Colorado Mbn. This transitions from Large Corals, topped with Rhodoliths and Molluscan Sands, to, in the westernmost part of the southern half, into Fossiliferous Sands overlain by Large Corals topped with Rhodoliths and Molluscan Sands. Comparisons and Contrasts - Comparisons of the facies throughout Km 26 Terrace indicate four patterns within the facies. First, "Finger" Porites, Rhodoliths and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.24 Height in Meters *4 « M O 00 S O 'tf * « > • * O CM C H 0 4 *«* ! *"* »"-* <30 s o " * t r 4 L ~J S , J . A,-,,,,L, L m « L,, JL L .„jU 4, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 45, Schematic D iagram o f K m 2 6 Terrace Segment Northern Profile, Legend o n Figure 42, 125 in Meters o J O 00 p ; v o 1 o c m Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 46, Schematic D iagram o f K m 2 6 Terrace Segment Middle Profile, Legend o n Figure 42. 126 Height in Meters ^ O V O < N f o i ^ t s > < n < S 0 2 o o r - - ■ < • v - > o o 3 5 * = r < > o t> o 00 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. [ Distance i n Kilometers____________________________ F igure 47. Stratigraphic Profile o f Southern K m 2 6 Terrace Segment. Legend o n Figure 42. 127 Molluscan Sands are found in the middle west o f the Km 26 Terrace. Second. Large Corals are seen throughout the terrace, except at the highest parts of the Terrace, located in the eastern-most part in the Middle and in the middle of the southern part of the terrace. Third, Rhodoliths are only found on the southwestern side of the terrace, and last, Fossiliferous Sands are mainly found on the eastern side. As with the Animas North Terrace, Km 26 Terrace contains several depositional paleoenvironments. With the onset of the transgression, topographic lows were in-filled with reworked Cerro Colorado Mbn sands and fossiliferous sands. As the sea level rose, the large branching Porites panamensis became established inside these small runoff channels. At the interglacial maximum, P. panamensis covered much of the terrace surface. Later generations of P. panamensis interrupted by storm units, filled the channels reaching up several meters to cover the tops o f the terrace. In areas facing the Gulf, P. panamensis .morphology changed to plate-like shapes, indicating more resistant forms to wave action. Like the Animas North Terrace, the drop of the sea level stopped the dominance o f Porites panamensis, and introduced the closer to shore en vironments of the rhodoliths and molluscans. Rhodoliths are found only in the southern areas of the terrace, indicating a crosscurrent flow to the south o f the terrace. On the highest parts of the terrace, Beach Gravels cap this sequence. Grain size analyses indicate that of al l the terraces, Km 26 terrace had the least amount of wave and/or Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 128 current energy, this may be due to the other two terraces taking the majority of the wave/current force away. Locality Dune Northern Side - From east to west, the stratigraphy changes from Large Corals capped by "Pencil'’ Porites and Molluscan Sands to Large Corals capped by Fossiliferous Sands (Figure 48). Southern Side - From east to west, the stratigraphy changes from Large Corals overlain by "Pencil" Porites and Molluscan Sands, topped by Fossiliferous Sands and capped by Beach Gravels to only Large Corals in the west (Figure 49). Comparisons and Contrasts - Comparisons of the facies throughout Dune Terrace indicate five patterns within the facies. First, "Pencil" Porites and Molluscan Sands are found only in the south and northeast areas o f the terrace. Second, Beach Gravels are seen on the tops o f the highest points to the south and the west of the terrace. Third, rhodoliths are only found in one locality in the middle of the southern end. Fourth, Oyster Beds are found in the inner side of Dune Terrace. And lastly, Large Corals are found about everywhere in the Dune Terrace. The furthest north of the three terraces, the Dune Terrace indicates a similar pattern to the other terraces. On eroded surfaces of the terrace, large branching Porites panamensis are found throughout growing a couple meters up as sea level reached its maxima. As the sea level dropped and currents and or wave action increased from the north, the large P. panamensis disappeared and smaller “pencil” Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. D8S9 D8S10 D13S1 D13S2 _ D9S6 Dune tune Cerro Colorado Mbn. Faait 0.5 0.3 0,1 0.9 0.7 0.6 Distance in Kilometers 0.4 0.2 Figure 48. Schematic Diagram of Dune Terrace Segment Northern Profile. Legend in. Figure 42, 130 Height in Meters © « W " jqJ S \ sp *n ^ O o o o O S C O ” ^g8Pl tia te ■n , o , ? r T ' , Q \ 0 0 i> S D V > m 0 0 C ? \ o os oo r- so c o o os oo so o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 49. Stratigraphie Profile o f Southern D une Terrace Segment. Legend i n Figure 42. sized P. panamensis and mollusks moved in. With the continued drop in the sea level, corals disappear altogether and only fossiliferous sands and beach gravels communities remained. Grain size analyses indicate that some of the greatest amount o f wave and/or current activity occurred at the Dune Terrace, this could indicate that the majority of the current came from the north o f the pa 1 eoembay merit, Comparison o f Terrace Stratigraphy There are several differences and similarities in the stratigraphy between the three terrace segments. All the localities contain the Large Corals facies overlain by one o r a combination of the smaller Porites facies, rhodoliths, molluscan sands or beach gravels. Another similarity is the presence o f rhodoliths on facing sides of Animas North and Km 26. This area between the two terrace segments could be interpretive as an area o f constant fluctuating currents and/or waves to allow the rhodoliths to flourish. Beach Gravels are another similarity, these units are always found on the top of the terraces and are generally found on the easternmost side of the terraces, implying the very end of the regressing shoreline. Differences between the facies appear to be due to either the absence of a particular facies or topography. For example, both Rhodolith and Oyster Mounds are found only on the top of Animas North. This, however, might be a reflection of preservation being better on the larger terrace. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 132 Regional Area Model The Late Pleistocene deposits at Rancho Las Animas are a depositional cycle o f transgression and regression during the last interglacial. Before the sea level rose, the region around Rancho Las Animas was probably much like modem topography with occasional Miocene ridges stretching out to the coast. Because the highest points on Km 26 Terrace Segment are only covered with, a thin layer of beach gravels it was probably the highest point in the shoreline topography. The shoreline terrace was repeatedly cut, forming channels. As sea level rose, basal conglomerates, oyster beds and reworked Cerro Colorado sands were deposited across the landscape, filling in the channels and forming a paleoembayment that stretched from south of Rancho Las Animas to El Coyote. With the transgressing sea and increasing winter temperatures, Porites panamensis flourished, first attaching to the floors o f small channels and then later to the tops o f the terraces and across the sea floor in large coral thickets, growing into large branching colonies as the sea level increased to its maximum. Strong storms occasionally hit the paleoembayment, breaking and redepositing the P. panamensis on top of the old colonies, where new ones would eventually grow. As sea level, decreased so did the size of P. panamensis. Smaller, finger-sized forms of P. panamensis, similar to those growing today, flourished along with rhodolith beds and indigenous molluscans. Small faults formed, cutting through and between the terraces, possibly forming small hydrothermal seeps such as those found in Bahia Concepcion (Fenburg et al, 2002). Rhodoliths and. corals finally retreated as the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 133 sea level became too shallow, and nearshore sediments and beach gravels soon covered the tops of the emerging terraces. Subsequent sea level drops led to deposition of fanglomerates on top the western sides of the terrace segments. Faulting continued, elevating and gently tilting the terrace above the current sea level. Erosion due to storm events cut the terrace into smaller ones segments. Lastly, modern coastal dunes covered the terrace tops. Typical Depositional Terrace Model A general transgress!ve-regressive (Figure 50) sequence begins as basal conglomerate made up o f gravels from the western Miocene scarp. As the sea level rose, fine to medium size sands, reworked from the Cerro Colorado Member, filled with sandy beach to shallow offshore fossils, covered the conglomerate and storm deposits. In channels and lower lying areas within the terraces, large Porites panamensis corals became established, along with populations of offshore molluscan species. Sea level reached, its maximum to support corals, which were now up to 10 m in height above the channel filled sea floor. As the sea level dropped, the large Porites were replaced with smaller thinner Pontes morphologies and shallower molluscans species. Continued sea level drop replaced these environments with tidal and sandy flats populated by abundant rhodoliths, followed by deposition of beach sands and gra vels. The top of this sequence ends with modern coastal dunes. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 134 Facies Beach Gravels Fossiliferous Sands Pontes. Molluscan and Rbodolithic Sandy Marls Large Corals Fossiliferous and Reworked Cerro Colorado Sands Basal Conglomerates Cerro Colorado Member Figure 50. Schematic Diagram, of Typical Transgressive-Regressive Facies Model. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 135 CHAPTERS Grain Size Analyses Introduction Grain size analyses provide a powerful guideline for interpreting the deposition^ conditions of a locality (Pettijohn et aL, 1972; Lewis and MoConchie, 1994). The sizes o f particles reflect several processes; 1) The availability of different kinds and sizes o f particles from different kinds of source bedrock or even preexisting sediments, 2) the resistance o f particles to weathering, erosion, and abrasion, and 3) the processes of transportation and deposition (Friedman and Sanders, 1978). One method o f analyzing the grain size of particles is look at the distribution o f the grain sizes. The distribution of the grain sizes in sediments is related to: 1) the availability of different sizes of particles in parent material and 2) the processes operating where the sediments are deposited. Two methods are used to determine quantitative analyses of grain sizes, the normal distribution or size- frequency curve and the cumulative-frequency curve. Plotting the proportion percentage versus various particle sizes makes a size-frequency curve. The cumulati ve-frequency curve differs from the simple frequency curve in that each point represents not merely the frequency o f each size, but rather the sum of all the percentages o f the preceding sizes. Quantitative analysis serves to characterize grain size distributions precisely, and permits statistical distinction of similarities and differences between samples. There are four different features that can be Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 136 determined by a quantitative grain size analysis: mean grain size, sorting, skewness of grains, and kurtosis. In using statistical methods, the normal distribution is defined in moments. The first moment o f the distribution, is the mean. The main grain size in a deposit is largely a function of the process energy controlling transport and deposition: particles are segregated according to their hydrodynamic behavior, which largely depends on their size (although specific gravity and shape are also very influential). The mean o f grain size can show one o f two processes: central tendency and bimodality. Central tendency occurs when the grain size o f sands is clustered around an average value (e.g. mean), this is controlled by a combination of two factors: 1) the average competence of the depositing medium, and 2) the initial size of the source material. Bimodality results from a variety o f causes: 1) a combinat ion of bed and suspension load transport, 2) infiltration, 3 ) post- depositional diagenesis, 4) a lack of certain size grades in some source materials, or 5 ) two sources contributing to sediment deposition. The second moment of the distribution is a measure of dispersion about the mean. It represents the numerical value of the standard deviation squared. In populations of particles, the standard deviation provides information on the extent to which particle sizes are clustered about the mean and defines sorting. The degree o f sorting o f grains in the deposit is a function of the persistence and stabili ty o f those energy conditions (i.e. fluctuations in velocity, contributions from suspension as well as traction transport to the same bed, sampling more than one Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 137 sedimentation unit, and source sands with more than one mode contributing to sorting variation). The size distribution in sediments may also be strongly influenced by source rocks (e.g. a source o f sediments may already be sorted). The third moment of the distribution is a measure of the symmetry of the frequency curve about the mean. This moment is the mean cubed deviation and by testing the symmetry o f the curve, determines its normality. The third moment yields deviation from symmetry or skewness. This indicates that particles in excess of the normal distribution are present in coarser or finer fractions. This information can be used to interpret how particles were deposited. Finer or positively skewed graphs usually indicate high-energy environments where the finer particles are winnowed out leaving behind larger particles. Nearly symmetrical graphs represent more vigorous 2-way flow environments where the both large and small particles are winnowed out or a moderate energy deposition environment. Coarser or negatively skewed graphs indicate a low energy environment in which the fine grained suspension load has been deposited. The fourth moment is used to calculate the peakness, or kurtos is o f the distribution. Results Selected bulk samples from the three terraces were analyzed for grain size distributions, and examined under a microscope for grain type distributions (see Appendix F for values). Since the normal size frequency graphs were greatly Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 138 skewed towards the -4.5< j> due to fossils in the samples, the small grain size fractions (i.e. the matrix) will be used in the discussion. Moment calculation results for these samples can be see in Table 1. Distribution o f the samples’ grain sizes versus frequencies can be seen in Appendix G. Discussion Locality Animas North Comparison of Site D1S13 Samples Samples T59, T58, and T81 all come from the same location, but different elevations (bottommost to topmost, respectively). Each of the three samples were from different facies, sample T59 is from the Fossiliferous and Reworked Cerro Colorado Sand Unit, T58 is from the Fossiliferious Sands Unit, and T81 is from the subfacies Rhodoliths and Molluscan Sandy Marls. Regardless of facies, the sorting and num ber of grain populations/sources generally stay the same over time. Skewness, however, changes from nearly symmetrical to fine skewed to coarse skewed, implying that the mode of deposition of the grains have changed from a more vigorous 2-way flow to a one-way higher current flow and finally to gentler flow. T h is is possibly due to a change in depth of the overlying water. Comparison of Site D2S6 Samples Samples T53, T54, and T55 are from site D2S6 and collected from the bottommost to topmost beds. All three samples were taken from Fossi liferous Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 139 Table 1 G rain Sfcse Analyses T no. Std Dev m ' 8 s 1 i . 1 l . „ l l l l .. _ Small Fraction Std. Dev. Small Fraction Skewness Sample Grain Phi % White Material %Color Material T58 2.74 1.24 0.42 2.45 0.24 -1 90 10 3.625 90 T66 2.68 -0.89 1.04 2.68 -0.89 2,5 90 1 0 T53 2.64 4)38 1.37 1.78 -0,18 -1 90 10 2.5 90 1 0 T54 3,06 0.08 0.98 2,33 -0.4 -1 90 10 1.5 90 10 T55 2.47 -0.34 1.47 lift -0.45 -1 90 10 2.5 85 15 T60 1.31 4.62 0.68 2.56 -0.32 1.5 95 2.5 90 T67 1.15 3.77 1.49 1.41 -0.07 0.5 98 1.5 98 2.5 98 rss 1 M 2.9$ o.iij 2.56 0.03 ~ A l o o 2.5 90 T62 1.29 2.58 2.67 1.78 -0.97 -1 2.5 95 5 3.625 95 5 T63 3.11 0.64 2 1.75 -0.72 -1 2.5 _____95 5 3.625 T68 2.22 -0.39 0.84 2.22 -0.39 2.5 S O 50 172 0.05 0.92 2.16 -0.08 -1 50 50 2.5 70 30 T87 1.98 2.61 0.39 2.29 0.27 -I 100 T89 2.43 1.62 -0.22 2.44 0.1 -1 1 .5 100 T43 3.05 0.43 0.18 2.6 0.09 -1 3.625 ___________100 ~ 0 T47 2.83 1.01 0.54 2.46 0.19 -1 100 3.625 95 T45 2.16 1.74 0.86 1.91 0.51 -1 95 T48 2.69 0.02 0.05 2.69 0.2 -1 100 3.625 95 186 1.84 2.97 -0.45 2.69 0.17 2.5 30 70 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 140 fa b le 1 Continued Too. Std Dev Skewness Snail Fraction Mean Phi Small Fraction Std. Dev. Small Fraction Skewness Sample (3 rain Phi % White Material %Color Material T80 2,98 _ 5 0.32 -0.5 2.5 95 5 T90 1.62 -1.29 1.7 1.62 -1.29 1.5 " 225 50 50 50 ” 50 170 2.08 -0.62 1.63 2.08' -0.62 -t 2.5 95 T70 3.625 95 T65 2.75 0.02 0.23 2.1! -0.27 -1 _____ 1,5 2.5 SO 50 50 1 7 1 1.58! 3.49 0.34 -0.31 1.5r 7o 30 TCI 2.89 0.3 0.75 2.09 -0.21 __________-I 1.5 90 85 10 15 2.5 80 20 F76 1.07 5.78 0.02 2.45 -0.07 -1 98 2.5 98 175 2.54 1.68 -6M 2.66 0.09 -1 75 25 2.5 70 30 T77 1.85 0.38 0.93 1.85 0.38 -1 95 5 2.5 90 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 141 Sands Unit subfacies called Encape Sands, Sorting, skewness, and the number of grain populations/sources generally stay the same over time, The exception is that sample T53 has one more grain source than the other two. Comparison of Site P2S9 Samples Samples T60, T67, and T56 are from site D2S9 and collected from the bottom to the topmost beds. Both samples T60 and T56 were taken from Large Coral Units, while sample T67 was taken from a storm layer within the Large Coral Unit, There are three main differences between these three samples: 1) the change in skewness, 2) the change in grain populations/sources, and 3) change in volcanics percentage. The skewness changes from coarse to symmetrical to fine skewness, indicating the change in deposition flow and energy from high energy to a two-way flow and finally to a lower energy flow. The grain sources change from two to one and back to two populations. Last, the percentage in volcanics present in the sediments change from approximately 10% to less than 5% and back to 10%. These differences between T60 and T56 to T67 can be attributed to sample T67 being a storm layer. Comparison of Site D3S5 Samples Samples T85 and T84 both come from site D3S5 and were collected from the bottom to the top beds. Samples were taken from different facies, TBS is from a Fossiliferous and Reworked Cerro Colorado Sands Unit and T84 is from a Large Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (42 Corals Unit. There are three main differences between these two samples: 1) the change in skewness, 2) the change in grain populations/sources, and 3) change in volcanics percentage. The skewness changes from symmetrical to coarse skewness, indicating the change in deposition flow and energy from a high-energy two-way flow' to a lower energy flow. The grain sources change from three to two populations, indicating that over time one of the grain sources is eliminated. Last, the percentages in volcanics present in the sediments change from approximately 10% to none. Comparison o f Site D5S14 Samples Samples T62 and T63 both come from site D5S14 and were collected from the bottom to the topmost beds. Sample T62 was taken from a Fossiliferous and Reworked Sand Unit and sample T63 was taken from the subfacies Rhodoliths and Molluscan Sandy Marls Unit. Sorting, skewness, and the number o f grain populations/sources generally stay the same over time. Locality Km 26 Comparison of Site D6S8 Samples Samples T7Q and T65 both come from site D6S8 and were collected from the bottom to the topmost beds. Sample T7Q was taken from a Fossiliferous and Reworked Cerro Colorado Sands Unit and sample T65 was taken from a Fossili ferous Sands Unit. Sorting, skewness, and the number of grain Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 143 populations/sources generally stay the same over time. The only difference is the change in volcanics percentage. Sample T70 contains less than 5% whereas T65 has approximately 50%. This increase in volcanics implies an increase in the deposition of materials from the Miocene escarpment to the west to this site. Locality Dune Comparison of Site D8S3 Samples Samples T87 and T89 both come from site D8S3 and were collected from the bottom to the topmost beds. Sample T87 was taken from a Large Corals Unit and sample T89 was taken from a Small PociUopora Unit. The two main differences between these two samples are skewness and the number of grain populations/sources. The skewness changes from fine skewed to nearly symmetrical, indicating a change from a one-way flow to a two-way flow. The change i n the number of grain populations/source from one to two implies that a second source of sediments was introduced to this site over time. Other Localities Road C ut Samples T43, T45, T47, and T48 are from the Road Cut site and collected from the bottom to the topmost beds. All of these samples come from different facies, sample T43 was taken from a Basal Conglomerate Unit, samples T45 and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 144 T47 were from a "Pencil" Porites and Molluscan Sandy Marls subfacies, and T48 was taken from the subfacies Rhodoliths and Molluscan Marls. There are two main differences between the four samples: 1) Skewness, and 2) number o f grain populations/sources. The skewness changes from symmetrical to fine and back to symmetrical, indicating that the deposition environment changed from a two-way flow to a one-way flow and back to a two-way flow. The number o f grain populations/sources changes from three to one to two and back to three, implying a change over time from many sources to one and then slowly back to three grain-populations/sources. Across the Street from Road Pit Sample T86 - The small grain size fraction's standard deviation o f 2.69 and skewness of 0.17 indicate very poor sorting and a fine skewness. The two peaks in the size frequency graph imply that there were two populations/sources for the sediments. The subangular to subrounded shapes of the grains indicate that there was som e transport/abrasion occurring to the grains before deposition. Grain Size Comparisons o f Facies Fossiliferious and Reworked Ceiro Colorado Sand Unit The small fraction mean < j > is > 0 and < 2.7. The standard deviation range is > 1.7 a n d < 2.9, indicating poor to very poor sorting. The skewness is between - I and 0.1 or a strong coarse to near symmetrical skewness, implying a very low to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.45 moderate energy deposition environment. The volcanics percentage range between 0 and 5%, indicating little to none of the sediments originate from the near by Miocene escarpment. The number o f sediment populations / sources were 2 - 3 with 4/5 o f the samples having 2 populations. Fossiliferous Sands The small fraction mean < j > is > 0.2 and < 0.5. The standard deviation range is > 2.1 and < 2.5. indicating very poor sorting. The skewness is between -0.3 and 0.3 or a strong coarse to strong fine skewness, implying a very low to very high- energy deposition environment. The volcanics percentage range between 50 and 10%, indicating approximately one half to a tenth of the sediments originate from the nearby M iocene escarpment. The number of sediment populations / sources were 1 - 2 with 4/5 o f the samples having 2 populations. Subfacies Encope Sands The small fraction mean < J > is > 0.9 and <1.5. The standard deviation range is > 1.7 and < 2.4, indicating poor to very poor sorting. The skewness is between - 0.5 and -0.2 or a strong coarse to coarse skewness, implying a very low-to-low energy deposition environment. The volcanics percentage range is approximately 10%, in dicati n g that a small percentage of the sediments originate from the nearby Miocene escarpment. The number of sediment populations / sources were 2 - 3 with 2/3 of the samples having 2 populations. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 146 Large Coral Unit The small fraction mean < } > is > -0.5 and < 0.7. The standard deviation range is > 2.3 and < 2.7, indicating very poor sorting. The skewness is between -0.4 and 0.3 or a strong coarse to strong fine skewness, implying a very low to very high- energy deposition environment. The volcanics percentage range between 0 and 10%, indicating little of the sediments originate from the nearby Miocene escarpment. The number of sediment populations / sources were 1 - 2 with 3/4 of the samples having 2 populations. Porites, Molluscan and Rhodolith Sandy Marls Unit The small fraction mean < j ) is > -0.1 and < 1. The standard deviation range is > 2.1 and < 2.5, indicating very poor sorting. The skewness is between -0.1 and 0.6 or a nearly symmetrical to strong fine skewness, implying a moderate to very high-energy deposition environment. The volcanics percentage range between 50 and 30% , indicating approximately one half to a one third of the sediments originate from the nearby Miocene escarpment. The number of sediment populations / sources were 1 - 2 with 1/2 of the samples having 2 populations. Subfacies "Pencil" Porites and Molluscan Sandy Marls T h e small fraction mean ( |) is > -0.2 and < 0.8. The standard deviation range is > 1.9 and < 2.5, indicating poor to very poor sorting. The skewness is between - Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 147 0,4 and 0,5 or a strong coarse to strong fine skewness, implying a very low to very high-energy deposition environment. The volcanics percentage range between 50 and <5%, indicating approximately one half to very l ittle o f the sediments originate from the nearby Miocene escarpment. The number o f sediment populations / sources were 1 - 2 with 2/3 of the samples having 2 populations. Subfacies Rhodolith and Molluscan Marls The small fraction mean ( |> is > 0.5 and < 2. The standard deviation range is > 1.7 and < 2.7, indicating poor to very poor sorting. The skewness is between -0.9 and -0.2 or a strong coarse to coarse skewness, implying a very low-to-low energy deposition environment. The volcanics percentage range between <5% and 10. The num ber of sediment populations / sources were 1, 2,3 with 1/3 of the samples having 2 populations. Comparison of the Facies The comparisons and differences o f the above facies indicate a few differences. All coral facies (i.e. Large Corals, "Finger" Pontes, Molluscan and Rhodolithic Sands, and "Pencil" Porites and Molluscan Sands) have the smallest mean p h i, and the Fossiliferous Sands facies have the highest energy./ strongest current depositional environments. This makes sense since only the largest grain sizes will fell out of suspension and be deposited in high-energy areas. The other difference between the facies is the Rhodolith and Molluscan Sands, Encope Sands, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 148 and Reworked Cerro Colorado Facies have the lowest: energy/ weakest current depositional environments. These differences can be seen in a graph of grain size cumulative weight percentage versus grain size, demonstrating typical weight percentages for Large Corals, Rhodoliths and Molluscan Sands and Fossiliferous Sands facies (Figure 51). The cumulative weight percentage graph clearly indicates the different grain size populations between the three facies. The most common similarities were very poor soiling o f sand grains and the present of 2 different sediment populations / sources at the sites. Differences in the populations can be related to either 1) longshore drift versus other local inputs (e.g. volcanic grains), 2) varying strengths of waves over time (e.g. sea level change), or 3) lagoonal sediments versus open shore. Grain Size Comparison o f the Terrace Localities Locality Animas North The small fraction mean < j > is > -1 and < 3. The standard deviation range is > 1.4 and < 3, indicating poor to very poor sorting. The skewness is between -1 and 0.2 or a strong coarse to fine skewness, implying a very low to high-energy deposi ti on env ironmen t. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Comparison of Cumulative Wt. T84 Large Corals Facies T64 Rhodoliths aad Mott. Sands Facies T58 FossUlferoas Sands Facies J W T O * T Mean Grain Phi Figure 51. Comparison Graph, of Grain Size Cumulative Weight Percentages at Three Different Localities. 150 Locality Km 26 The small fraction mean < j > is > 0 and < 1.7. The standard deviation range is > 1.4 and < 3, indicating poor to very poor sorting. The skewness is between -1.2 and -0.2 or a strong coarse to coarse skewness implying, a very low-to-low energy depos ili on cm ironment. Locality Dune The small fraction mean < j > is > -0.2 and < 0.2. The standard deviation range is > 2.2 and < 2.6, indicating very poor sorting. The skewness is between 0 and 0.6 or nearly symmetrical to strong fine skewness, implying a moderate to very high- energy deposition environment. Locality Road Cut T he small fraction mean ( J > is > 0 and < 1. The standard deviation range is > 1.8 and < 2.8, indicating poor to very poor sorting. The skewness is between 0 and 0.6 or nearly symmetrical to strong fine skewness, implying a moderate to very high-energy deposition environment. Comparison of Terrace Localities There are several differences seen between the terraces. Animas North has the largest range of mean phi, as well as the biggest; range in the depositional environment energies (from very low to high). Terrace Dune and locality Road Cut Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 5! have the highest skewness and thus the highest energy depositional environments. Km 26, unlike Dune and Road Cut, has the lowest energy depositional environments. There are two similarities between, all the terrace localities: 1) Sorting (i.e. standard deviation) and 2) number of sediment populations. All the terraces have either very poor or poor sorting, and there does not seem to be a relationship between terrace and number of sediment populations. Another interesting observation is that, the percentage of volcanics increases to the top of the terraces and is present in all samples from the other loca l ities (i.e. Road Cut and Across the Street from Road Pit). This implies that the further up the top of the terraces sediment input from the western Miocene escarpment increases, or that th e shoreline is moving towards the terraces and the heavier sediments are depositing on the terraces. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 152 CHAPTER 6 Uranium-Series Dating Introduction The principle behind 2j0 Th /m U dating is based on observations that the decay o f 238U passes through a series o f relatively short-lived intermediate daughters to 206Pb. The gro wth of Th2 '5 0 toward a state o f equilibrium with its parent U can be used as a measure o f age using the following three assumptions. First, no significant amount o f 2 3 0 Th is initially present in the carbonate. Second, the carbonate has remained in a closed system since its formation. Last, the U /m U ratio in the ocean has remained constant throughout the dating period (Veeh, t T.t 9 1 H 1 966). Due to a 15% excess in the ocean of"' U over its parent "*'' U, the re- attainment o f radioactive equilibri um between these two isotopes after their removal from the ocean can be used as an approximate age determination if the above assumptions are valid. The new thermal ionization mass spectrometer (TIMS) method has improved the precision of uranium age dating (Stirling et ah, 1995; Stirling et ah, 1998; McCulloch and Esat, 2000). The TIMS method, along with precise determination of the initial 234U/2 3 S ti ratio of the coral, allows for a clearer evaluation of the mobilization o f uranium and thorium during diagenesis. However, even with these newer more precise methods, there still are conflicting estimates in the timing and duration of the Last Interglacial period. These conflicts Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 153 may reflect difficulties in determining the reliability of B0Th age (Stirling et al., 1995). Corals have proven to be favorable materia! for uranium series analysis (Veeh, 1966; Ku and Kern, 1974; Edwards et al., 1987) and samples from well- preserved coral reefs were dated. To ascertain whether or not the corals have remained in a closed system, their caieite/aragonite ratios were determined using x- ray diffraction. Previous studies of uranium-series age determination o f terrace deposited in the gulf during stage 5 have indicated ages between 117 Ka to 144 Ka using coral heads (Oniura et a l , 1979; Emerson et al., 1981; Ashby et al., 1987; Sirkin et al., 1990). All previous studies indicated that as long as the corals were nearly pure aragonite (up to 98%), the ages are dependable. However other problems can occur (e.g., excess uranium). Many of these studies compare the coral ages from the Gulf to the coral ages in the Caribbean (Ashby et al., 1987). Results The reliability of ll-series ages is, in . general, based on four criteria: 1) there is little to no evidence of recrystallization, 2) U concentrations are similar to those found in living corals of the same genus, 3) low concentrations of 2 3 2 Th and high 2 3 0 Th/2 ’ ,2Th values, and 4) a calculated initial 82 3 4 U values similar to those of modem seawater (Chen et al., 1991; Gallup et al., 1994; Muhs et al., 2002). While there w as no obvious indication o f recrystalization based from SEM examination of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 154 coral samples (R. Douglas, per, comm,), all the coral samples analyzed have 1) initial 82,,4U values in excess o f those for modem seawater, and 2) higher U concentrations compared to Pontes reported in the literature. Uranium concentrations in Rancho Las Animas corals (as seen in Table 2) average 4.074 ppm and two samples exceed 6.0 ppm compared to values o f 2-3 ppm for most open ocean Porites (Gallup et al., 1994). Initial 52 3 4 U activity values are higher than acceptable (Gallup et al,, 1994, Mulis et al., 2002) and indicate open-system behavior and uncertainty associated with the ages. Samples from the top of the Large Corals facies yielded a tight cluster of apparent ages, ranging from 137.5 to 138.8 Ka. These corals have initial * * V P'1U ratio val ues of 1.1802 - 1.21.11 in excess of the value for modern seawater of 14S±4%«. This is evidence that U has been added, suggesting a bias toward older ages (Gallup et al., 1994; Muhs et al., 2002). While it is not possible to determine precise ages, by using the approach of Gallup et al. (1994) by assuming the initial S2 " '4 U is similar to modem values and that the addition of excess uranium is constant over time, the true ages of the corals at the top of the Large Corals facies may be closer to 128-130 ka. Ages for the samples from the base of the Large Corals facies are older but have even higher 8234U values. Scanning Electron Microscopy of coral fragments did show a thin ( 1-3 micron thick) coating of silica in some skeletal material (R. Douglas, per comm.). The veneer is irregularly distributed within an individual coral head and is most common in the large bouquet-shaped P. panamemis found in the channels. It has Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 155 Table 2 Isoteplc Values and TP-Serles Ages for Corals Sample u ppsn Th ppt» T ti Pg/g today tJ/Th age (kyr U/Th age (hy)** § O initial “ u r u seaw ater age Km26ml0 4354 ± 0.004 191.4 ± 2.4 60.4 ± 0.2 1433 k 0,9 137.5 & 3.7 1403. ± 1.3 211.1 i: 2.6 17 Km26-1 2.658 ± 0.002 137.4 ± 1.4 36.4 ± 0.1 121.7 k 0.8 138.8 k 4.5 141.9-4 1.6 180.2 £ 2.6 74 LAS-N04 4.17 ± 0.005 177.8 ± 1.7 80.3 ± 0.4 172.5 k 1.0 208.6 ± 4.3 210,6 ± 3.4 311.0 £ 4,3 LAS-N07 3.416 ± 0.003 136.1 * 0.06 46.7 ± 0.1 136.4 i 1.2 1383 £ 0.8 138.6* 0.8 201.7 £ 1.8 34 LAS-N bed 2 4.681 ± 0.005 140.9 ± 1.5 69.9 ± 0.2 122.0 i 1.0 170.3 : f c 2.9 172.1 ± 1.7 195.0 k 2,3 73 LAS-N bed 6 6.027 ± 0.008 100.2 d b 0.09 71.8 ± 0.2 127.3 1 1.0 108.7 £ 1.5 ,109.7 :t 0.7 173.1 £ 1.6 68 Km26~ beach 2.663 ± 0.002 177.8 ± 2.0 81.2 ± 0.3 142.2 ± 1.0 excess 2 3 0 T T i. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 156 not been found in the small, pencil-size Porites from beds resting directly on the terrace surface. Discussion The U-series TIMS ages from the Las Animas terrace deposits are similar in precision and broadly overlap U-series ages reported for other late Pleistocene terrace deposits on the eastern Baja California peninsula (Ashley et at., 1987; Szabo et al., 1991; Sirkin et al., 1990; Halfar, 1999; Muhs et a l, 1994, 2002). Ages from these deposits range between 120 ka and 145 ka (Figure 52). In all cases the corals have initial 82 3 4 U values higher than modern seawater. Muhs et a l (2002) found that reanalysis of Porites and Pocillopora specimens from Cabo Pulma (M uhs et al. 1994) using U-series TIMS analysis did not solve the problem and that the corals still yielded older than substage 5e ages (more than 4000-5000 years). Even with the lack of precision, the U-series ages suggest that they all represent the same eustatic sea level event and most likely correlated with the last interglacial high stand period, MIS 5e. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 157 T — T w « .1 % * 2 ># * * * < * * * s > m ft, 3 - f - ) [• - 41 00 ^ B © A ] & a S 2 " f tagjt * n * « c i — -i— "i— r o U Ti O O o *r« o *r © <n J n »*' © (|K « J a d ) j r „ g Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 234 Figure 52. 5 U(per m il) vs. A ge (ka). Values o f L a s Animas Porites a r e show n i n comparison to M od em Corals, 158 CHAPTER 7 Tectonic Implications o f t h e Terrace Segments Introduction Along the rifted and uplifted coastline of eastern Baja California, marine terraces correlate to sea level high stands and permits an evaluation ofpost- depositional tectonic motion. Measuring the terrace shoreline angles usually determines ancient sea level position. However, the nature of the terraces in Rancho Las Animas usually does not permit this calculation. Instead, the elevation of the wave-cut platform and/or the top o f the Large Corals facies was used as an indicator of Pleistocene sea level. These levels are originally within 1 - 2 m of sea level. Several models (Bradley and Griggs 1976; Edwards et a l, 1987; Muhs et al., 2002a; 2002b) have been proposed for the timing of the Last Interglacial maximum. For a high energy, erosional coastline like Baja California, the model suggests that the early stages of a sea level high stand may be dominated by terrace cutting. Fossils deposited on the terrace surface represent late stages, just before sea level regression. Reef types also complicate the formation of terraces. "Keep- up" reefs are rapidly growing fringe and barrier reefs dominated by Acropora communities that can accommodate rising sea level. "Catch-up" reefs (such as patch reefs) are slower growing types whose development may be delayed until sea level has stabilized in the late stages of sea level rise (Neumann and MacIntyre, 1985; M uhs et al., 2002b). The Large Coral facies o f Rancho Las Animas were Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 159 uncemented open-framework structures that do not easily fit into classic reef terminology but are closest to "patch reefs". The coral colonies are built upon cobbles and reworked Cerro Colorado Mbn that formed the basal conglomerate facies. Oysters and moliuscan fragments indicate that these are marine deposits and represent the early stages o f sea level rise and terrace cutting, as predicted by the model. The Large Coral facies and platform deposits indicate development late in the last interglacial sea level high stand, near its maximum height. Results arid Discussion Calculation of sea level during the last interglacial high stand can be complicated and is often contro versial (see Table 3 ). With the use of high precision U-series TIMS dates and coral reefs data from tectonically stable areas, the early estimates of +9 to +10 m above present sea level for the last interglacial (Shackleton, 1987; Bard et at., 1990) have decreased to less than +5 m. Based on coral reefs from the western Australian margin, MeCuUoch and Esat (2000) calculated the maximum sea level high stand during MIS 5c at about +4 m. Most previous studies of terrace based uplift rates in Baja California have used +6 m as the elevation of the last interglacial high stand (Ortlieb, 1.991; Johnson and Ledesma-Vazquez, 1999; Ashley et at., 1987; Ledesma-Vazquez and Johnson, 2001). For this study the +4 m for the sea level during the MIS 5e and no correction for isostatic rebound was applied. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 3 Uplift R ates o f B aja C alifornia Terraces Location M nlege} San Nicolas El l a jo /S a n F d® o Bahf* Coyote/ Rancho Las Animas El Coyote Punta Colorado Cabo PullttO San Juan Del Cabo Terrace Elevation + 12 - 13 coral rabble + 8 - 9 'reefs' + 13 - 25 ’ reefs* + 7 - 1 0 coral rubble + 5 sand + 6 coral rabble + 6 - 8 sand Age (ka) J24±6 144±7 (125) 1.38+1 137+4 139+4 123±6 135+6 140+6 146+9 (125) 120+1 127+1 139+1 140+4 (125) Rate o f Uplift cm/ka (LI=+4m) 6 - 7 (~4) 9 -1 9 3 - 5 (<D <1 (<D Uplift rates and ages for other localities are found in Ortlieb, 1991; Johnson and Ledesma-Vazquez, 1999; Ashley et ah, 1987; Ledesma-Vazquez and Johnson, 2001. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 161 Three features from the terraces have been used as indicators of late Pleistocene sea level: the beveled surface of the main terrace, the top of the Large Corals facies, and the highest position o f the rocky shoreline. These features are ideal for two reasons: 1) they were all formed within a few meters of sea level, and 2) their present elevation provides a basis for estimating the amount o f post- depositional tectonic uplift in the area. The top of the Large Corals facies is almost always at the same level as the wave-cut platform. This facies was beveled during the regressing sea level and was covered by the small Porites, molluscan and/or rhodolithic sands and beach deposits that cover both the terrace and the corals. lir e elevation values for the Las Animas region were calculated using two different altimeters and measurements of stratigraphy. These altimeters were regularly recalibrated to zero at the beach, however readings with both altimeters did wander over time to increasing values of between 2 - 4 meters. Many elevations were based from the change in altitude opposed to the exact reading on the altimeters. Because of the wanderings of the altimeters and possible human error in the field, some uncertainty exists in the determination of the terrace segments height. The uncertainty is estimated as ±4 meters. In the vicinity of Punta Coyote fan-delta, the topographically highest rocky shoreline deposits at the innermost edge of the ancient embayment are at +18 to +22 m above present sea level. Over much of the central part of the study area the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 162 elevation o f the terrace surface and/or Large Corals facies is +13 to +16 m. The elevation o f the terrace block at Las Animas North is +20 to +25 m. Near the Student Locality, the top of the Large Corals facies is about + 16 m. Outside the study area, the terraces to the south have been measured at 26 m (Nava-Sanchez, per comm., 2002), In the center of the ancient embayment the surface of the terrace platform tilts gently towards the coast, In the shallow bays surrounding the Gulf of California, coral communities live at water depths of 1 to 10 m, with large patch corals limited to <5 m (Squires, 1959; Brusca, 1980; Glynn et ah, 1983). With this in mind, the tops of the Large Corals facies at the time of the last interglacial sea level high stand are assumed at a paleodepth of -3 m. This is a conservative value considering the relief of the channels in which they grew, and that they were eroded during the low stand sea level. Based on elevations of the terrace surface and the top of the Large Corals facies, assuming the corals grew at -3 m, and that the last interglacial high stand sea level w as +4 m, the terraces have been uplifted a minimum of 12-20 m. Assuming the age for the top of the Large Corals facies is 128 lea, the Rancho Las Animas terraces have been uplifted at an average rate of 8 to 15 cm/ka (0.08 * 0.15 m/ka) since th e last Pleistocene (Figure 53). Uplift in the Rancho Las Animas locality is similar to other MIS 5e terraces in the B aja California region between Santa Rosalia and the La Paz peninsula. On the east side oflsla Carmen, a 125 ka terrace is at +25 m above sea level and El Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 163 m > m LU 20 JE 15 C O 10 S ea Level*-. (13-21 m) WL Now Last Interglacial Sea Level + 4 m (McCulloch and East.v 2000) A im uM M M xr st 16 to 21 m Uplift Rate * 1 2 - 1 3 cm/ka Depth of I Living Corals' 1-5 m -128-131 ka BP Figure 53. Schematic diagram of amount of uplift. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Bajo in the Loreto area is at +16 m (Mayer et a t 2002). The marine terraces in the Bahia Coneepeion-San Nicola,s area are about +12 to +13 m (Ashley et a t 1987; Ortlieb, 1991; Leclesma-Vazquez and Johnson, 2001), at San Telmo they are +9 m (Squires, 1959), and the Tecalode-El Coyote terraces are +7 to +10 m (Szabo et a!„ 1990; Sirkin et at., 1990; Nava-Sanchez, 2000 unpublished). These values are in the range of the regional elevation of ea 10 m for MIS 5e terraces along the west coast o f Baja California (Ortlieb, 1991), South of the La Paz Fault, the terrace data suggest that the Baja California peninsula, except lor some local tectonics, has experienced little uplift in the past 125 ka. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 165 CH APTER 8 Rancho Las Animas Paleoenvironments Pleistocene vs. M odern G ulf of California Communities Comparison o f Rancho Las Animas Pleistocene Deposits to Other Pleistocene Deposits Rancho Las Animas deposits are similar to other late Pleistocene deposits found throughout the southern and central coastal areas of eastern Baja California. In Cabo Pulmo, the stratigraphy consists of conglomerates overlain by isolated corals, fossiliferous sands, and capped with sands. San Telmo deposits are oyster beds overlain by 2-3 meters of Porites panamensis, and capped by gravel. Marquer Bay has outcrops o f marly sands covered by corals. At Coronados Island, there are 6 meters of P. panamensis, however these beds consist o f 2 or 3 separate deposits (5a and 5e) (Mayers et a l, 2002). Punta Bajo's deposits are 2 meters of large P. panamensis. The furthest north Pleistocene deposits with corals are those found in Punta Chivato. At Punta Chivato, Pleistocene deposits overlay Miocene volcanic breeca and Pliocene basal conglomerates with in situ and jumbled P. panamensis coral heads of 10 cm high on average. Terrestrial sediments and rhodoliths divide the generations of corals (Ransom 2000). Although there are many similarities between the Pleistocene deposits found in the Gulf of California, there are a few large differences in comparison with the Las Animas deposits. These differences lie in the completeness of the transgression- regression cycle seen in the stratigraphy, the extent of the P. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 166 panamensis growth, and the formation o f Pleistocene deposits on top of raised topography. Comparison o f Pleistocene deposits to Modern GulfFauml Communities Pleistocene faunal communities are still living in the modern Gulf. The majority of the fossils in Pleistocene deposits are indigenous to the Gulf (only 3% were from other localities). Almost all. o f these fossils are also found with large habitat ranges, covering the subtropics to the tropics. For example, three of the most common bivalves found in the Las Animas Pleistocene deposits, Chione californiensis, Chione undatella and Osirea pamula, are all found from. California to as far south as Peru. Fossil assemblages and biofacies determined by R- and <)- mode cluster analyses, group fossils into three main categories: sandy beaches, rocky shores, and tidal flats. These environments are commonly found along the modern gulf coast and near to the Rancho Las Animas site. For example, Puerto Balandra, located 25 km north of the La Paz, is an excellent example of a combination rocky shore and tidal flat/ mangrove environment. At Puerto Balandra, sediments are filled with corals, rhodoliths, and molluscan shells, much like the sediments found in Las Animas (Halfar et ah, 2000). Another example is the coastline adjacent to the Rancho Las Animas terrace, where rocky outcrops of the underlying Cerro Colorado Member provide adequate surface attachment for rocky shore habitats, while right next to the rocky outcrops lays sandy beaches. The similarities between modern, and Pleistocene molluscan communities indicate Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 167 that the molluscan fauna did not change much during the last interglacial. The biggest difference between Pleistocene and modern communities is the presence of large and extensive colonies o f P. panamensis. Although the genus Forties is found throughout the Eastern Pacific, it is only found as a major builder in the Galapagos Islands and in Panama. In the Gulf o f California, two species of Parties are present, P. panamensis and P. svedrupi. Neither o f these two corals are major reef builders in the Gulf today. Parties panamensis mainly occurs throughout the Gulf as small corals attached to rocks below the extreme low tide level (Brusca 1980). The only places today where P. panamensis is found as large patches in at El Pultno and Puerto Escondido (Squires 1950). At El Pulrno, P. panamensis is common in the deeper parts of the reef and in between the topographic ridges upon which the main reef is built. In Puerto Escondido, there is a thin persistent line of P. panamensis growing 2 meters away from the mangrove trees and no where else. Neither o f these modem day counterparts of P. panamensis growth are as abundant or extensive as those found in the Pleistocene deposits at Rancho Las Animas. So why did Parties panamensis grow in massive coral patches in the Las Animas area? The answer may lie within the corals. It is known that with corals there are several factors that are important in controlling distributions and species diversity. These factors include light, sedimentation, temperature, salinity, storms or wave energy, tidal exposure, nutrients availability, space competition, and grazing by herbivores, corallivores and boring sponges (Porter, 1974; Chappell, 1980; Huston, 1985; Spalding et al., 2001). Of these factors, high salinities and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 168 cooler winter temperatures are believed to be the cause o f limited coral growth in the Gulf o f California today (Reyes-Bonilla, 1993). I n general, corals require subtropical to tropical temperatures year round (14 to 30°C), and normal marine salinities (33 - 37 ppt). Coral can. live in the extremes o f these sea surface temperatures and salinities, but do not produce large growths or bioherms. In the Gulf o f Cal ifornia, the range of annual sea surface temperatures is large (10 - 32°C) in the southern tip, to about 1 .9 - 30°C in the northern part (Roden, 1964; Halfar et a i, 2000), Salinities in the northern two-thirds o f the Gulf range between 35%« and 35.8% <>. In the southern third of the Gulf, the range is between 34.6%o and 35%o (Roden, 1964). Because Pontes panamensis is found throughout the Gulf of California, it is possible to say that, P. panamensis can survive in a range of sea surface temperatures from 14°C to 32°C and salinities between 34.6%oto almost 36%o. B ut why did Poritespanamensis grow in such abundance while Pocillopora elegans, the main reef-builder in El Pulmo, did not? In most of the east pacific, both Pocillopora sp., and Porites sp. are found together in the same reef habitats (Brusca and Thomson, 1977; Glynn and Wellington, 1983; Reyes-Bonilla, 1993; Spalding, et a/., 2001). However, there are only a few areas in the modem east pacific where Porites sp. are the main reef-builders, the Galapagos Islands and off of the coast of Costa Rica (Glynn and Wellington, 1983; Spalding et a!., 2001). Large colonies and patch reefs o f Porites are found in the cooler waters off of the islands Isabel and Santiago in the Galapagos (Glynn and Wellington, 1983). Along Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 169 the coast of Costa Rica waters are also cooler (15 - 33°C), and are sites of frequent upwellings (Glynn and Wellington, 1983; Spalding et a l, 2001). Data acquired from studies done on Pocillopora damicornis in the Indo-Pacific, indicate that Pocillopora growth rates decline in latitudes with temperatures below 20°C (Harriott, 1999), and bleach when temperatures rise above 32°C (Berkelmans and Willis, 1999). These thermal limits for Pocillopora also occur in the Gulf of California where Pocillopora elegans only grows in the southern part of the gulf, where temperatures range from 19 - 30°C. It is possible that during the last Interglacial sea surface temperatures in the Gulf of California may have risen just enough such that Porites panamensis' growth rate increased to allow massive coral forms, w hile at the same time not rise enough to allow' for Pocillopora elegans to form large bioherms. With a rise in the sea surface temperatures, salinity may have risen as well, which may have also acted as a deterrent for Pocillopora growth but was still within the boundaries for P. panamensis growth. Another factor to take into consideration is sedimentation. Most massive P. panamensis bioherms found in the L as Animas terrace deposits appear to have formed first in channels that cut through the terrace. These channels would have been the sites for an increased sediment load in the currents flowing through them. Studies also preformed by Barnes a n d Lough (1999) concluded that massive Porites located off of the Coast of Misima Island, New Guinea did not alter in their response to increased sedimentation, and that only burial of the corals themselves hindered growth. So it Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.70 is possible that sites o f increased sedimentation, while may not have hinder the growth o f Porites, may have hindered the growth of Pocillopora. There are four reasons why Porites panamensis and not Pocillopora elegans formed massive bioherms at the Las Animas site: 1) Sea surface temperatures and insolation increased just enough to increase the rate of extension and calcification o f the Porites panamensis, while not increasing enough to promote the same in Pocillopora (Harriott, 1999; Berkelmans and Willis, 1999). 2) The increase in sea surface temperatures still maintained a large enough range in summer and winter maximums to keep Pocillopora from forming large structures (Glynn and Wellington, 1983; Berkelmans and Willis, 1999; Spalding et al., 2001). 3) Sea w ater salinities values either maintained or increased from present day values to allow Pontes panamensis to form massive morphologies, while hindering Pocillopora (Reyes-Bonilla, 1993), and 4) Areas of increased sedimentation, such as the terrace channels, hindered Pocillopora growth but not Porites, allowing the Porites panamensis to become established and out compete Pocillopora ( Barnes and Lough, 1999). So how did the sea surface temperatures increase to allow massive growth forms o f Porites panamensis! With the growing precision of the U-series dating (Gallup et al 1994, Stirling et al 1995, Stirling et al 1998, McCulloch and Esat 2000), it has become more apparent that the rise in sea level during the late interglacial may not have been caused by Milankovitch forcing but occurred several thousand years before the insolation peak. These studies suggest that the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 . 7 1 insolation peak in the southern hemisphere occurred at 137 ka, several thousand years earlier than in the northern hemisphere. The increase in southern, hemisphere summer temperatures may have led to an increase in the northern hemisphere winter temperatures by increasing the heat flux to the north, through Hadley circulation (McCulloch and Esat 2000). This increased in the northern hemisphere winter temperatures would have made the ice sheet in the north unstable before the onset o f the Milankovitch insolation peak. New studies such as those by Muhs, et al. (2002a,b) and Fen burg and Goodwin (2002) suggest support for this idea, however it remains controversial. Fenburg and Goodwin’s research on late Pleistocene corals (Porites panamensis) from Punta Bajo in the Gulf of California, suggest than winter sea surface temperature were 2.4°C warmer than today. A problem with their study is the poor preservation of the corals at Punta Bajo may not have yielded reliable results. All these studies however, help to explain the large growth of Porites panamensis at the Rancho Las Animas area. Since P. panamensis is adapted to not only cooler temperatures, but also a larger range in . seasonal temperatures than other corals found in today in the Gulf, a summer temperature value comparable or only a couple of degrees more than to today with an increase in winter temperature can help explain the dominance and larger growths o f P. panamensis at the Rancho Las Animas terrace segments. Add to this the 97% o f late Pleistocene fossils found at Las Animas that are indigenous to the Gulf today, and it is possible to see at late Pleistocene Gulf with the same or Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 172 warmer winter temperatures as today before the northern hemisphere insolation peak. T errace Depositions! Paleoenviromnental Model The Late Pleistocene deposits at Rancho Las Animas demonstrate a depositional cycle o f transgression and regression in the last interglacial. A basic model o f the depositional history of the Rancho Las Animas area can be made from this study to rebuild and describe the paleoenvironments. Before the sea level rose, the region around Rancho Las Animas was probably much like the modern topography, with occasional Miocene ridges stretching out to the coast. Because the highest points on Km 26 Terrace segment are only covered with a thin layer of beach gravels, it was probably the highest point in the shoreline topography. The shoreline terrace was repeatedly cut forming channels. As with the area today, these channels were probably cut by storms and flash floods. As sea level rose, basal conglomerates, oyster beds and reworked sands from the Cerro Colorado Member were deposited across the landscape, filling in the channels, and forming a paleoembayment that stretched from south o f Rancho Las Animas to E l Coyote. Fossil assemblages from these deposits indicate species .from both rocky and tidal flat environments. Sediment analyses also indicate that these deposits were deposited under low ? to moderate energy currents, with very few sediments coming from the Miocene mountains in the west. With the transgressing sea and possible increasing sea surface temperatures, Porites panamensis flourished, first attaching Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 173 to the floors of the small deeper channels and then later to the tops o f the terraces. Once P. panamensis established itself, it spread across the sea floor in large coral thickets, growing into targe branching colonies as the sea level increased to its maximum. Strong storms occasional hit the paleoembayment, breaking and redcpositing P. panamensis on top o f the old colonies where new colonies would eventually grow. Fossils from these deposits were filled with rocky shore inhabitants, who probably attached themselves to the corals. Grain size analyses indicate that these large coral deposits were also sites o f varying degrees o f current and/or wave intensities, with, little or no volcanies from the western Miocene mountains. Sediments consisted of two different populations, one coarser grain size consisting of fragments of corals and shells and a second very fine grain size possibly deposited by eolian forces. As sea level decreased, so did the size of the P. panamensis, smaller finger sized forms o f P. panamensis flourished along with rhodolith beds and indigenous molluscans. These deposits are very similar to those found in the La Paz area today, they consist of molluscan assemblages of rocky shore, sandy beach and tidal flats, with lagoonal and mangrove elements. Sediment analyses indicate current and/or wave energies from very low to high, and up to 50% o f the grain samples containing volcanies from the Miocene escarpment, implying a decrease in the sediment formed from biogenic sources and an increase in deposition from the western mountains. In regards to the areal distribution of the deposits, rocky shore fossil assemblages of these deposits are more common in the southwestern parts of Animas North terrace segment and the Dune terrace segment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174 Sandy shore and tidal flat fossil assemblages o f the coral, molluscan and rhodol ith biofacies are com monly found in the north part o f the Animas North terrace section, the Km 26 terrace section and in the flat regions to the north (i.e. Road Cut, Road Pit, Potrero, and El Coyote). Small faults formed, cutting through, and between the terraces, possibly forming small hydrothermal seeps such as those found in Bahia Concepcion (Greene e t a l , 2002). Rhodoliths arid corals finally retreated as the sea level became too shallow, and nearshore sediments and beach gravels soon covered the tops o f the emergi ng terraces. These deposits contain the highest percentage o f Miocene volcanies (50%), implying that these deposits were close if not at the shore where heavy minerals M l out o f suspension. Subsequent sea level drops deposited fanglomerates on top the western sides o f the terraces. Faulting continued, rising and gently tilting the terrace above the current topography, where erosion due to storm events cut the terrace into smaller segm ents. Lastly, modern coastal dunes covered the terrace tops. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 175 CHAPTER 9 Conclusions 1) There are several different facies at the Rancho Las Animas Terrace Segments, identifying the stages of a trangression-regression cycle. These facies (named for dominant characteristics) are called Basal Conglomerates, Fossiliferous and Reworked Cerro Colorado Member Sands, Large Corals, Pon tes, Molluscan and Rhodolithic and Sandy Marls, Fossiliferous Sands, Beach Gravels, and subfacies of Oyster Beds and Mounds, Small Pocillopora, Encope Sands, and Storm Layers. 2) A typical stratigraphic transgressive ~ regressive cycle appears in the field as Fossiliferous and Reworked Cerro Colorado Member Sands, Large Corals, one or more of the subfacies from Porites, Molluscs and Rhodolith Sandy Marls, Fossiliferous Sands and lastly, Beach Gravels. 3) G rain Size Analyses indicate several deposition dynamics. First, sediment w as deposited from two different localities, transported either from alluvial/run off, winds, reworked sediments or was internally deposited (e.g., sediment formed from shell, coral fragments). Second, depositional energy or current activity was highest for all coral facies and lowest for Encope Sands, Rhodolith and Molluscan Sands and Reworked Cerro Colorado Sands. Third, terrace deposition energy or current activity was h ighest at the Dune Terrace segment, lowest at the Km 26 Terrace segment Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 176 and variable at the Animas North Terrace segment, implying that the brunt o f the sea energy came from the north. This may have also implied that the Dune Terrace segment to the north and the Animas North Terrace segment to the south may have buffered the energy received at the Km 26 Terrace segment in the middle. And lastly, sediments of volcanic origin increase with the end of the regression, implying the approach o f the shore. 4) The U-series TIMS ages from the Rancho Las Animas terrace deposits are sim ilar in precision and overlap U-series ages reported by other authors for late Pleistocene terrace deposits on the eastern Baja California peninsula. Ages for Rancho Las Animas terrace deposits range from 108 ka and 209 ka, averaging 150 ka, suggesting that they correlate with the late interglacial high stand. 5) U sing the current height of the Large Corals facies and the U-series TIMS ages, uplift rates of 8 to 15 cm/ka were determined. The uplift at Rancho L as Animas is similar to other localities in the Baja California region (e.g. th e ten-aces at Isla Carmen is at +25 m and El Bajo in Loreto is at +16 in). 6) Molluscan assemblages determined by R- and Q-tnode cluster analyses indicate three assemblages: Sandy beaches, Tidal flats, and rocky shores. Included are also the subenvironments lagoonal, mangrove, and rhodolith beds. All of these env ironments are represented in the modern Gulf of California Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 177 7) Molluscan fossils from the Rancho Las Animas terrace deposits represent species and genera indigenous o f present day Gulf o f California. Only 3% o f fossils found are from warmer temperature regions. Distributions of these fossil, assemblages also indicate that a majority (>70%) of all genera/species are from a widely distributed area, 'thriving from, the subtropics to the tropics. This implies that if sea surface temperatures did change the .fossil assemblage would probably not, 8) The major difference between the paleoenvironments .reflected in the Rancho Las Animas terrace deposits and the modem, environment in the Gulf o f California is the presence of large branching growth forms of Porites panamensis. These large morphologies o f P. panamensis found in the late Pleistocene terrace deposits along the eastern coast o f the Raja Peninsula are not found in the Gulf today. Since this species of Porites is adapted to not only cooler waters but also a larger range o f sea surface temperatures, it may indicate that both the late Pleistocene winter and summer temperatures may have increased, but the temperature range remained the same. This rise in the seasonal, temperatures without a change in range would have allowed the thermally varied Porites panamensis to dominate the coastlines instead o f Pocillopora elegans with its smaller seasonal thermal range. Other factors such as increase in salinity and sedimentation may have also played a role in the dominance of Porites panamensis over the modern day dominant Pocillopora elegans. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 178 REFERENCES Applegate, S.P., 1986. 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Earth and Planetary Science Letters, v. 160, p. 745 - 762. Szabo, B.J., Ludwig, K.R., Muhs, D.R., and Simmons, K.R., 1994. Thorium-230 ages o f corals and duration o f the last interglacial sea-level high stand on Oahu, Hawaii, Science, v. 266, p. 93 - 96, Valentine, J.W., i960. Pleistocene molluscannotes, 3. Rocky coast faunule, Bahfa San Quintin, Mexico. Nautilus, v. 74, p. 1 8 -2 3 . Valentine, J.W., 1980, Camalu; a Pleistocene terrace fauna from Baja California. Journal o f Paleontonlogy, v. 54, p. 1310 - 1318. Valentine, J, W.f 1989. How good was the fossil record? Clues from the California Pleistocene. Paleobiology, v. 15, p. 1989. Veeh, H.LL. 1966. Th230/U2 3 8 and U2 3 4 /U2 3 8 ages o f Pleistocene high sea level stand. Journal o f Geophysical Research, v, 71, p. 3379 - 3386. Verrill, A.E., 1864. List o f the polyps and corals sent by the Museum of Comparative Zoology to other institutions in exchange, with annotations. Bulletins o f the Museum of Comparative Zoology. Harvard, vol. 1, p. 29 - 60. Verrill A.E., 1866. On the polyps and corals of Panama with descriptions o f new species. Proceedings of the Boston Society of Natural History, vol. 10, p. 325 - 357. Verrill A.E., 1869. Synopsis o f he polyps and corals of the North Pacific Exploring Expedition, Madreporaria. Proceedings o f the Essex Institute, vol. 6, p. 83 - 100. Verrill A.E., 1870. Review o f the corals and polyps o f the west coast of America. Transitions o f the Connecticut Academy o f Arts and Sciences, vol. 1, no. 6, p. 337 - 558, pi. 9. Wells, J.W., 1933. Corals of the Cretaceous of the Atlantic and Gulf coastal plains and interior o f the United States. Bulletin of American Paleontology, vol. 18, p. 83 - 292. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 189 Woelkerling, WJ.„ Irvine, L.M., a id Harvey, A,S., 1993, GrowtMorms in non- geniculate coralline red algae (Corallinales, Rhodophyta). Australian Systematic Botany, vol. 6, p. 277 - 293. Woodroffe. C.D., Short, S.A., Stoddart, D.R., Spencer, T., and Harmon, R.S., 1991. Stratigraphy and chronology o f late Pleistocene reefs in the southern Cook Islands, South Pacific. Quaternary Research, v. 35, p. 246 * ~ 263. Woods, A. J., 1980. Geomoiphology, deformation, and chronology o f marine terraces along the Pacific coast o f central Baja California, Mexico, Quaternary Research, v. 13, p. 346 •- 364. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A p p e n d ix A ...................... 1 ....... ; Latitudes and Longitudes of R ancho Las Anim as Sites Site | L a i Degrees | Lat. M in u te 1 Lon. Degrees j Lon. M inute DIM ■ 24 32.9591 110! 44.815 D1S2 .1 ........ ..... '" ”24 ..... 32.992"!....... " " " n o " ' " " " 44.782 D1 S3 .......24' ...........3 2 .9 7 9 t'''''"'''"'"''"'' n o ..44.747 ............ J" " " " " " " " " " " " " " " " " ...... 24 '"32.965]"'” .... ..........n o ]........ 44.747 D1S4 .........24 """ 32.975!....... .........n o ]....... 44.736" D1S5 .........24' ........... 32.928! . M O 44,744 i 24 ...........32,935]"'""...... 110 44.753 1)1 S6 .........24 ...........32.932"; 110 44,774 D1S7..... |........ ........24 32.906 n o . 44.82 D1S8.....j.." " " 24 ]]]'''"]"""'"'"32'"9lf']]'']]]]i n o 44.83 1 .....'.24 32.929 n o ..44.817 D1S9 ........24 32.947 n o ’ ..44.792' DISK) .........24 ...........32.893"|....... n o 44.703 D ISH ....... 24 32.876 n o 44.737 i .........24 32.874'] n o 44.719 ----------1 .... . 24 '" " ..........32.868! n o 44.702 D1S12 24 32.856 no] 44.6% D1S13 i 24 32.8411 110! 44.733 D2S1 1 24 32.825........ "Tiol...... 44.709 D2S2.. ...|~...... 24 32.778 n o ; 44.672 D2S3..."]." .........24 32.7371 i1o'T ........ 44.663 D2S4”...1 .... 24 .......... 32.679!'"...... n o ! 44.673 D2S5 ! ........ 24 32.567! 110! 44.65 D2bf 24 32.54]....... ......... u o j......... 44.65! D2S7 ; 24 32.531 i .... .........n o ]........ 44.621 D2S8 I 24 32.488: n o ! 44.63 D2S9 .....24 32.515! n o 44.559 D2S10 1 ...24 32.458! llOj 44.627 D2SlT j..... ..24 .........31443] 110! 44.609 D2S12...|... ..24 .......... 32.464]........ ........ " i io ..." " " " ..44.585 D2S13 24 .......... 32A29! I 10 ..44.535 D3S1......[ ........ ".......24" ]]]]]]] 32.534] ]]]]] ..... '..no"!........ ....44.69 D3S2.....! .... '.. ......“" 2 4 32.392] .........no]......... ..44.486 D3S3~ .....'"'24' ...........32384']........ ........ iTol........ ..44.468 D3S4.....1 ...... .........24 32.365!....... ..“ .....n o]........ ~ 44.417 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Append*! A Continued ; i Site ; L a i Degrees * 1 >at. M inutes, Lon. Degrees ' I *«». Minutes D3S5 24! 32,381; 110 44.394 D3S6 24! 32.304! 110 44.398 D3S7 24 32331; n o 44.361 D4S1 24! 32,427; 110 44.593 D4S2 24! 32.442: no 44.432 D4S4 241 32,298! n o 44.135 D5K1 74: > | 32.846; 110 44.631 1)582 24 32.935! n o 44.664 1)5 S3 24! 32.973. n o 44.659 D5S4 24! 33.029 n o 44,631 1)585 24 i 32.954! n o 44.606 D5S6 24 i 32.913! no 44.593 D5S7 24! 32.941 110 44.548 D5S8 24| 33.025 n o 44.553 D5S9 24' 33.047! n o 44.457 D5S10 241 33.012} 110 44,433 D5S11 24 32.977 n o 44.466 D5S12 24 j 32.851 n o 44.25 D5S13 24! 32.6491 110 44.293 D5S14 24! 32.644 i n o 44.366 D6S1 24! 33.535! 110 44.747 D6S2 24 i 33.488 n o 44.634 D6S3 24 i 33.613! 110 44.526 1)684 24! 33.69! 110 44.299 D6S5 24 33.82 n o 44.057 D6S6 24, 33.7031 110 44,016 D6S7 24 j 33.637! 110 44.041 D6S8 24! 33.511! 110 44.112 D6S9 24| 33.655! 110 44.801 D6S1.0 24 j 33.702 110 44.721 D6S11 24* 33.73 110 44.784 D6S12 24! 33.782! n o 44.761 D6S13 24; 33.9011 n o 44,753 D6S14 241 33.919! n o 44.702 D6S15 24) 33.829; 1.10 44.699 D6S16 24j 33.772; 110 44.705 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix A Continued | Site Lat. Degrees ;Lat. Minutes 1 Lon. Degrees iLon. Minutes D6S17 2 4 3 3,755]...... n o ..44,686 D6S18 ........ 2 4 33.617 110 44.649 D6S19 ............ 2 4 .33,6 1...... 110 44.66 D7S1 .......... " " " '2 4 33.865 n o 44.727 D8SJ ." " " " .2 4.......... 3 4 .2 4 " ]...... n o 4 4 . i d b s? . .............. 24 34.218 110 44.0./5 D8S3 .............. 24 34.178. 110; " " " " " " 4 4 . 5 8 5 D8S4 24 34.255 1 iO' .44.462 D8S5 ........... " " .24 34.198 n o ; 44.426 D8sr> 24 34.! 95 110 44.371 D8S7 .............. 2 4 34.255]......... 110. 44.337 D8S8 .............. 2 4 34.336 n o 44.318 D8S9 24 34.447 110 44.193 D8S10 24 34.404 110 44.535 DBS 1 1 .............. 2 4 .........3 4 .4 4 8 " !...... 110 44.553 DBS 12 24 34.478: n o 44.678 DBS 13 24 35.644 n o 44.794 DBS 14 24 36.4611 n o 44.654 DBS 15 2 4 36 .6 5 4 i n o 44.619 D9S1 .............. 2 4 .........34.227]...... 110 44.622 D9S3 ......2 4 34.195 110 44.66 D9S4 24 34.209 j 110’ 44.725 D9S5....... 24 34.307 110 44.721 D9S6 ......................24 .............34.382.......... 110: 44.734 D9S7 ......................24 ............. 34381] 110 44 6 4 1 D9S8 ......... 2 4 34.336; 110; 44 6 5 5 D9S10 24 ............ '34,267] .Tioi....... 44.657 D9S11 24 34.978 1 1 0 ! 44.404 LAS-01... 24 32.263 110 ...44.313 1 A S-02 24 32.2641 no, ...4 4 7 3 1 3 IAS-03 24 32.264 no 44.313 LAS-04 2 4 32.264 ....i'loi.......... ..44.313 LAS-05 2 4 32.264 110! 44.313 LAS-06 2 4 3 2 .2 6 4 ] n o f 44.313 LAS-07 2 4 32.264" ..... 1 1 0 ;" 44.313 LAS-09 2 4 32.869; 110 ..... ..— __ L 44.691 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 193 A ppendix A Continued ■ j Site !L»t Degrees iLat. Minutes i Lon. Degrees jLon. Minutes LAS-10 241 32.87) 110 44.692 LAS-1 1 24' ...33.792 j ..... 110 44.08 LAS-12 ..............24"..' .... 33.791 110 44.08 D12S2 24 34.486) 110) 44.702 D12S3...1 ... 24 34.818 n o 44.614 D12S4 .............24 j . . . . . . . . . . . . 34.849 no 44.577 D12S5..." ] " .... 24“ 33.629' 110 44.423 1)12S6 .............24;....... 34.168 110 44.383 D13S1 ■ 24 34.412: 110 44.443 1)13S2 24 34.424 110 44.365 D13S4 24 .....34.54' j]...... 110 44.509 D14S1 I 24! .3 4 ^ 5 ’ 110 44.558 D14S10 24 33.714 110 44.656 D14S11 24 33.79' 110! 44.696 D14S12 ■ " " " ...24)........ 33.883 110 44.735 D14S13 24 33.955 110' 44.803 DI4S14 ........... 24]........ 33.594'! 110 44.474 D14S15 24 33.588' 110 44.447 D14SI.6 .............” 24]...... " ...33 "592)' 110 44.431 D14S17 24) 33.621 1101 44.408 D14S18 24 33.593 n o 44.38 D14S19.| ... 24 33.618 1101 44.268 D14S2 ! 24: 34.439 110! 44.542 D14S3 1 24; 33.8 110 44.766 D14S4 , .............. 24" )....... ..33.812)......... 110! 44.806 D14S5.1 .... 24, 33.75) .......I'io j......... ..44.805 D14S6 | 24! 33.733 ...no]..... . -"44.782 D14S7 I 241 33.677 s ..no]...." " ... " ....44.7' D14S8 ..............24 r ...... 33.593) 110) 44.678 D14S9 ...... ~ ......24!........ 33.692 110 44.701 D15S1 241...... 32.339' 110 44.162 D15S2 ! 24'"""".. 32.382 no; ..44l()8 D15S3 ! 24' 32.358 .......I'l'ol.......... ..44.231 D15S4 24! "'"32.347]......... n o 44.23 D15S5 j 24) . . . . — . - - - I . . - — ... ..32.332"!......... 110; 44.291 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 194 O : oi o J o o o. iH, o io o o O ' ioj CM o © ! o ' © j o © I© >v 5! l i |S - |! s S l |. s! m i lit; « * a! 6 om-% Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. o o © [ © o iO © o o 11 o © © 'o\ ■ O : os :© © o ■o > 1 ■ © IO to o 2 k O j o o © o o jO o O; o so o lO « : i 5 i i e i s t g i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 196 O jo j O o so iO jO [O ■o o io! o , C i o o jo o ' o io o o o io o o o o o i>i"s S I I I I ! # R * O iO ip O s I t s . a . < m £ \k k \ n i l Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 197 O O o o ©i © j .©j . © i ® i ® ® ]® m C l ©i ® j© © © i I© © © © l © © © Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix B C ontinued site(T#j i : : : : a u : « : Family Cardita Cardita affirm Cardita ^ a jj Cardita radiate _ _ __ Jfamjly Subtotal = = ; 0 0 Family Chaaid a e' ~ Charm s g . ________ 3 Chamqjrondosa _ Clmma sguanmligem _ _ _ ; . ___________ Family Subtotal^__ 3 _ 5 Famijf Lucinidae Codakia sp. __ _ Codakjqdfftmgumda Ctena mextcam _ DnaUngqebimma Pffadngaperparvuia______ Lucimjtg_ _ Lucina canctilmis_ _ FamilySobtottd f ; 0_ j 0 Family Corbtdidae _____ Corbutasp. _ _ __ FamUv Dipiodoatidae Dipkffhnta obliqua______ Diplodonlajprteaia _Family Subtotal^ 0 • • _0 FaBulyJ>OBMidae Dornx gracilis Family Gjycymeridae Glycymeris sp. __ Glycymeris maculate Glycymeris gigamea__ _J f a n i g s « h ^ i _ = i o o __ hogtmomm chemnitztemis Isogfmonum Jams Family Subtotal =: 0 i 0 Family Cardiidae ' Laeyicardiwmelatimt Laevicardatm elemme T7 ’ TS T V lift Hi SIS i 1 6 T22 S 3? 2 z r r ~ ~ r~ ~ ~ t ~ z t ' - j ~ t ~ j~ ~ [ ”F 3 I'Io T ir^ T Z " C T 'lL 'T '~ o 2 ^31!~ ~ ~ z r z i z r 2 * r z™ ~~ z z z ! i ~ z z ~2 o 1 . 2 o * i ■ ! (i a r ; i ' ~ " i p~ .I r. " " ...~ i r ’ o' I o' ~ T " 2 ' ' ~ r ~ ~ Q ” |— -g f g - -r - p — p~ ....... ZZZZZZ p.Z Z IZ Z T ’ T “ o _ r "o’ : i t t r " i " i w p ........ , ................ , ...... p _ ................ ::z:izzz:::zzzzizz“ zn:zzzzzi::z_ :rzz:;z:zzii IZIIZ'ZIXZZZ! PZIZ'CZZ! i:ZZ5!ZI :EZIZ:I!IZEZ!!j ' 0 I ~ ~ ~ Q ~ .........p - p - N © oe 199 o[ : '0 ; o io :o o | : 9 * ^ )o o o ■ o o o| lol o 'o O j o ; o j O O f I O Oj ® ■ o ■ o o oj oj jo ol o jo o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 200 m o o o o o j o I I Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 201 © © © » m o o o , o o © © © © © © © i si I l i l i i | i ! li Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20.2 ;0 :»!§* O o ol ,o 5 0 cs o; o ; o o o io o o; : O O . o o io o' o j ® j Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 203 < s > l o o o fO : o c ? ;C ' o o o o o o o o o ;o o H o o o o o o o © : \tu 5 * S i i | M ( ! ' • § ! Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 204 f ym* ■ C l o jo .o! j O ; Oj ,O i io os o © ; © o ; o o ! o o ©. o o © W, j >4 & § 1 S| S i i i i i i i mail Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 205 ; O o o O ;o; o o tn\ o o o o ® o o o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 206 ® ® C f o O o O ® O o © 1 ® ® Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. A p p en d ix B C o n tin u e d ......................i _ Trigoniocardia bianguiita T37 ; T38 ; T39 | H I T43 ’ T ....P 144 14! J5 3 : T 5 4 J _T55_ ; TS6_ j TSS r m m Tr-achyaardhmi sp. \ i i i ! Trachycardium crnsors Famitv Subtotal =! 0 i ” 2.. " ! o t... ..i.....P " o ..r 0 “ P ' o ' T 0 ...0 1 0™T..T ...r " o “ Family MyUMdae ....... _ ^ M odiolus capax ' ..-......... b --- -4.....—- f - ---- ~ — ...-4— ------- — ......... I - ..... -...j- ----- -------- f---.... 4........- ..4......— Family Subtotal = ; 0 i 0 i 0 ! 0 0 i 0 I 0 0 : 0 ! o : 0 : o Q ! 0 Family Nucaliidae t Nucuta declgvis \ 1 Family Nnculanidae N uculam sp. : 2 f Nuculana elem m is | Famitv Subtotal = ; 0 i 0 i 0 ! 0 2 i 0 i 0 0 0 : 0 : 0 : 0 0 : 0 Famijy Ostreidae Ostrea so. i i 1 ! 3 ! Ostrea tiskeri O.iv t j pulv.ida I O st> ea % espenina ________ Family Subtotal ^ _ Family Pteriidae 1)_ _ L 0 |... 1 _0_ J_.....J L . . . P _0__[... ..._ _ 4 J ...J _ _ 0_ _ L 0 ; _0_ J Pinctada sp. Pinctada masallantica Family* Subtotal =; o : 0 ; o i 0 0 i 0 i 0 0 0 0 : o : o i (J : 0 Family Piiinidste Pinna rugosa ; -........—f- — -j----- f - -4-— ------ h ------ --------f. - .......i........... b .....— r ....— ........- j ...- 4 — ... Family Spondyttidae Pticalula anomiodes ' ■ 1 Plieatula im za m Piiccaula spondylopsis 1 ---------- 4-------- [ — 4 — --------- b _ i.. ...... - ....b ------- ~— ... — ... •- T " l... •--------- j ------- Spondyhts sp. ; Spcmdylus calcifer \ I Family Subtotal =i 0 0 ! o' f 4 1 l 1 0 : 0 ! 0 o : i 0 ; 0 Family Semelidae : Semeie bicolor \ -— ...4 — -4.. — \ - ---- -------- j.,.. - - 4 .. ..... - i. ..... - i-----b ..— 4 -... J — ..j-..... Sem eleflovescem ! Family Subtotal = i “ o'.... r “ o. 'T ...F T " "o '. . . .. f~~ '" o . . . . . . r " 1 " . r ~ o “ T "o~ . . r ‘I T .. .. . o ~ , .... p ....g ... Family Gastrochaenidae ! I Spengleria truncata 208 < N f'O s.Z , I 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. .209 III a;!!?!!! l;a Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 210 | c 4 i « 3 o ; O ? O i >O j jO j I C I S 1 o i o s ^ w ! * > ;oj * ■ « * < . | t | so- o " C * IO oi H!Q g o O | :o 'o’ © ! §11* I l|i i f i l H i l l l l S | | S iiia ffl • f 3 ; - t s ; - " 2 j ^ S ! i S i £ i i : t t ! 1 ^ ; a j y i ■ O S 1 *; k?! §5 2 ! i 5*1 $ * * f r®' J ? * J V ; J ^ i „ S ( R $ « 8 L C S t J 2 > S i « B s ■ > • ; > ■ > s J * i J C Q h W I Q j O j , . . . _ f e 1 O j w j _ Q | W . j ^ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21! r\ e > o o o o o o ' O o o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 212 O o o o o !o o o o o ® o ® o i o o M i g i S i f f i l S i S ! fa j j Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 213 © © © © © ;© © © © © ■ e s © © © © Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 214 O O © © © © o o :o © o o o © © © © © © © © © Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 215 O o: !o O i loi .o o o o ’ o .o o io p :0 ' ,o o o io > 0 . o !o| jo o o ;0 O ; O i o I o io o ; |o O ! oj o oi ol Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 216 O c * o o Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21? © © © '• < I © © © o © © ri Reproduced with permission of the copyright owner. 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A p p e n d i x C Las A n im a s Fossils' Distributions a n d Environments 1 \ Species Distribution En viroaments Gastropods Family Acroaeldae -j-..... ........... ...................................... ............ 1 ----------------------------- -------------------—...- ...-..— .—....... j« . . . - ........... . _ - . . . — Acmaea stipulate Collisella acutapex [Nicaragua to C olumbia SGulf o f California (On rocks ....................... On rocks at midtide level Collisella strongiana G ulf o f California On rocks at midtide level Family Arehitectouickiae Arckitectonia nobilis G ulf o f California to Peru rid J fiats to 36.5 meters Heliacm mazatlantica {Mazatlan, Mexico Fam ily Cerithiidae Cerithium maculosum G ulf o f California to Tres Marias Island, I Mexico Cerithium mcaraguese Nicaragua to Ecuador intertidal to 36,5 meters Cerithium stercuscarum 1 .ower California to Peru sand flats and estuaries Cerithium gemmation Lower California to Ecuador offshore Family Conidae Corns purpurascem Lower California to Ecuador tide pools and rocky ledges Family C a lf ptraeidae 1 Crepidula excavata ! Lower California to Panama on other shells Cmcibulum seidettatum 1 Lower California to Ecuador Ion stones, shells, intertidal mud flats to 27 meters CrucHndum spimsmn j California to Chile on stones, shells, itrtertid&lly to 55 meters Fam ily C ypraeidae i Cypraea anmttae Guff o f California under rocks and in crevices; intertidal to subtidai Cyprea robertsi !Gulf o f California to Peru lap to 18 meters Family F issarelliiae I ! Subfamily Diodorinae 1 Diodor a alta SLa Paz, Mexico to Galapagos Islands Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix C Continued Species i Distribution i Environm ents Diodora imequolis (Lower California to Galapagos M aids j under rocks; intertidal to sabtidal Diodora satumatis Lower California to Ecuador Fam ily Hipponix____________ FamUy T o a n id a e ^ " Malea ringem 1 California to Peru iMazatian, Mexico to Peru jintertida% ________ ____ __________ (rocks and sand bars Fam ily Mitridae Mitra catalinae Family Moduiidae Modulus cerodes i G ulf o f California to Panama mudflats Family M oricidae Subfamily Muricinae j Murex elmesis IGuIf o f California to Ecuador itttertidaliy o h rocks to shallow subtidal Muricmfhws nigritus JGulf of California on reds and tidal flats Fam ily Nassariidae ! Nassarius gemmulmm j Acapulco, Mexico to Panama i seaftoor or fidal mud flats Mmsarim tiarula jGulf o f California to Panama seafloor or tidal mud flats Faintly Naticidae Natica chemnitzii SLower California to Peru niterltdal on mud flats Natim elertae Lower California to Ecuador up to 36.5 meters Polinices recluzianm Gulf o f California to Tres Marias Island. sand bars Mexico Fam ily Nerltidae Nerita fimiculata Nerita scabricosta Fam ily OJividae Lower California to Peru Lower California to Ecuador on recks mteitidally on rocks intertidally Oliva incrmsata L ower California to Peru sandspits at extreme low tide and intertidal to Oliva polpasta Lower California to Ecuador subiidal in sandy regions low intertidal and subtidal sands Oliva splendidula Tres Marias Island, Mexico to Panama ta ivj -a Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. A ppendix C Continued Species 1 D istribution Olmspkata i Gulf of California to Panama OliveUa alba {Lower California to Acapulco, Mexico Family Vermetidae Pesaimmhm indentatm iGutf o f California to Central America Petalconchus complicatm ■ Panama Petalconchus contortus j G ulf o f California to Panama Petalconchus flavescem jGuaymas to Mazatlan, Mexico Serpubrbis margaritaceus (Gulf o f California to southern Mexico Familv Strombidae j Strombus gracilior 'G ulf o f California to Peru Strombus granulatus {Gulf o f California to Ecuador Strombus gpamdatus subsp. aeutm I Family Terebridae I Terebra melia {Panama Terebra variegata {Gulf o f California to Pern Terebra strigata {Gulf o f California to Panama Family Thaididae | Thais biserialis {Lower California to Chile Thais speciosa {Lower California to Pern Family T arbinldae Turbo fluctuosus Lower California to Pent Turbo saxosus Gulf o f California to Peru Turbo squamiger i G ulf o f California to Peru Fam ily Turriteiikfae Subfamily Turritellinae Turritella mariana Gulf o f California to Colombia Turitella nodulosa Gulf o f California to Ecuador Environments _________ intertidal to subtidal sands intertidal to subtidaf sands isand fiats and muddy lagoons tip to ■ 45_meters I beaches o f rock and sand upjo 6 1 meters up to 22_ meters___________ _____ buried in intertidal and subtidal sands on rocks intertidally on rocks between tides among stones intertidally among rocks intertidally below low tide level {between 2 2 - 14? meters {between 4 -1 7 0 meters Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix € Continued Species D istribution ! Environm ents Divalinga perparvula {Gulf o f California to Acapulco, Mexico • Lucirn cancellaris ! Lower California to Panama [between 7 to 73 meters Fam ily Dipiodoatidae Diplodofita obliqua Diplodottta sericaia ! Lower California to Ecuador [California to Ecuador [between 7 to 24 meters .... ............. ........ intertidally or 7 to 73 meters on sand or mud [bottom Family Doaaeidae Donax gracilis [Lower California to Peru intertidal iv to 24 meters Family Glycym eridae Glycymeris metadata [Gulf o f California to Peru [shallow to deep waters Glycymeris gigamea [Gulf o f California [between 7 to 13 meters Family Isognonj&ntdae \ Isogonomon chemnitzianus {Lower California to Chile [attached to rocks, intertidally or in shallow waters Isogonomon jam s [Lower California to Oaxaca, Mexico i Family Cardiidae Laevicardium elatum [California to Panama [mudflats Laevicaniium eleneme Lower California to Ecuador lup to 92 meters Trigoniocardia biangulita L alifomia to Ecuador intertidal to subtidal sand and mud up to 46 [meters Trachycarditm comors Fam ily Mytilidae 'G ulf o f California to Galapagos Islands [tidal flats to 46 meters Modiolus capax Fam ily Naculiidae [California to Pern intertidally on rocks or mud up to 46 meters Nucuta declevis [Sonora, Mexico to Panama [between 7 to 55 meters Family M acalanidse Nuculana elenemis [Lower California to Ecuador [between 4,5 to 82 meters ta O ' Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix C Continued Species • > Distribution Environments Fam ily O streidae Ostrea fisheri Gulf o f California to Galapagos Islands attached to reefs and inside caves between 3 to 61 meters Ostrea palmula | Lower California to Galapagos Islands attached to mangrove roots, rocks or reefs up to ? meters Ostrea vespertina j Lower to Upper Pliocene Family Pteriidae i Pinctada mazatlantica [Lower California to Peru subtidaliy attached to rocks between 3 to 61 meters Fam ily Pinnidae Pinna rugosa [Lower California to Panama partially buried in sand and rubble or mud attached to rocks; interttdaily to subtidal up to 30 i meters Family Spoadylitdae Plicatula anomiodes ! Guaymas to Mazatian, Mexico attached to flat surfaces on rocks Plicatula inezana (Gulf o f California to southern Mexico Plicatula spondyiopsis Spondylus cakifer iGulf o f California to Panama [Gulf o f California to Ecuador attached to rocks interidally to subtidal up to 18 meters: also found attached to coral head at Ei Fam ily Seraelidae -4...... ....— ----- ------------ ------------------- ---- ■ ... Pultun Semeie bieoior [Gulf o f California to Panama Semele flmescens Fam ily Gastroehaenidae Spengleria truncate Family Sanguinolariidae Tagelus qfftnis ! Southern California to Peru [Mazatlan, Mexico to Panama [ Gulf o f California to Panama intertidally boring into other shells mudflats up to 73 meters Fam ily Telltoidae Apofymetis cognata clarki IGulf o f California to Acapulco, Mexico -...—----------- -------- --— ------------- -- -..-......— Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix C Continued * Species Oistribution Environments W lim sim ukm Ljwer California t o P e r u intcrfidally to 24 m e t e r s Strigilla disjuncla Family V enerkiae____ Subfamily Chioninae Chione califoriemis (Nicaragua to Panama mtertidally to IS meters ] California to Panama iiatertidaily on mud flats mid ofshore io m , ers on muddy bottom Chime eompta j Gulf o f California to Peru offshore between 22 to 28 meters Chione kelletii jGulf o f California to Panama offshore between 46 to 73 meters Chione guaiulcoensis (Port Guatulco, Mexico to Panama in 13 meters Chione undatella S Southern California to Peru sandy beaches and offshore up to 92 meters Chione lumens jGulf o f California mud flats and offshore Subfamily Dosiniiae Dosinia pmderma JGulf o f California to Peru j (offshore up to 60 meters Subfamily Meretricinae Tivela hvronensis ■Lower California to Ecuador (sand beaches and offshore to 73 meters Tivela arguta Tivela plamdata ! G ulf o f California to Panama (Gulf o f California to Ecuador 1... —------------------- ------- ------- ------------- ---------- Subfamily Pitarinae Megapitaria auraniiaea jGulf o f California to Ecuador i below extreme low' water level and offshore to 9 1 meters Megapitaria sqmlida I Lower California to Peru i sandy mad fiats also offshore to 161 meters Echinodenns Emope grrndis subsp, inezarta IGuif o f California Encope californica i Diadema mexicamm spines j G ulf o f California to Galapagos Islands rocky low intertidal Eucidaris thomrsii spines jGulf o f California to Panama rocks and reels at mid to low tide level to 275 meters Seaphopods Dentatium hamocki jGulf o f California to Colima, Mexico shallow sandy bottom to 73 meters Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix C Continued Species________ ____ ________ ipfetrtbufion _____ F m i a r i a s p k n d i d a j G ulf o f California to Ecuador C orals _____ ______ | _ _ Porites panamemis jG ulf of California to Ecuador Psammora stellata ______ jLa Paz, Mexico to Galapagos islands Environm ents _ _ intertidaliv and offshore in coarse sands to 200 m e te r s ._________ ___________ intertidal to subtidal between 1 to 10 meters Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Terrace Animas North_ _ _ _ _ _ _ _ _ _ Site [Height jFaeies S tratigraphy LofBedi _________ jtop ["Finger" Porites, Molluscan and I Rhodolith Sandy Marls '1.75 m Large Corals D1S2 top S a m e a sD lS l 2 m Large Corals D1S3 top Encope Sands DIS3.5 Jtffi... . . . I Rhodolith Mound \ Large Corals D1S4 [top Rhodoiith and Molluscan Sands 12 m Large Corals D1S5 ‘ ‘ Finger" Porites, Molluscan and Rhodoiith Sandy Marls D1S5.5 0.3 m (Large Corals ____ | Fossils [Chione califorimsLs, Serpttlorbis \sp,. Turbos saxosus, Strombus sp., lOliva spicata, Pyrem strombiformis, \Terebrasp„ Barbatiasp., Codakia |sp., Pinctada mmatlantica and \Donax gracilis, | PorBesjpmcmemis \Pqritesj>atmmemis Pectens and Encope sp fmcticose rhodoSMis Porites panamemis ■ Porites pammemis Porites panamemis \Porites panamemis Descriptions eroded top with scattered shells, shell fragments and rhodolkfas bottom boundary bidden byjalus^ bottom boundary hidden bv talas ...... _ ........ -------- t t .,... ......-------------- _ s ______ .... This site is i.22 m hi^ier than DfStandDIS2_________ M ound 0.5 as in diameter bottom boundary hidden by talus bottom boundary hidden by tatas corals thin out and dissappesr here; green sands from €etro Colorado jV fta, are .present___________ ___ __ bottom boundary hidden by talus; loose basal conglomerates are interbedded with the corals and talus; conglomerates are brown to > cllowish orange and vaiy severl cm ■ to.size__________________ ________ Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Continued Site D1S6 ! Height Fades Stratigraphy _ [of Bed ________________________ 1 1.75 tn Large Corals 1 | Rhodolith sad MoUusean Sands 1 Fossils \Porites panamemis. pimtada Imamtlantiea Descriptions D1S8 1 i Large Corals iPorites panamemis D1S9 | ‘Rhodolith Mound mound §.58 x 0.63 si; Balk Sample T66 D1S11 i 1.24 m Large Corals IPorites panamemis bottom boundary hidden by talus D1S1 i,5 <2.44 m "Finger" Porites, Molluscan and ; Rhodolith Sandy Maris i Large Corals IPorites panamemis \ Porites panamemis bottom boundary hidden by talus D1S13 Rhodolith and Molluscan Sands i \ top five layers alternate between rhodoliths and molluscan sands and thin fragmented rhodoliths layers i ; Rhodolith and Molluscan Sands Rhodoliths and Ostrea sp. ' • ........... ......— ---- -------------- 1 m Rnodolith and Molluscan Sands |0.' ii Rhodolith and Molluscan Sands ‘Reworked Cerro Colorado Member Rhodoliths, Eneape sp., Serpvlorbis sp., Oliva sp., Chione sp. „ and _ Pectens^____ Rhodoliths and burrows _ _ j bottom ‘Cento Colorado Member | j Rhodolith and Molluscan Sands — ................-... .— ....-......- • —....— occasional finger size P. panamemis D2S2 | ‘Rhodolith and Molluscan Sands occasional finger size P. j I Rhodolith and Molluscan Sands ---------------------- -- -------------- - panamemis ...... ........ .......... ....... occasional finger size P. panamemis D2S4 ‘Oyster Mound Ovtrea palmula mound 0.7 m in diameter to U J Vj Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Continued S te ; Height I Facies Stratigraphy _________ {of Bed j___ D2S4 | Rhodolith and Molluscan Sands Continued 1 _ _ _________ D2S6 10.6 m Encope Sands 10.6 m Encope Sands |0.6m Encope Sands ©2S7 jtop Fossiliferous Sands j7.3 m 'Large Corals D2S9 ; 10.3 m ; Large Corals Fossils j Descriptions 14 Chione califoriemis, 1 Oliva fossil count from a I sq, ft. area; this spicata, 2 Cerithium nicaraguemx, 2 Tagelus peruviantis, J Semeh •flavescem, 2 Strigilia lenticuia, 1 Diodor a inaequalis, 5 Encope sp.. and rhodoliths 3 Encope sp„ 2 Chione califoremis, and rhodoliths ________________ 14 Encope sp, Fragments, J Tell'mn sp., 2 Argopecteneircutaris, 2 Chione califoremis. 1 Telraclita sp . Porites panamemis fragments, fructiose rhodoliths, and several burrows ________ _ _ _____ Chione spStrom has sp., and Pinctadammadmtica ___ Forties panamemis _ Porites panamemis, 3 Pintado mazatlantica, t Chama \ ) uamuligera, 6 Isogonomon ^ emnitzianm, 1 Chama sordida, and several sea urchin spines site is located on the arroyo floor 10 m from the raised Pleistocene terrace deposits; this sand fa r is 1.8 m in height and several meters in length area fossil count from a 1 sq. ft. fossil count from a 1 sq, ft, area bottom jwm idary hidden by talus corals are infilled with sands and shells; horizontal corals and nibbles can be seen; three Bulk Samples were taken, the first 2 m above talus, the second at 2.3 m, the third at 2.5 m; first balk sample had a fossil count from a 1 sq. ft, area Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Continued Site ’ T ~ D2S11 Height Facies Stratigraphy o f Bed ____ 1 |2.5 m_ ! 0.4 m ; Basal Conglomerates D2S12 D3S2 S am easD 2S ll D4S2 D3S5 I j m !0.7m [0.2 m 15 m _ [thin Large Corals Basal Conglomerates Cerro Colorado M e m b e r ___ Large Corals_ Rhodolith and Molluscan Sands D3S5 Continued | thin Coarse pebbly sands [0 J m Small Pocillopora D5S2 D5S6 bottom jCerro Colorado Member^ ^ L 5 jn [Large Corals top _ [Beach Gravels _ _ _____ thin ; Rhodolith and Molluscan Sands [Fossils IPoritespanamemis \ Porites panamemis \ Porites panamemis IPorites panamemis Porites panamemis fragments and molluscans_________________ Pocillopora sp .. Ostrea sp,, 8 Chione califoremis, 1 Isogonomon chemnitziamis, I Encope sp., 1 Pinctada mazailantica, and 1 Pocillopora sp. Descriptions conglomerates are brown, orange and buff in color_______ I conglomerates disappear o.. casional patches o f jum bled corals conglomerates vary in size from several cm to 20 cm and in color ft cm brown to buff to .green [at die bottom o f this sail are small branching Pocillopora sp. ; unit is interrupted with horizontal storm . layers__________ _____________ angular cobbles from underlying Cerro Colorado; fossil count from a ! sq. ft. area Porites panamemis_____________ j bottom boundary hidden by talus Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Continued Site Height Facies Stratigraphy _ _ .....- i . _______________ _______ _ _ D5S6 0.6 m [Large Corals Continued 1 1 'Fossils \Porites panamemis I Descriptions j D5S7 stop Beach Gravels 5 1 Ithin Rhodolith and Molluscan Sands ; 10.6 in Large Corals IPorites panamemis i I D5S8 I to p Beach Gravels i j ithin Rhodolith and Molluscan Sands ? 1 i0.6m Large Corals IPorites panamemis 1 D5S9 itop Beach Gravels | ithin Rhodolith and Molluscan Sands 1 10.6 m Large Corals IPorites panamemis D5S11 )0 J rri |2 m Beach Gravels \Poeiiopora sp, fragments Rhodolith and Molluscan Sands : Chione sp.t Anadara multieosta. P. I panamemis fragments, and \Pocillopcra sp. fragments i tbodolitfis large and irregular 1 !0.6m Large Corals 1 Porites panamemis J D5S14 Beach Gravels | ithin Rhodolith and Molluscan Sands |0.5 m "Finger" Porites, Molluscan and Rhodolith Sandy Maris ‘ .Porites panamemis ; corals up to 20 cm in height j | 0 / ii ^torm Layer small stubby P, panamemis and rhodolith fragments ]!.? in Reworked Cerro Colorado Member Porites panamemis and bivalves ithin storm layers present in S is unit j D15S1 'top Rhodolith and Molluscan Sands : 1 Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. A p p e n d i x D Continued Site [Height Facies S tratigraphy ! o f Bed [Fossils j Descriptions D15S2 DI5S3" [top Itop "Pencil" Porites and Molluscan Sands Beach Gravels \Chiom sp., Setpulorbits sp j Trigonicardium bimgtdim, Pocillopora sp. And P. panamemis [fragm ents____________________ __ D 15S4____[top _ T errace tan 26 Cerro Colorado Member J ---------------- -------------------------------- --— --------------------------------------------- D6S5 Corro Colorado Member D6S6 (Top Cerro Colorado Member s iFossiliferous Sands D6S7 Itop Fossiliferous Sands D6SS M ! s; a I 1 .... 1 .....i....in i* ? ..................... i [Large Corals Cerro Colorado Member 1 «siliferous Sands ' ’urge Corals P. panamemis. Plimiula inezana. Pmctada mmatkmtica, Diodora inaeqnalis, Serpulorbis sp., Isogonomm chemnitzimus, and Barbatia reeveama. [corals green [occassional storm layer: corals beads up to 5.5 or in height j~i m ; Reworked Cerro Colorado Member ■irchitectonia placentalis. hogonomon chemmuimm, and ut chin spines D12S5 (1.2m [Large Corals P. panamemis D14S14 |2 cm [bottom (top Osyter Mound Cerro Colorado Member Beach Gravels Ostrea palmula [red-brown cobbles 3-4 cm in [diameter Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Continued j Site Height -Facies Stratigraphy ! Fossils -Descriptions isfB ed DI4S14 ;2.13 m 1 Large Corals P. panamemis Continued D14SJ5 i~S cm ; Rhodolith and Molluscan Sands i 1.2 m Large Corals \P, panamemis D14S17 ~5 cm Beach Gravels bottom Cerro Colorado Member D14S1S top Cerro Colorado Member D14S19 ,5 cm Fossiliferous Sands jl-5 nt Large Corals IP . panamemis (bottom Cerro Colorado Member D6S12 16,5 m s Large Corals j P. panamemis, Pimtada occassional storm layer; corals mazailantica, Chione tumem, [ heads up to 0.71 m in height; Bulk ISemele bieolor. and Dminia sp., an J Sample taken I Rhodoliths -0.5 m j Reworked Cerro Colorado Member 1 3 Isogonomon chenmitzianus, 3 .fossil count from a 1 sq, ft. area \Twbo squamiger, I Chione sp., i ! Anadara sp., 3 Astrangia sp., and 1 Rhodoliths D6S13 |5 J m 1 Large Corals P. panamemis bottom boundary hidden by talus; fossils similar to those found in Site D6S12 D7SJ (4.9 m 'Large Corals \P , pammemis bottom boundary' hidden by talus; rbssils similar to those found in Site D6S16 j6.7 m Large Corals } ’ panamemis bottom boundary' hidden by talus; fossils similar to those found in Site D6S12, D6S13 andD 7Si D6S17 'top Fossiliferous Sands -burrows 0.5 cm diameter barrows Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. A p p e n d i x D Continued Site (Height (Facies Stratigraphy (Fossils Descriptions (of l e d D6S18 (top "Pencil" Porites and Molluscan \CMomsp., Barahatio sp., Attack- B ik Sample T83 takes here Sands \sp„ Terehra sp., Poliniees sp., IPorites panamemis, and i Pocillopora sp. ................... ......... ....... ................... (2.3 m Large Corals \P. panamemis ________ _ _ ................... .... D14S8 "Finger" Porites, Molluscan and Porites panamemis, Pocillopora sp., Rhodolith Sandy Marls \Chionesp., and Rhodoliths D une T errace D8S1 4.4 m Large Corals \P. panamemis Basal Conglomerates C erro Colorado Member D8S2 (top Oyster Bed \Ostreapalmula D9S1 (4.5 m (Large Corals \P . panamemis (bottom boundary hidden by talus D8S3 (top (Beach Gravels I Chione sp., Anadara multicosta, m i ( cobbles up to 5 cm in length ; Trigonicarium biangulita i2 m (Large Corals P. panamemis !2m ("Pencil" Porites and Molluscan Pintada mazmlamtica, Anadara sp.. (Sands Tr igonicarium biangulita, Chione sp., Barabatia sp., and P . I (bottom Reworked Cerro Colorado Member j'Pcinatttettsts Pocillopora sp. bottom boundary hidden by talas D8S4 (0.45 H i '’Finger" Porites, Molluscan and . Porites panamemis, Pocillopora sp., bottom boundary hidden by talus \ Rhodolith Sandy Marls Twritelia sp., Pincmda sp., ] \Pinctada mazailantica, Pectens, and (Rhodoliths DSS5 \3 m Large Corals \ Forties panamemis, Pimtada several small mounds on the arrows mazatlantica, Ostrea pcdmula, and floor .Barabatia reevearma ta Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Continued Site ‘ Height Facies Stratigraphy iofBetf ; (Fossils Descriptions D8S8 D8S9 ~ D8SJG 1 1 ip ~ .....m ni Oyster Bed _____________ L irge C orals_______ i irge Corals I Ostrea palmula __________ [P. panamemis_______________ \P. pammensis, Ostrea pamula, \Pimtada mmatlantica, Spondylm \cdeifer, Chama sp., Pectess and (urchin spines bottom boundary hidden by talus D9S2 itop Beach Gravels (cobbles up to 7 cm In length (3 si) Large Corals IP . panamemis bottom boundary hidden by talus D9S4 (3.9 m Large Corals \P . panamemis bottom boundary hidden by talus D9S5 D9S6 (1.5 m Large Corals (Fossiliferous Sands \P.jpanamensis (bottom boundary hidden by talus i3,3 m i Large Corals S P . panamemis 1 bottom boundary hidden by talas D9S7 j*3L__ (Beach Gravels (Large Corals P. panamemis bottom boundary hidden by talus D9S8 !3 as ‘ Large Corals P. panamemis (bottom boundary hidden by talus D9S10 14 m Large Corals \P. panamemis (bottom boundary hidden by talus D12S2 13.9 jrt Large Corals IP . panamemis (bottom boundary hidden by taitts D12S6 1 1.5 T il Beach Gravels (shell fragments (cobbles up to 4 cm in length 11.5 m Fossiliferous Saids iChimesp,, Oliva sp., cobbles b o larger than 3 cm in \ Trigonicardhtm biangulita, and \ Anadara multicosta length ranging in colors from red to 1 brown are present (4 m "Pencil” Porites and Molluscan Sands iChiomsp,, Chama sp., TmriteUa \sp„ Serpuiarhis sp., Ostrea pamula, IPlieatula inesana, Spcmtfylm \primeps, Strombm sp., Turbo \squamiger, Pectens, and Parties s i vanamemis |3 ai Large Corals P. panamemis (bottom boundary hidden by talus ts* Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Appendix D Continued Site (Height j Facies Stratigraphy _ _ j o f B e d j _ _ DI4S1 12 m (Large Corals D14S2 (top (Large Corals Descriptions P, panamemis, Ostrea pamula, bottom boundary hidden by talus Pmclada mazatlmtiea, and Chione P. panamemis bottom boundary hidden by talus; smail mound 3 m in height and 6 (meters in length on the airoyo floor 244 Appendix E. Schematic Drawings of Rancho Las Animas Terrace Segments. DIS1 D1S6 * * • * * , # * • vu_ Nil j D2S6 » k o : [ s «w D1S2 \ Ax» A J— j T4 14 DIS? D2S7 D m d i sh * • * W 4 I 3 - J 1 D1S4 E S 3 • y A'»i *- D1S5 "TP H D1S13 b < 5> i * ■ D2S4 5 g F D2S8 « ^ « a D2S9 D2S11 \ 1 T r - c ? f P o l!!k.ll W W W M I « Stratigraphy of Terrace Segment Animas North Sites. Legend on Figure 42. Height of Stratigraphic Sections are approximately I meter between side bar ticks. Unknown contact heights are represented by dashed lines. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 1 Continued Stratigraphy of Terrace Animas North Continued. D2SJ3 T k -A- { * — J I't D3S2 “ f -------- « T r J D3S4 l c d c d * • * * T S P g g # t s .D3S5 b n N D4S1 " o m •m D4S2 r c D5S2 n D5S3 N p y ^ v e » M W ^jp® . »WW A M 1 sm M M i t WH ^ o II Y ' D 5S 8 D5S9 « b w « m i s s M t f c * D5S11 MS D3S7 t 1 \m m m m D5S6 » » i * i D5S14 E E w^rjw Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix E Continued Stratigraphy of Terrace Segments Animas North and Km 26. D15S1 D6S2 M ,* ‘ »* *i * ‘ J . . ». D65L" ^ r n n D15S2 M H M ( M l B M 1 2 s t I S W f t S D6S4 W : D6S16 rf n n ' i i D.15S3 O ' L -o r- D6S6 W g ? " D6S18 T * 1 1 1 1 D6S? I D7S1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24? Appendix E Continued Stratigraphy of Terrace Segments Km 26 and Dune. D 6 S 1 2 D 1 4 S 8 D 1 4 S 1 4 D 1 4 S 1 5 D 1 4 S 1 6 j am I ^ ' i f c \ J ftW i p n am m* - I ' L ____________ m> * ! I J D 1 4 S 1 7 D 1 4 S 1 8 D 1 4 S 1 9 . 0 1 2 8 5 O l .......................\ \ i ) 4 l im - S - - M tfiJ m ..... -mimm ... . . D 8 S 4 D 8 S 5 D 8 S 8 D 8 S 9 | I S ': : 1 c r w ” ,» " ' S ' V 1 8 J V 0 8 S 1 m j f I < 3 , / \ I 4 J < 3 < 3 1 | - j D B S 1 0 \ am saa N ? ' I . s \ ' D 9 S 1 D 9 S 2 D 9 S 4 \ - \ x: ' .........V : ..........y * ..... m m J L m m sm m m m w» i _ - m — •m am 4 i ' - Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A ppendix £ Continued Stratigraphy of Terrace Segment Dune Continued. 248 CD CD < X C D \ \ 6 \ j d i D9S10 D9S6 < 3> \ D12S2 D9S7 . 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O * r > jO OiOjOv C v O v <s f-l v© cl »a. *r vo i »-• > ) * o ;ro (r, *n *r | » -h fiiri j m T t ! : < N I * iO O O ’O v n 0 0 W O | O IO S 0 0 i < N | V O jO |d|o £ « > -r i.... IfS lO iO v O S voioofdiovi1 '! C 1 1 nf | r * i t m;<N'* • * * < * * fvr,:vo I; I I P ' S OiO A A ■ A A A Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2S7 If- U ' NIC O S * r% rj !; t* V ® S O rs f r i [ r^ i » — sd;<m r - <Nt-^ ri* ! * N ,. ; a * r - > t > r - . S ^ 'S i ^ S S 2W, * r , * < * * • ; if'i r* v, ^ iri i f a t o V j < a » * n»‘® t-l 0 0 4 0 "T ^ v . w** ^ rn «t‘ i « * * S ’ DSD! a jS ( /* trt S 'S w to •o, * o v t » O I O', i V> fr 1 *t 'Vi n *8 £»$ :S0ifS so ! (* i) f f * > ! f * > i t*i v * * * i f’ T i ©O' < -■ ! 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Further reproduction prohibited without permission. 262 n Q fi « h s l r I r < - i * r i t ' w > i — ■ i i [ < r! © '< » , ' ! (-“'•n-fSi i ; i ■ : j i ’ i> ~ O ' f t . s o o \ * ~ I-' I ® 5 S r v » (o i o\ i o ! j ; I j ... I >0} -f « + ig IS ys; # 2 .( ■ » .! fri: p I & s' D g l « , !*§ £ I * 2 % . \0 fi j H h s l^ J? fe? > i^iJS > $ s C " ! j Cl | i Q fbo (iS I'M © If* !<N U O : > j © 0 1 N D I ■ f t' j O j c * i ! * - < r* i ioo * m > O , i O 'tfi&s C « * 00 s?:s « ? < n f* < N «Tl i M 0 "* < i!' f i % 6 O j f <"! i t f 0 ;0i* 5 f v ° ;rO j ■ < W t ....f ...... o * * - v * i i* a < n‘< n « f(i^ ^ *n( i- ^ ^ ^ < £ > 1 * n - v. » n ? i C\ f } m * O ) r4 O O i Cn : * •* \ 0> ■ ■ * -* !tn i/! CmS * ° ’o o O i ^ t - tf\J oo;*ri[«5i^in^ ;$ V i 0 v IKI * T f'iH ^ • * “ * ? ; C * > f - r > O O M O V i r * > c * r-ii^ * i r i o i. w i t* < O i o n o o P S P ' £ Cj;0 ^ V i n r<\ 0 vo o ci I* . 0026 ! 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O' ’ t> C * fX f © d , - g ooif ltfr, *-* o o . v a •»f • ...I.... j!» D ^1 1 Is as !i s p n r-i 1 v * j s o r-(5 M rvl T; n . «SI i O , » * “ » * ^ , 3 “ ^ CM O ' «M, C 5*4 — - “ • • • -> | o (^ i * - * (w * ^ g £ s C * ^ * ^ 1 » A * /l O K — » * £ M O O 'O i'- * ©0 S©’^ o© g ^ -^OO^rM^r^OO^rCNC % J t ii^!voi-* t^.'C ^;orsO ;r^? osi S 55 m o Vi o>o i^6 r? C’l C M C M 00 SO O O *t ' t 7 (? - < 0 1/| V, (* - »o 0? «H| ^ 1 < t> I | o | o r i O «r. M ONjVOiCM sCM ICM i ^lol^iooioslesios! ; * a M n i ^ M 1 § S s . c S i w * s | i * r » o i ^ ■ c i C M g iO 'O 'r-ic^frV r-. «-o©l^ & 1 0 | ^ j ^ | 0 ; \ 0 ; ^ ^r- C S ? C O I ^ 1 m & ^ I *-* < r-1 V O i C O ; C M - O n S O i 0 0 ! ^ < 0 ? S O ’ oi^iooio, os;o%.,4 n r^ j i r^f f i , r i f i U N j l - d osleo <t w t-* »t — . d s i f o%l“t w o i** ( ' , ' ~ i v i o®1 o S; xt I T f1 M S: ■ s r i cn j '!" i 'O m <n — ' o . o 1 ^ o o o ? Reproduced with permission of the copyright owner. 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O iO iO IO M r^iO l'O IO j ' O 0 ,0 , s> c « J *- r*ii^f s i ( ; S 1 I i ! ; i i ( .....^ ] 00 i Os s V O ! “* * * m I tr\ | !00!O!V>‘«N!00;C r5 i 1 Gt\ < 1 Q \ : O S s 3 0 ; O s ? c v r e n ri r, r,|i* 4 ' i n *r> 00;-r o>1 1 « ? * < • : o o ~.<fr o v in; i O i: M — ' 6 * 0 !»>« M in -rf •+ • — f l ~T i Vs V, © ■ ©'© R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 276 E E E E E E E I V D *t tN t* *S © v li1 " • « " « M l I* © <«,r« If, " W * a * * H K (m ! 2 S * a s <C O ' ■ § ;3 O O JS* 4 X 3 C N s . M . s S ' m ■ V i 0 0 c2 O' , t * r -j, go*' la j? s* ..... sO rsi.pin tjr '7 7 “ ‘ r i n f - ; v d r i f f / OOIOICO ‘ | ( N j r * V O ? r * < n « b s : l O ' M v , -r -*• « * ’ uv® P o |( N J S . - f I V > j C T \ i © v i - • , * • ■ . £ } " > » : f r , t ' . 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M ; r- c * i O, <A, ‘O 0,00 i * • - * s * * « • ' r-\ • . c\ r-! r- x r , I"!,--; o -; lO S if 'lj'O f !r-» I» !s *i IPISlSI 4 d »■ 'O’ I > — *: f< • } s * « • * i I jsJ I < ! • # ■ > ; ^ | K fri v > & 3 .5 /3 i a ! i g s L M . X „ jsfcS 2;i iHi iO! rn j so j *-* i v% | «© |O fcK Wl — * r « j ■ • * * * ■ r-j •s s' 5. 1 . : f 1 r ^ ; * C S i.S P » - -015 m 4>;!? § i r ......... 5 i 5 - ‘* 3 I l u 5* o ! ■ ■ - ..... u i « s fe jH ^ .S *8 a r - o o ' * r sr^ o r£ ’ d i ° ; o - <r, > < • , ir, : r - s < N sq f ^ 3 | t> < q r* -1 in 1 . m — -t— - so o o tN r) K sx\ e m © sk; — i,0 1 o o '! •; d m ! < • < - ! . - f ' . j j f l " * n ;sr» i O I O ; fW \ R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. ! i % n 278 Appendix G Rancho Las Animas Grain Size Frequency Graphs Grain &vm Frequent# vs Weight Percentage of Sample T53 4$ si m . Grain Size Phi Grain Sfce Frequency vs Weight Percentage o f Sample T54 Grain Size Phi Grain Size Frequency vs Weight Percentage of Sample T55 . . . 4 1 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 279 Appendix G Continued Chain Size Frequency vs Weight Percentage of Sample T56 ! H»-r M . i- i i ! ■4 ■ 2 0 Grain Sis® Phi 2 4 6 rain Size Fk .„ J Weight Percentage of Sample TSi I Grain Size Pi Grain Size Frequency vs Weight Percentage of Sample T59 1 0 0 -6 . 4 0 Grain Size Phi 2 4 6 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Weight % I | Weight % W eight* Appendix G Continued 280 j Greta Size Frequency v* Weight Percentage o f Sample I'hO -6 -2 0 2 4 6 Grain Size Phi On n S./. I . jquency vs Weight Percentage of Sample TO ■ 1 0 ■ Grain Size Phi j Grata Size Frequency vs Weight Percentage of Sample T62 —20 9 * — Grain Size Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 281 Appendix G Continued * & i Grain Sim Frequency vs Weight Percentage of Sample T*3 (jraio S ijK C F»ti • ! . . Grain Si® Frequency vs Weight Percentage of Sample T64 IS tS go i f 20-+ ■ 2 0 2 4 6 Grain Sis® Phi Grain Si® Frequency vs Weight Percentage of Sample T65 f ■ m A •2 0 2 4 6 Grain Si® Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 282 Appendix G Continued <3r«*n Sis* Frequency vs Weight Percentage of Sample T66 -6 -4 - 2 0 2 4 Grain Size Pin ! ' Grain Sstie Frequency vs Weight Peicentuge of Sample T67 ■ 80 i ; Grain Size Frequency vs Weigh! Percentage of Sample T68 ± ,4 , Grain Size Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 28.3 Appendix G Continued Gram Size Frequency vs Weight Percentage of Sample T69 * ; I ; i • L . l | | r .^ !a l...-iir | i .....g | ( tV Grain Size Phi - 4, Grain Size Frequency vs Weight Percentage of Sample T70 40..f -6 - 2 0 2 4 6 Grain Size Phi i Grain Size Frequency vs Weight Percentage of Sample T71 -6 A - 2 2 4 6 Grain Size Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Weight % I { Weight % Appendix G Continued 284 | Grain Size Frequency vs Weight Percentage of Sample I /2 i ! j j , ... h »6- t - - 40 Grain Sisse Frequency vs Weight Percentage uf Saiuple T75 -* 0 - ■ 2 0 2 4 6 Grain Size Phi Grain Size Frequency vs Weight Percentage of Sample T76 40 - ( • > a ■ 4 • 2 4 6 Grain Size Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. W eigh? % 285 Appendix G Continued I drain Size Frequency vs Weight Percentage of Sample 17? \ ! m - \ .......... « 4 ........... - ......- ... i - I Grain Size Phi Grain Size Frequency vs Weight Percentage of Sample 178 8 0 O -6 -4 -2 2 4 6 Grade Mean Phi Grain Size Frequency vs Weight Percentage of Sample T80 IO 0 -6 ■ 2 0 4 6 tirade Mean. Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Weight % j j Weight % ' ■ Weight % Appendix G Continued 286 twain Suse Frequency vs Weigh! i'cioasiag© o f Sample T8t itKr -4 ■ 2 0 2 4 6 Grade Mean Phi Grain Sis* Frequency vs Weight Percentage of Vdtnpie I HI ...40 Grade Mean Ph Grain Size Frequency vs Weigh! Percentage of Sample 1 $3 j i -4 0 •2 4 6 Grade Mean Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. j | % !SP>3M j I % W SRM Appendix G Continued 287 m ain Size Irajuency vs Weight Peiwmage of Sample T84 60. 0 •6 -2 4 6 Grade Mean Phi f Grain Sias Frequency vs Weight Peic.riige of Sample T8S -6 -2 2 ( I 4 6 Grade Mean Phi Grain Stee Frequency vs Weight Percentage of Sample T86 -20 - 2 0 2 4 6 Grade Mean Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Appendix G Continued Grain Him Frequency vs Weight Percentage of Sample T88 , k> 0 - t i 8 ( 1 «! 0 -6 -4 2 4 6 Grade Mean Phi Grain Si*. i . -ju n cy vs Weight Percentage of Sample T89 60 i -6 -2 0 2 4 6 Grade Mean Phi Grain Size Frequency vs Weight Percentage ol S pi f90 ».© I 'I 20 •2 0 2 4 6 (ionic Mean PU i R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 289 Appendix G Continued Grain Sis* Frequency vs Weight Percentage of Sample T43 Grade Mean Phi Grain Sis® Frequency vs Weight Percentage of Sample T47 Grade Mean Phi Grain Size Frequency vs Weight Percentage of Sample T45 ■ — — ~ Grain Size Phi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Weight % j Weight % 290 Appendix G Continued Crain Sis® Frequency vs Weight Percentage of Sample T48 40 -4 -2 0 2 6 4 Grain Stee Phi Grain Size Frequency vs Weight Percentage of Sample 187 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission.

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Asset Metadata

Creator De Diego Forbis, Teresa Ann (author)

Core Title Paleoecology and depositional paleoenvironments of Pleistocene nearshore deposits, Las Animas, Baja California Sur, Mexico

Degree Doctor of Philosophy

Degree Program Geological Sciences

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag Geology,OAI-PMH Harvest,paleoecology,paleontology

Language English

Contributor Digitized by ProQuest (provenance)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c16-479080

Unique identifier UC11334939

Identifier 3133258.pdf (filename),usctheses-c16-479080 (legacy record id)

Legacy Identifier 3133258.pdf

Dmrecord 479080

Document Type Dissertation

Rights De Diego Forbis, Teresa Ann

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA