University of Southern California Dissertations and Theses

Cyclostratigraphy and chronology of the Albian stage (Piobbico core, Italy)

(USC Thesis Other)

Cyclostratigraphy and chronology of the Albian stage (Piobbico core, Italy)

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. 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 bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. in the unlikely event that the author did not send UMI 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. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. ProQuest Information and Learning 300 North Zeeb Road, Ann Arbor, Ml 48106-1346 USA 800-521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CYCLOSTRATIGRAPHY AND CHRONOLOGY OF THE ALBIAN STAGE (PIOBBICO CORE, ITALY) by Alessandro Grippo A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (GEOLOGICAL SCIENCES) August 2003 Copyright 2003 Alessandro Grippo Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3116705 Copyright 2003 by Grippo, Alessandro All rights reserved. UMI UMI Microform 3116705 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 OF SOUTHERN CALIFORNIA THE GRADUATE SCHOOL UNIVERSITY PARK LOS ANGELES, CALIFORNIA 90089-1695 This dissertation, written by AL6.SS/\NiD(k) 6&IFPO under the direction o f h '*S 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 o f the requirements fo r the degree o f DOCTOR OF PHILOSOPHY Director Date-----A u g u st-12.,—2QQi Dissertation Committee Chair Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ii ACKNOWLEDGMENTS This work would not have been possible without the help and contribution of many colleagues and friends; outstanding among them is the figure of my advisor, Alfred G. Fischer, an example under any point of view. I feel very lucky and honored to have met him and to have been able to work with him I learned from him under any point of view. I want to thank Timothy Herbert, then at UC San Diego in La Jolla, for suggesting me to meet and talk with Alfred G. Fischer. Linda Hinnov has been of invaluable help in introducing me to the world of Fourier analysis during an extended stay at Johns Hopkins University in Baltimore and in several other occasions in which we had the chance to meet. A substantial part of my work has been financed by ENI-AGIP in Milano, Italy, and I am grateful to all of the persons who made this possible, starting from Antonio Valdisturlo to Luciano Gorla and Maurizio Orlando. Steve Lund first introduced me to statistical analysis and helped me out in early attempts to use magnetic susceptibilty as an analyzing tool. Jurgen Thurow spent time with me discussing some aspects of image analysis, and the same did Graham Weedon about spectral analysis. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. iii Help came from discussions and conversations I had at various times with Donn Gorsline, David Bottjer, Gerald Haug, Douglas Sherman, Robert Douglas, Isabella Premoli Silva, Bruno D'Argenio, Lisa Pratt, Giovanni Napoleone, Elisabetta Erba, sir Nicholas Shackleton, Bernard Beaudoin, Walter Alvarez, Gian Battista Vai, Mike Rampino, Maya Elrick, Eugene Shoemaker, Christian Koeberle, Alessandro Montanari. Alessandro Montanari has been a splendid host in his facilities at Coldigioco, in Italy, where I stayed and worked during several productive summers and where I met a lot of interesting people. Stefano Cresta introduced Alfred Fischer and me to the beautiful Bugarone quarry that inspired the first serious attempt at the application of optical techniques at surface exposures Winnifred Fischer also has always been very kind and helpful to me, particularly in those days she and Al allowed me to temporarily stay at their place. Friends and fellow students have also been very important in increasing my knowledge and in discussions and I like to remember among them Cong Wang, Michael Neumann, Andrea Albianelli, Maria Rose Petrizzo, Arie Jan Doets, Inaki Irazabalbeitia. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. iv In these last years I have been supporting myself by teaching at Santa Monica College and California State University at Northridge. I would like to thank the people who made this possible: Janice Austin, Richard Robinson, George Dunne, and also Kathleen Marsaglia, Peter Weygand and Richard Squires. I wish to thank my parents, who always encouraged me in exploring my own ways and supported me in my whole course of studies. My father died a few weeks before I was accepted at USC and he would be very happy to see where I am now. Last but not least, Lorena Bignamini who, by being by my side all of these years, has been of great support, particularly with her decision to leave everything behind to follow me in this adventure, which proved to be very exciting and mind-opening for both of us. Early work on cyclicity in the Italian Cretaceous, including the drilling of the Piobbico core, was supported by the U.S. National Science Foundation. This and the Italian Consiglio Nazionale delle Ricerche supported the drilling and processing of the Piobbico core. Early studies of the core were aided by the American Chemical Society’s Petroleum Research Fund and the International Office of the National Science Foundation. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V TABLE OF CONTENTS ACKNOWLEDGMENTS ii LIST OF TABLES, PLATES AND FIGURES ix ABSTRACT xvi PREFACE xviii 1 INTRODUCTION 1 2 CYCLOSTRATIGRAPHY 6 2.1 The orbital theory of ice ages 6 2.2 Orbital rhythmicity in strata 7 2.3 Cyclochronology 8 2.4 Beyond chronology 9 3. ORBITAL VARIATIONS AND THEIR EFFECTS 10 3.1 Overview 10 3.2 Earth's orbital parameters 14 3.2.1 Primary orbital parameters 14 3.2.2 Secondary orbital parameters 14 3.2.2.1 Obliquity 16 3.2.2.2 Equinoxial precession cycle 18 3.2.2.3 Eccentricity cycles and modulations of precessional effects 20 3.2.2.4 Long-term changes 22 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. vi 4 GEOLOGICAL OVERVIEW 24 5 THE SCISTI A FUCOIDI IN THE UMBRIA-MARCHE AREA 33 5.1 Lithostratigraphy and sedimentation 35 5.1.1 Drab facies 36 5.1.1.1 Carbonate oscillations 39 5.1.1.2 Bioturbation 39 5.1.1.3 Precessional anoxic pulsations (PAPs) 40 5.1.1.4 Urbino anoxic event 41 5.1.2 Red facies 42 5.1.2.1 Condensed mudstones 43 5.2 Biostratigraphy 43 5.3 Diagenesis 44 5.4 Cydostratigraphy 45 6 METHODS: THE PHOTOSCAN APPROACH 51 6.1. Introduction 51 6.2. Digitization of the photographs 54 6.3 Cleaning and rectifying the image (Adobe Photoshop®) 55 6.4 Gray-scale scan (NIH Image) 55 6.5 Recording the results 56 6.6 Smoothing 57 6.7 Logs 57 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. vii 6.8 Spectra and tuning 58 7 RESULTS 59 7.1 Power spectra 59 7.1.1 Tuning 60 7.2 Precessional rhythm 63 7.2.1 Precession confirmed 69 7.3 Short eccentricity rhythm 72 7.3.1 Red shift 74 7.4 Long eccentricity rhythm 78 7.5 Longer periodicities 78 7.6 Obliquity rhythm 81 7.7 Phase relations 83 8 PALEOCLIMATIC-PALEOCEANOGRAPHIC INTERPRETATIONS 86 8.1 Drab facies 88 8.2 Red facies 89 9 GEOCHRONOLOGY 91 10 BROADER IMPLICATIONS 93 11 THE GRAY-SCALE SCAN APPLIED TO SURFACE OUTCROPS 96 11.1 Introduction 96 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. viii 11.2 Aalenian Limestone (Bugarone Formation) 96 11.3 Cenomanian Scaglia Bianca 97 12. SUMMARY AND CONCLUSIONS 104 13. BIBLIOGRAPHY 111 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. IX LIST OF TABLES, PLATES AND FIGURES Table 1 12-13 Earth's orbital parameters in terms of the planetary fundamental frequencies. Earth's axial precession rate is estimated at k= 50.4712"/year, which gives a frequency of revolution of 3.8944x10‘2 cycles/ky (i.e., a period of revolution of 25678 years). Subscript numbers identify the planet: 1 = Mercury, 2 = Venus, 3 = Earth, 4 = Mars, and 5 = Jupiter; for each of these planets, the fundamental frequencies gj indicate changes in orbital eccentricity and longitude of perihelion, and S j indicate changes in orbital inclination and longitude of the ascending node, for the ith planet (Laskar 1990). Labels Pi, P2, E, e i, e2, and 0 indicate major orbital components labeled in Figs. 6, 7, and 8. Plate I Albian strata in the Piobbico core. (A) photolog with stratigraphic depth; (B) Gray-scale log, a butterfly-plot mirrored on black: widens to white with carbonate content, constricts with clay and carbon pigmentation. Upper 5 m contain many small gaps in core recovery. Gap in cycle 19, missing pictures. Gap in cycles 21-22, section faulted out, representing ca. 2 m; (C) 406-ka eccentricity cycles, numbered from top of Albian downward; (D) nannofossil zones; (E) foraminiferal zones and sub-zones. Fig. 1 2 The Scisti a Fucoidi (A) "Contessa" Vispi quarry in Gubbio, Perugia, (B) detail from the Piobbico area, Pesaro-Urbino. Fig. 2 3 Index map Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. X Fig. 3 15 Cycle patterns of the orbital variations. The eccentricity pattern shows the interaction of the ca. 100 and ca. 400 ky cycles. The obliquity cycle remains fairly steady but has slowed down through geological time, along with Earth's spin. The precession index expresses the modulation of the precessional cycle by the orbital eccentricity and depicts the deviation of seasonality from an average state which would be a horizontal mid-line. In this cycle, the northern and southern hemispheres are 180° out of phase. Based on Fischer and Bottjer, 1991, from Imbrie and Imbrie, 1979. Fig. 4 23 Changes through time of orbital periods for obliquity (top) and precession (below); based on Berger etal., 1989 Fig. 5 25 Stratigraphic and tectonic synthesis of the Umbria-Marche sedimentary sequence, from Alvarez and Montanari, 1988. Fig. 6 37 Lithic phases, bioturbation, and inferred aeration states Fig. 7 38 Photolog and gray-scale log of a ca. 2 My section of core, comprising superbundles 12-16. Gray-scale scan shown as butterfly plot, from black in center to white (limestone) on margins. Numbers refer to superbundles (406-ky eccentricity cycles), numbered from top of Albian downward. The constituent bundles (95-ky cycles), lettered, a-d, are punctuated by single or groups of precessional black pulses (PAPs). Bundles b and c have become wholly confluent in cycle 13. For color, see plate I. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. XI Fig. 8 48 Chemical and color variations in an 8-m Piobbico core segment, showing the long eccentricity cycles (II, III and IV), short eccentricity cycles (a, b, c, d) and, enlarged, precessional cycles (1, 2, 3, 4, 5), as obtained through microdensitometry (left scan) and calcium carbonate content variation plot (right scan). Form Fischer et al., 1991; modified from Fischer et al., 1990. Fig. 9 61 Fine structure of selected 406-ky superbundles, tuned to same length, a- b-c-d, 95-ky cycles in ascending order. In superbundle 12, under some obliquity influence, all bundle boundaries are marked by black PAPs. In superbundles 13,14,15 , transitional to red facies, Precessional signals vary widely in amplitude and preservation, see text. Cycles 13 and 14, transitional to red facies, show precessional signals of low amplitude but high fidelity, and confluence of central bundles. Amplitudes are high but fidelity of preservation is low in cycles 8 and 10, reflecting a strong obliquity signal. In cycle 24 the precessional signal has been largely wiped out by bioturbation. Confluence of the b and c bundles is shown in cycles 13,14 and 24. Fig. 10 65 Comparison of the successive superbundle, signatures in gray-scale log, tuned to 406 ky cycle and numbered from top Albian downward. One 95-ky cycle has been added to the Urbino black shale (superbundle 27). two to the maroon shale of cycle 30. Fig. 11 67 Power spectra of full time-series. (A) untuned spectrum, referred to stratigraphic space. (B) spectrum tuned to 95-ky bundle. (C) spectrum tuned to 406-ky superbundle or its equivalent. E, predicted 406-ky (long) eccentricity rhythm, e, and e2 , predicted modes of the short (ca. 95-ky) eccentricity rhythm. O, predicted obliquity rhythm. P, and Pz predicted modes of the ca. 20-ky precessional rhythm. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. XII Fig. 12 68 Spectra of 1,200 ky segments (three 406-ky cycle equivalents) as recognized by 406-ky tuning, overlapped. Note the great rise of obliquity power in upper part of core, and the red and blue shifts in the precessional modes, e, modes of short (ca. 95-k) eccentricity rhythm. 0, P, astronomically predicted modes of obliquity and precessional rhythms. Fig. 13 71 Amplitude modulations of precession index. (A) precession components of the 406-ka tuned gray-scale scan (gray curve), from top of cycle 8 down, obtained by Taner bandpass filtering with a lower cutoff frequency of 0.035 cycles/ky, and upper cutoff frequency of 0.060 cycles/ky, with a cutoff slope of 10A 15 db/octave. The amplitude modulations were obtained by Hilbert transformation (black curve). (B) amplitude spectrum of the amplitude modulation series shown in (A). (C) theoretical precession index over the past 10 million years (gray curve), and eccentricity series (black curve); (D) amplitude spectrum of the eccentricity series shown in (C). Labels indicate periodicity in ka. Fig. 14 73 PAPs and the phasing of cycles. (A), gray-scale curve mirrored on black, yielding an image of carbonate cycles bounded by precessional black pulses (PAPs).. (B), the alternative, mirrored on white, yielding an image of cycles centered on PAPs. (C), statistical distribution of PAPs and grayed (PAP- inferred) couplets (precessions) in a stack of 26 406-ky supercycles. Incidence of PAPs in the first precession of each 95-ky cycle would be near 100% but for their absence in the red facies and for a reduction of peaks by a running 3- point average. (D), patterns of statistical PAP incidence, projected to 800 ky, and suggested phase match to eccentricity cycles. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. xiii Fig. 15 75 Red shift in frequency modes of short eccentricity cycles (e1 f e2 ) tuned to 406-ky cycle. E, the 406-ky cycle of eccentricity, is not well resolved in such short series. (A-D) power spectra for the four “ quarters” of the 10 My core series, tuned to the 406-ky cycle, (cycles 0-13. 14-19. 21-26. 27-31). (E) the sum of the above spectra; comparison of (a) the sum of the four quarter series; (b), the sum of the two half-series spectra; (c), the spectrum for the full series. The frequency modes of the short eccentricity (e) rhythm have been displaced to 100.2 and 132.9 ky respectively, but E, their difference tone, remains close to present value of 406 ky. Fig. 16 76 (A) an approximation of the "true" eccentricity, x(t)=sin(2rtt/406) + 0.9*sin(2itt/131) + 0.7*sin(2jtt/124) + 0.6*sin(2*t/99) + 0.9*sin(2jtt/95), with minima indicated every ca. 400 ky by heavy black arrows (top curve); the 406- ky component of the "true" eccentricity, i.e., sin(2_t/406) (middle curve), with minima indicated by dashed arrows; and the "true" eccentricity replotted (bottom gray curve) and compared to a "distorted" eccentricity (bottom black curve) obtained by tuning the "true" eccentricity minima to constant 406-ky increments. (B) the amplitude spectrum of a 10-million year long "true" eccentricity series (top curve), computed as in (A), of a 10-million year long "distorted" eccentricity (middle curve) computed as in (A), and of the eccentricity band of the 9.6-million year long tuned Piobbico series (bottom curve). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. xiv Fig. 17 79 Amplitude modulations of eccentricity. (A) short eccentricity components (gray curve) of the 406-ky tuned gray-scale scan, from top of cycle 8 down, obtained by Taner-bandpassing with a lower cutoff frequency of 0.007 cycles/ky and an upper cutoff frequency 0.0112 cycles/ky, with roll-off slope of 10*15 db/octave. Also shown is the amplitude modulation series (black curve), obtained by Hilbert transformation. (B), amplitude spectrum of the amplitude modulation series shown in (A). (C) theoretical short eccentricity components (gray curve)obtained by the same Taner bandpass applied in A, and the amplitude modulation series (black curve), obtained by Hilbert transformation. (D) amplitude spectrum of the amplitude modulation series in (C). Labels indicate periodicities in ky. Fig. 18 82 Amplitude modulations of obliquity rhythm. (A) obliquity components of the gray-scale scan (gray curve), from top of cycle 8 down, obtained by Taner filtering with a lower cutoff frequency of 0.018 cycles/ky and an upper cutoff frequency of 0.038 cycles/ky, with 10*15 db/octave slope at the cutoffs, and the amplitude modulations (black curve) obtained by Hilbert transformation. (B) amplitude spectrum of the amplitude modulation series estimated in (A). (C) theoretical obliquity (gray curve) and its amplitude modulation series (black curve) obtained by Hilbert transformation. (D) amplitude spectrum of the theoretical amplitude modulations of the obliquity given in (C). Labels indicate periodicity in ky. Fig. 19 87 Paleogeographic reconstruction for Albian time, showing suggested directions of monsoonal winds and of downwelling warm saline waters. From Herrle (2002), with permission. H - high pressure area, L - low pressure area. The star shows hypothetical location of studied sequence. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. XV Fig. 20 92 Albian cydochronology as deduced from the Scisti a Fucoidi - Scaglia Bianca sequence in the Apennines of Umbria and Marche (Italy). Observations mainly on Piobbico core, supplemented by data from outcrop (Herbert et al., 1995). Paleontology after Premoli Silva (1977) and Erba (1986, 1988, 1992). Length of Albian estimated at 11.9 ± 0.5 My. Fig. 21 98 Ammonite zonation, Photo Log and Gray-Scale scan of the Bugarone Formation. Fig. 22 99 Spectrum of the untuned scan of the Bugarone Formation, with the expected periodicities for the Jurassic Fig. 23 102 Photo Scan of the Scaglia Bianca Formation and raw Gray-Scale Scan and Spectrum of the untuned scan of the Scaglia Bianca Formation, with the expected periodicities for the Cenomanian. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. xvi ABSTRACT The Mid-Cretaceous deep-water sediments (coccolith-globigerinacean marls) of the Umbria-Marche Apennines (Italy) show complex rhythmic bedding. In 1982, the Piobbico core was drilled through the Aptian-Albian Scisti a Fucoidi Formation to test the hypothesis of orbital climatic control in the mid- Cretaceous. Early studies on the Piobbico core have been integrated in this work, through the development of a new optical technique that uses the color (reflectivity) as a proxy for carbonate and organic carbon content. This technique was used to yield a digitized and image-processed photographic log (photolog) of the Piobbico core. From the photolog, a gray scale scan was obtained in order to produce a continuous time-series suitable for spectral analysis. A drab facies in the Scisti a Fucoidi is interpreted as recording normal stratified water conditions, while a red facies as the product of downwelling warm saline (halothermal) waters. Both facies are pervaded by orbital (Milankovitch) rhythms. These reflect fluctuations in the composition and carbonate production of the calcareous plankton in the upper waters. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. xvii The drab facies is overprinted by redox oscillations on the bottom, including episodical precessional anaerobic pulses (PAPs). Contrasts between the individual beds representing the alternate phases of the precessional rhythm rose and fell with orbital eccentricity, in the classical pattern of Berger’s climatic precession or precession index curve, varyingly complicated by the obliquity rhythm. According to this, greenhouse oceans in general, and perhaps this area in particular, seem to have been very sensitive to orbital forcing. A count of 29.4 406-ky eccentricity cycles yields an Albian duration of 11.9 ±0.4 My. This method has also been experimentally applied, with good results, using surface exposures. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. xviii PREFACE This dissertation is the last contribution to a broader effort to understand cyclicity in sedimentary sequences that started about twenty years ago with the drilling of the Piobbico core; this work resulted in a manuscript, now in press, and that will appear within a special SEPM volume on cyclostratigraphy, by Alessandro Grippo, Alfred G. Fischer, Linda A. Hinnov, Timothy D. Herbert and Isabella Premoli Silva. This thesis is an assemblage of original contributions and sections taken directly out of that manuscript. I have personally developed the new approach used for image analysis, cured and completed the whole scanning, and performed all of the basic time- series analysis. In doing this, I enjoyed the indispensable supervision and experience of Alfred G. Fischer and Linda Hinnov's training in time-series analysis. A short addition on the application of these methods to surface outcrops was developed through direct observations of cyclic sequences observed during field trips in the Umbria and Marche Apennines. Experimentation with images has yielded good results in the Bugarone sequence, to which I was introduced by Alfred G. Fischer and Stefano Cresta, and in the Scaglia Formation, as observed at the Piobbico core drill site. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. xix Chapter 2 discusses the history and concepts of cyclostratigraphy, and the recognition of its patterns in the rock record. Most of what is written comes from the lessons learned in these years from Alfred G. Fischer's talks and writings; these are summarized in his introduction to the SEPM special volume in press on cyclostratigraphy, written together with Bruno D'Argenio, which constitutes the framework of this chapter. Chapter 3 is a short review of the astronomical signatures of sedimentary rhythms and is assembled out of previous literature, with the works of Hinnov (2000) and Floegel (2003) as main references. Chapters 4 and 5 describe the geology of the area and the stratigraphy and sedimentology of the Scisti a Fucoidi Formation; the bulk of the discussion is adapted from a field guide of the area published in 1992 by Elisabetta Erba and Isabella Premoli Silva. Chapter 6 is concerned with the description of the methods that I developed for this study. It was originally thought as an independent paper and then reduced to appear as an appendix in the above mentioned manuscript of Grippo et al., and subsequertly re-expanded to be included in this thesis. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. XX Chapters 7 through 10 constitute the core of the manuscript and include the results of the spectral analysis, their interpretation and a discussion on cyclochronology. Alfred G. Fischer has worked closely with me in the strategy and the tactics of presenting the data in figures and text, and in the interpretations. Linda A. Hinnov contributed to some sections of the paper: the quadrature analysis of the precessional cycle, some of the interpretation of the obliquity record, and the red shift problem with the eccentricity cycle. Chapter 11 is a short expansion on the possibilities of these techniques for surface outcrops, and is also part of the quoted manuscript. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 1. INTRODUCTION In the course of reading Earth history from the stratified sediments, the strikingly repetitive patterns in some facies were certain to draw the attention of geologists at some stage. At the end of the XIX century G.K. Gilbert suggested that these rhythms represent a record of orbital variations, and could work as a chronometer. At first geologists were not very responsive but eventually the existence of such pulse beats has become apparent. Nowadays they have become the standard for Quaternary history and they are continuously contributing to the refinement of older ages. This work is a small contribution in this direction. The goal of this investigation is to explore the cyclicities that pervade the Scisti a Fucoidi Formation (Fig. 1). The Scisti a Fucoidi consists of a sequence of pelagic Aptian-Albian marls and limestones exposed in the Northern Apennines of central Italy, in the regions of Umbria and Marche (Fig. 2). Cyclostratigraphic studies on this formation started more than 20 years ago, when deBoer (1982) and deBoer and Wonders (1984), established the limited surface exposures. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 Fig. 1 The Scisti a Fucoidi (A) "Contessa" Vispi quarry in Gubbio, Perugia (B) detail from the Piobbico area, Pesaro - Urbino Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 ACQUALAGNA 2km PIOBBICO LeBrecce core site ■ Monte Nerone CAGLI Bugarone quarry Monte Petrano ITALY nte Petrano section / CANTIANO m Fig. 2 Index map Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 In 1982 Premoli Silva, Napoleone and Fischer drilled the Piobbico core through the formation in order to establish the nature of the cyclicity and a geochronology (Tomaghi et al., 1989; Erba, 1988; 1992; Premoli Silva and Sliter, 1994). Herbert and Fischer (1986) and Park and Herbert (1987) tested two methods of study applied to a highly rhythmic 8-m segment of the core, representing about 1.5 Ma. One was a gray-scale profile of stacked multiple densitometer traverses of ektachrome slides. The other was a calcium carbonate profile, assembled from samples with a mean spacing of 2 cm. The resulting profiles showed the gray-scale scan to be a good proxy for calcium carbonate content. These studies confirmed the presence of the 100 ka short cycle of eccentricity (with its characteristic bifid peak) and also discovered the presence of the obliquity rhythm; at the same time presence of the 400 ka (long) eccentricity cycle was suggested. But they proved disappointing on two grounds: they did not resolve the 20,000 year precessional cycle, so apparent to the eye in the form of a basic oscillation (couplet structure) between marl and limestone. And they proved time-consuming, having yielded a geochronology for only 1.5 -1 .6 Ma of Albian time: more efficient ways to extract and process cyclic data from sediment would have to be found in order to make such studies attractive. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5 In this work I use newer methods, such as enhanced digitization of photographs and newly developed time-series analysis software tools, to extend the extraction and analyses of the cyclic patterns to the entire Albian. This approach applied to pictures of the core allowed the creation of a digitized and image-processed photographic log which has provided detailed insights on the rhythmic sedimentation history of the Scisti a Fucoidi. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6 2. CYCLOSTRATIGRAPHY 2.1 The orbital theory of ice ages Geological interest in Earth's orbital variations started with the discovery of the Pleistocene ice ages, as described in Imbrie and Imbrie (1979). In 1837 Louis Agassiz first announced his interpretation of the drift that covered much of northern Europe as a relict of a great ice sheet; a few years later Adhemar (1842) offered a theory that tried to explain Earth's precessional cycle and its effects on insolation patterns but it was only with the work of Croll (1875) that the basic principles of orbital forcing were discovered. Croll supposed that ice caps would expand beyond present limits in response to cold winters, i.e. at high eccentricity and in the perihelial summer phase of the precessional cycle. These concepts proved of great interest to the glaciologists of his time, who were just then discovering the evidence for multiple glaciations. But that interest faded when anthropological and geological evidence showed this retreat to have occurred in the last 20,000 years. In the first half of the 20t h century, the Serbian scientist Milutin Milankovitch picked up the research where Croll had left off. He first calculated the seasonal fluctuations in insolation at different latitudes and then worked on the effects of orbital variations and how they would apply to ice ages (Milankovitch, 1941); his ideas were strongly rejected at that time (see Flint and Rubin, 1955), and it was only with the works of Emiliani (1955; 1966) and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 later of Hays et al. (1976), which documented evidence in marine sequences for orbital variations pacing of climate, that Milankovitch's hypothesis gained widespread acceptance. 2.2 Orbital rhythmicity in strata The recognition of astronomically related cyclicity in sediments has a history somewhat independent of Milankovitch's theory for the ice ages. De Geer (1885) was the first to use the term "geochronology", recognizing orbital signatures within sedimentary sequences by describing the annual cycle in varves from Swedish glacial lakes, and thus becoming the first cyclostratigrapher. Gilbert (1895) observed rhythmic sedimentary alterations which he interpreted as being related to precessional forcing, in the light of Croll's book of 20 years before, and which he viewed as providing a measure of geological time. Gilbert’s paper was too visionary to elicit a rapid rush of stratigraphers into studies of cyclicity. It was 34 years before Bradley (1929) took up the challenge, to study such cyclicity in more detail, in the Eocene lacustrine-playa complexes of the Green River Formation of the Rocky Mountains. This yielded good evidence for precessional cycles, Sunspot cycles and 30-year cyclicity. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 Ca. 20 years later Schwarzacher (1947) discovered hierarchical rhythmicity in marine carbonate platform deposits, documenting the grouping of cycles into bundles of ca. 5 each, suggestive of precessional forcing. Since then the number of cydostratigraphic studies has grown at an ever-increasing pace. Cyclic sediments of purported orbital origin have been recognized in many facies and ages, though various examples have remained embroiled in controversy. The boots-and-hammer approach of the early workers, directed primarily at cyclicities visible in the field, has become supplemented by instrumental measurements, and numerous physical, chemical and biological proxies have been found to carry an orbital imprint. Improved techniques for extracting such imprints made it possible to obtain ever larger data sets, and computers with dedicated software programs have eased their processing. But also it has become clear that dense sampling and large data sets are required if cyclostratigraphy is to become significant to geology. 2.3 Cydochronology The calculations of Berger (1978) and of Laskar (1999) have extended astronomical solutions for precession, eccentricity and obliquity back to 30 my. This provides a “ target curve" to which the geological observations can be directly linked by magnetic reversals. It enabled Hilgen (1991) to push Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 cyclochronology back through the Pliocene, achieving significant improvement over the radiometric chronology. Shackleton et al. (1999) used deep-sea drilling cores to carry the continuous records of cyclicity, expressible in years- before-present, back into the Oligocene. Other cyclostratigraphers are working on older sequences to establish detailed cyclochronologies for stretches of geological time that remain “ floating”, dependent on radiometric estimates for their “ before present" timing. 2.4 Beyond chronology Chronology is not the only promise of cyclostratigraphy. It provides evidence of how components of the depositional system, at a given site and time, responded to the orbital variations. It is thus beginning to provide insight into ancient depositional settings, and into how Earth’s responses have changed with geography, in changing atmospheres and oceans. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 3 ORBITAL VARIATIONS AND THEIR EFFECTS 3.1 Overview The insolation, or receipt of solar radiation, at any given point and season at the surface of our planet varies with the position of Earth in space, and with the orientation of Earth relative to the Sun. It appears thus necessary, in order to reconstruct past climatic changes, to obtain accurate solutions for the evolution of the Earth's orbit, and axial orientation (Laskar, 1999). Earth's motion is disturbed by the other planets of the Solar System. Le Verrier (1856) was the first to compute an approximate solution for this problem, one that was later used by Croll and by Milankovitch during their quest for the astronomical origin of the ice ages. It is important to recall that even a three-body problem's solution would not be finite, but rather always an approximation; in this case we are dealing with five bodies (Mercury, Venus, Earth, Mars and Jupiter; other planets of the Solar System being too small or too distant). Improvements to solutions were provided first by Hill (1897) and then other scientists (Brouwer and van Woerkoem, 1950; Bretagnon, 1974), and subsequently by Laskar (1984; 1985; 1986; 1988; 1999) and Laskar et al., (1993). Hinnov (2000) provides a review of the improvements obtained in these last years, for instance with the introduction of new numerical techniques, the inclusion of new high order terms, and the incorporation of lunar and relativistic effects in the computation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11 of orbital elements. The basic terms, showing the interactions with Jupiter, Saturn, Mars, Venus and Mercury, are shown in Table 1. New planetary solutions were necessary in order to explore long-term stability of the Solar System. Peterson (1993) suggested the possibility of chaotic behavior and Laskar eventually (1999) substantiated it; nonetheless, the parameters observed in the Albian, ca. 100 my ago, fall nicely into the retrojected behavior of the present system, with no apparent trace of chaos. The new solution for Earth's orbital parameters has proved to be excellent in the evaluation of the relationship between orbitally forced insolation and our planet's climatic responses, particularly in the high-resolution calibration of Late Cenozoic stratigraphy (Hinnov, 2000). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12 Table 1 Earth's orbital parameters in terms of the planetary fundamental frequencies. Earth's axial precession rate is estimated at k= 50.4712"/year, which gives a frequency of revolution of 3.8944x1 O'2 cycles/ky (i.e., a period of revolution of 25678 years). Subscript numbers identify the planet: 1 = Mercury, 2 = Venus, 3 = Earth, 4 = Mars, and 5 = Jupiter; for each of these planets, the fundamental frequencies gj indicate changes in orbital eccentricity and longitude of perihelion, and sj indicate changes in orbital inclination and longitude of the ascending node, for the ith planet (Laskar 1990). Labels P-|, P2, E, e i, e2, and O indicate major orbital components labeled in Figs. 6,7, and 8. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13 Fundamental T A B L E I A. Precession index frequency period frequency (cycles/kyr) (years) r k+g 5 4.22x10 -2 23684 L - k+g 1 4.33x10 -2 23115 k+g 2 4,47x10 -2 22373 r k+s 3 5.23x10 -2 19104 L k+g 4 5.28x10 -2 18952 Amplitude modulations o f the precession index: Fundamental frequency period frequency (cycles/kyr) (years) 84"83 4.250x10 -4 2352900 81-85 1.040x10 ' 3 961700 S2"S 1 1.435x10 -3 697000 - S1-S5 2.475x10 -3 404100 [ - 83-82 7.646x10 -3 130800 L g 4'82 8.071x10 -3 123900 JT 83-85 1.012x10 -2 98800 : L g4-g5 1.055x10 -2 94800 Fundamental C. Obliquity frequency period frequency (cycles/year) (years) — k+s 3 2.44x10 -2 40996 k+S4 2.52x10 -2 39657 k+s 6 1.86x10 -2 53714 k+s j 3.46x10 -2 28889 D. Amplitude modulations o f the obliquity: Fundamental frequency period frequency (cycles/kyr) (years) s4-s3 8.24x10 -4 1214174 s3‘s6 5.78x10 -3 173145 s4-s6 6.60x10 -3 151536 s l-s4 9.40x10 -3 106394 s l"s3 1.02x10 -2 97822 s r s6 1.60x10 -2 62507 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14 3.2 Earth's orbital parameters Earth's orbital parameters can be distinguished in primary, that is different kinds of motions of Earth during its orbit, and secondary, modifications that occur periodically in these motions 3.2.1 Primary orbital parameters a. Earth rotates around its own axis in what is a daily cycle (rotation). b. Earth orbits around the Sun in what is an annual cycle (revolution). This orbit is elliptical and the Sun occupies one of the two fod of the ellipse. c. Earth's axis is tilted at approximately 23.5° from vertical. This tilting (iobliquity) is responsible for seasons. 3.2.2 Secondary orbital parameters (Fig. 3) a. the tilt (obliquity) of Earth's axis of rotation relative to the plane (ecliptic) in which it orbits the Sun. This varies between 21.8° to 24.4° (Bradley, 1985) on a 41 ka timescale (minor components at 29 and 54 ka). b. the precession of Earth's axis of rotation (also known as lunisolar precession). The rotational axis gyrates, changing the season at which Earth is closest to the Sun, and has a period of ca. 27 ka relative to the galaxy. Relative to the axis of the orbit (perihelion) periodicity is multimodal and vary between 14 and 28 ka. Precession is intimately intertwined with eccentricity in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15 ECCENTRICITY OBLIQUITY PRECESSION INDEX ; ■ I " ■ ■■ l— i | l l I I 0 200 400 600 800 TIME (KILOYEARS AGO) Fig. 3 Cycle patterns of the orbital variations. The eccentricity pattern shows the interaction of the ca. 100 and ca. 400 ky cycles. The obliquity cycle remains farly steady but has slowed down through geological time, along with the Earth's spin. The precession index expresses the modulation of the precessional cycle by the orbital eccentricity and depicts the deviation of seasonality from an average state which would be a horizontal mid-line. In this cycle, the northern and southern hemispheres are 180° out of phase. Based on Fischer and Bottjer, 1991, from Imbrie and Imbrie, 1979. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16 controlling insolation (precession-eccentridty syndrome). The combined effects of precession of the elliptical orbit and the axis of rotation are to produce a period of 23 ka. Similarly, the cyclic changes in eccentricity and the special effects exerted by our neighbor, Mars, produce another mode at 19 ka. The two periods, 23 and 19 ka blend together so that perihelion coincides with seasonal summer in each hemisphere approximately every 21.7 ka. This combined effect causes the observed shifting of the equinoxes relative to the calendar. c. the ellipticity (eccentricity} of Earth's orbit, which changes the distance from Earth to the Sun during the course of a year. It has a variable period of ca. 100 ka and a fixed period at ca. 400 ka. Eccentricity values range between almost 0 (almost circular orbit) and 0.06 (maximum ellipticity), and Earth - Sun distance may vary from ca. 147 to ca. 152 million km, at the perihelion and aphelion during maximum eccentricity respectively. 3.2.2.1 Obliquity Perturbations in obliquity tend to amplify the seasonal cycle in the high latitudes of both hemispheres simultaneously, expanding and shrinking the areas within polar and tropic circles. The greater the tilt, the more intense are the seasonal differences in both hemispheres. Obliquity plays the same role in both hemispheres during the same local season. That means that the energy Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17 received at high latitudes gets redistributed, alternately concentrating and dispersing the insolation poleward of the polar circle. This results in alternate intensification and diminishing of the meridional minimum of summer insolation associated with the polar circle (Hay et al., 1997). Therefore, with greater obliquity polar summers get hotter and winters get colder (Broecker & Denton, 1990). It is often assumed that there is no annual change in the insolation received at the obliquity frequency. This is not quite the case. The polar circles, being located at 90° minus the obliquity, expand and contract in direct proportion to it. In polar regions, an increase in summer insolation cannot be balanced by a decrease in winter insolation because the insolation is already zero in the winter (polar night). Although obliquity controls the total amount of energy received during a season, the length of the season is controlled by precession. The net annual change in insolation increases toward the poles and can reach maximum values of 17 W/m2. This value is large enough to have significant climate effects (Crowley & North, 1991). The effects of obliquity play a more important role in high latitudes than in the equatorial region but its power is always less than precession. For what has been said, the two hemispheres are in opposite phases. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18 3.2.2.2 Equinoxial precession cycle Taken together the two effects, precession of the elliptical orbit and the precession of the axis of rotation, result in the precession of the equinoxes (first recorded in 129 BC by Hipparchus). Climatic effects of the precession are entirely due to the eccentricity of the orbit, and wax and wane with the variations of eccentricity, which split the precession frequency into 19 ka and 23 ka modes. These are the periods expected in the stratigraphic record, but extreme periods between 14 and 28 ka can occur (Berger & Tricot, 1986).The equinoxes (currently March 21 and September 22) and solstices (currently June 21 and December 21) slowly shift around Earth's orbit, with a period of - 21700 years. The equinoxes are the two times in the year when the Sun is above the equator, crossing it, and day and night are of equal duration. In a circular orbit they would lie precisely half-way between the dates of perihelion and aphelion, but in an elliptical orbit they are displaced toward the time of perihelion. Every half-cycle (ca. 11 ka) the date of equinoxes oscillates in the calendar, hence the name "precession of the equinoxes". The precession of the axis of rotation is caused by the torque of the Sun, moon, and the planets on Earth's equatorial bulge which let the axis of rotation "wobble" like that of a spinning top. The net effect is that the North Pole describes a circle in space, with respect to the "fixed" stars (Beatty, 1990; Crowley & North, 1991). A significant effect is that, according to Kepler's second Law of Gravitation, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 19 planets move more slowly at aphelion than they do at perihelion. As a result, Northern summer on Earth is presently 2 to 3 days longer than southern summer, which gives the Sun more time to warm the northern continents. The precession of the equinoxes alters Earth-Sun distance at any given time of the year and therefore causes latitudinal and seasonal redistribution of solar radiation at the top of the atmosphere. The precession determines whether Earth is near or far from the Sun during summer in a given hemisphere. In other words it determines whether the seasonality resulting from tilt changes is enhanced or weakened by the seasonality due to solar distance. The daily insolation is controlled by precession at all latitudes except during polar night, when the insolation goes to zero. In one phase of rotation (present time) the southern hemisphere faces perihelion in its summer and aphelion in its winter, and the seasons are intensified; the northern hemisphere instead faces aphelion in its summer and perihelion in its winter and its seasonality is diminished. In opposite phases of the cycles, the situation is reversed. The large changes in the seasonal insolation forcing do not appear in the global annual mean, because any increase in summer insolation is balanced by an equivalent decrease in winter insolation. The effect of precession is to produce warm winters and cool summers in one hemisphere while producing cold winters and hot summers in the other hemisphere. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 0 Although the obliquity effect is more important at high latitudes than at low latitudes, the long-term variations of the daily insolation are dominated by precession, except at the high latitudes of the winter hemisphere. The average value of insolation over a season (total amount divided by its length) is mainly controlled by precession because obliquity varies only slightly around a mean value. The surface temperature response to orbital insolation variations is a function of the land-sea distribution (Short et al., 1990). Over the open ocean, precession effects are generally small because the large heat capacity of water suppresses seasonal temperature changes. The higher heat capacity of the oceans was already mentioned by Lyell (1830-1832), when he said that the ocean tempered the climate, "moderating alike an excess of heat or cold". The lower heat capacity of land causes larger changes in the seasonal cycle of temperature. During the Cretaceous the greatest area of land is in the mid latitudes, where the thermal response to processional forcing is greatest. 3.2.2.3 Eccentricity cycles and modulations of precessional effects Changes in the eccentricity determine the amplitude of the effect of the precession of the equinoxes (modulation of precession), that is, the only parameter which can change the amount of insolation received by Earth at perihelion (time when Earth is closest to the Sun) and aphelion (time when Earth is farthest away from the Sun) and the length of the seasons, through Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21 altering the mean distance from Earth to the Sun (Berger, 1977, Berger and Loutre, 1994). The total energy is maximal for the most elliptical orbit and minimal for the circular orbit. The annual difference between the two extremes (e = 0.075 and e = 0) amounts to 0.25 %. If the orbit is circular (eccentricity e = 0.00), the insolation received during the year is equal at all times. Presently, the ellipticity is 0.0167 (Earth is 5.1 million kilometers (ca. 2%) closer to the Sun at perihelion than at aphelion) and the insolation received at perihelion is approximately 352 W/m2, and at aphelion 329 W/m2, a difference of 6.68% (Floegel, 2003). At the maximum eccentricity (0.075) during the past 5 million years, given by Berger (1987), the difference in insolation between perihelion and aphelion is 30%. When eccentricity reaches 0.05 Earth receives 20% more energy at perihelion than at aphelion. The distribution of the energy received at perihelion and aphelion is modulated by the precession of the elliptical orbit and axis of rotation, so that the effects are concentrated alternately in one hemisphere and then the other. The result is an oscillation of the intensity of seasonality between the northern and southern hemispheres and shifts of the low-latitude climate zones. The caloric equator connects places at sea level with the highest MATS (Mean Annual Temperature); it is presently located in the Northern Hemisphere (NH). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 22 3.2.2.4 Long-term changes There is evidence that Earth's rotational history and Earth-Moon dynamics through time had a significant effect on Earth's precession rate and obliquity (Fig. 4) (Berger et al., 1989,1992; Berger and Loutre 1994). In particular, a slower velocity implies longer periodicities for these two parameters. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23 Obliquity » 40 c ■ o o •c 0 ) o. < * n Precession 20 100 o 400 300 200 my before present Fig. 4 Changes through time of orbital periods for obliquity (top) and precession (below); based on Berger et al., 1989 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24 4 GEOLOGICAL OVERVIEW The Sdsti a Fucoidi formation is part of the Umbria-Marche pelagic succession, in the northern Apennines of central Italy (Fig. 5). This whole succession is characterized by a thick sequence of largely pelagic limestones and marls, which record deposition on the subsiding continental margin of the Adriatic promontory, or "Adria" (Channel et al., 1979), from the time of rifting, in the Late Triassic, until the onset of thrusting and folding of the Apennines in the Miocene. This sequence provides a continuous and remarkable record of many aspects of Earth history during an interval of 170 million years (Cresta et al., 1989). During the Late Triassic and Early Jurassic, rifting took place within formerly continuous continental crust at the southern margin of Europe (i.e. Centamore et al 1971; Coltorti & Bosellini, 1980; Alvarez & Montanari, 1988). This rifting formed the oceanic basins ancestral to the present Alpine mountain chains, including the Pennine-Liguride Ocean. This new ocean outlined a northward-pointing promontory of the African continental crust, the "Adria" microplate, which was isolated from inputs of clastic sediments. As a large, and nearly isolated passive continental margin, Adria underwent extensional faulting. Normal faults defined a complex of differentially subsiding blocks. Where shallow-water carbonate deposition could keep up with subsidence, very thick sequences of shallow-water carbonates developed on Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25 AGE FORMATION SEDIMENTATION AND TECTONICS 1500- > > 0 t < £ 1000 • 500 I S -il a Schlier ScagliaRossa Scagtia Bianca Fucotd Marts M aiolica prc-flyscb a n d synorogcnic f t y s c h sedimentation pelagic and turbiditic sedimentation during reactivated tcctonism pelagic sedimentation on leveled bottom pelagic sedimentatioa oo fauk'bltick t o p o g r a p h y __ subsiding carbonate platform L-5 3 I LITHOLOGV B r * l| chcn-frec limestone U M chetty limestone lAAA I very cherty limestone massive (ncntic) limestone tiXXU nodular limestone fc " C | marly limestone and marl sandstone Fig. 5 Stratigraphic and tectonic synthesis of the Umbria-Marche sedimentary sequence, from Alvarez and Montanari, 1988. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 26 the Adriatic promontory crust, such as the prominent Lazio-Abruzzi platform; in other areas, such as that of Umbria-Marche, subsidence caused the sea floor to become deeper and deeper, to drop below the zone of shallow-water carbonate deposition. The oldest widely exposed formation within the succession is the Hettangian Calcare Massiccio, a neritic platform-carbonate unit which constitutes the core of the anticlines in the whole region. By the middle Liassic, the entire region of the Umbria-Marche area had subsided to depths where neritic carbonate deposition was no longer possible, and pelagic sedimentation began. Throughout the rest of the Jurassic, pelagic sediments show a clear facies difference between the deeper water, complete (or basinal) sequences and the shallower water, condensed and interrupted (or seamount) sequences (Fig. 5). These facies variations represent differential subsidence of fault-bounded crustal blocks inherited from the extensional tectonic phase in the Early Liassic. In basinal areas, the rest of the Jurassic is represented by the "Complete Sequence", about 300 meters thick, overlain by the about 400 meters thick Maiolica formation. The Complete Sequence (Corniola, Rosso Ammonitico, Marne a Posidonia, and Calcari Diasprigni) expresses areas of greater subsidence rate, and is characterized by thick sequences of radiolarian cherts. Frequent slumps, pebbly mudstones, megabreccias, and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 27 turbidites reflect the presence of steep slopes within the basin, which in turn shows that extensional faulting was still active (i.e. Castellarin et al., 1978; Coltorti & Bosellini, 1980; Lowrie & Alvarez, 1984; Alvarez & Montanari 1988). During the deposition of the thick, basinal Maiolica formation, which spans the interval from uppermost Jurassic to lowermost Aptian, these indications of sedimentary and tectonic instability are gradually reduced. By the mid Cretaceous differential subsidence was largely terminated and the sedimentary filling had largely leveled out the irregular topography of the paleobasin. This is evident from the deposition of the "Livello Selli", a regional, 1-m thick bituminous bed, which marks the transition to the Scisti a Fucoidi (Coccioni et al., 1987; 1989), and from the uniformity of thickness and facies of the latter pelagic sediments throughout the Umbria-Marche region. This level represents the local expression of the global oceanic anoxic event # 1 (OAE 1). In the shallower, seamount areas the Jurassic from Late Pliensbachian time onward is represented by the very thin (about 50 meters thick) "Condensed Sequence" (Colacicchi et al.. 1970; Centamore et al., 1971; Farinacci et al., 1981). The entire Condensed Sequence at Monte Nerone (western Marche) is represented by the Bugarone formation (Alvarez & Montanari, 1988), which according to Cecca et al. (1987) contains a 25 million years hiatus, from mid Bajocian through Early Kimmeridgian. Above the Bugarone formation a second major hiatus, representing all of Berriasian and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28 Valanginian time, is overlain by the thin seamount version of the Maiolica, which is similar in facies to the basinal Maiolica, but is about 100 meters thick instead of 400 meters. In the seamount areas, as in the basinal ones, the occurrence of the Aptian-Albian Fucoid Marls demonstrates the end of differentially active subsidence throughout the region. The Aptian-Albian Scisti a Fucoidi consist of a varicolored sequence of pelagic marls, marly limestones, subordinate limestones, and black shales enriched in organic matter. The eighteen units, distinguished within the Fucoid Marls on the basis of dominant colors and how they alternate, of occurrence or absence of black shales, and of carbonate content (Erba, 1986,1988), are uniformly distributed throughout the basin (Coccioni et al., 1989; Erba et al., 1989). Cyclic patterns (marl-limestone couplets and bundles) are particularly evident in the upper part of the sequence. The rather quiet sedimentation of the Aptian-Albian Fucoid Marls continued in the overlying Scaglia Bianca of latest Albian through Cenomanian age, the oldest lithostratigraphic unit composing the Scaglia Sequence. Close to its top, the Scaglia Bianca contains the "Bonarelli Level", a prominent, carbonate-free, regional marker bed, about one meter thick, equated to the second oceanic anoxic event (OAE 2) close to the Cenomanian/Turonian boundary (Schlanger & Jenkyns, 1976; Arthur & Premoli Silva, 1982). Beside the Scaglia Bianca, the Scaglia sequence (Scaglia means "scale" or "flake") is composed in stratigraphic order from Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 older to younger by the Scaglia Rossa, Scaglia Variegata, and Scaglia Cinerea. These terms only refer to the dominant color of the lithotypes, which are very homogeneous pelagic limestones, marly limestones and marls, particularly in the Scaglia Cinerea. In some intervals they may be associated with cherty layers or nodules, mainly containing recrystallized radiolarians. The Scaglia Rossa represents the time-interval from the Turanian through the Early Eocene. Shortly above the Bonarelli Level, the pelagic limestones of this unit take on a pink color, and oxidizing conditions prevailed in the basin from then on through the rest of the Scaglia Rossa time. Alvarez & Montanari (1988) recognized four members, two of which (R1) and (R4) contain red nodular cherty beds; (R2) is chert free predominantly calcareous, while (R3) consists of darker red marly limestones. The Cretaceous/Tertiary boundary falls between members (R2) and (R3) with the top of (R2) marked by a bleached bed. about 30-cm thick (Luterbacher & Premoli Silva, 1964; Montanari & Alvarez, 1987). Compared to the very quiet Scaglia Bianca deposition, the Scaglia Rossa shows an evident increase of syndepositional tectonism. Slump folding is noted in several levels within this unit (i.e. Baldanza et al. 1982; Lowrie & Alvarez, 1984; Alvarez & Montanari, 1988), and white calcarenitic turbidites, essentially made of displaced planktonic foraminifera, occur in parts of the basin (Montanari et al., 1988). The Scaglia Variegata, spanning the whole Middle Eocene and most of the Late Eocene, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30 represents a transitional unit from the red limestones with chert beds of the upper Scaglia Rossa (R4) to the gray marly limestones of the Scaglia Cinerea. It is characterized by marly limestones of red, white and gray color. Its lower boundary is marked by the last occurrence of chert. The top of the Scaglia Variegata is conventionally located above the uppermost reddish interval (Monaco et al., 1987). Finally, the Scaglia Cinerea (= gray), representing the interval from the latest Eocene through the Oligocene, consists of a thick, rather uniform, more marly sequence. Differently from the other Scaglia lithostratigraphic units, the Scaglia Cinerea contains several thin layers rich in air-blown volcanic biotites. They were found to be suitable for radiometric age- dating (Montanari et al., 1988). Very detailed studies of these biotites by Odin et al. (1988) and Deino et al. (1988), estimated the absolute age of the Eocene-Oligocene boundary as younger than 34.5 Ma. The Scaglia sequence has become a world reference section not only for pelagic biostratigraphy but also for magnetostratigraphy (Alvarez et al., 1977; Lowrie et al., 1982; Nocchi et al., 1986; Napoleone, 1988; Premoli Silva et al., 1988). Throughout most of the Umbria-Marche pelagic basin the Scaglia sequence is devoid of any extraformational reworked material except near the margins of the basin in Southern Umbria. Here the Lazio-Abruzzi carbonate platform endured up through the Eocene. In its proximity, slump-rich slope facies and coarse turbidites consisting of shallow-water debris derived from Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31 the carbonate platform are frequently interbedded within the Scaglia layers (i.e. Crescenti et al., 1969; Baldanza et al., 1982; Alvarez et al., 1985; Colacicchi & Baldanza, 1986; Monaco et al., 1987). These synsedimentary disturbances have been related to mild extensional tectonic phases (Alvarez & Montanari, 1988). In the Early Miocene, the Scaglia sequence was terminated by a characteristic unit called Bisciaro, which consists of alternating marly limestones and calcareous marls, rich in biogenic silica and pyroclastic material. The Bisciaro seems to display different thickness from place to place (from 20 m to 150 m). However, according to Coccioni et al. (1988) that difference may be more apparent than real due to the uncertainty where to locate the lower and upper boundaries. The Bisciaro grades into the Schlier, a light gray marly unit, very soon replaced by a turbiditic sequence, the Mamoso-Arenacea Formation (Fig. 5). These sediments spread first as sheets of turbiditic material across the region and became later restricted narrow turbidite fingers reaching into the small synclinal basins left between the rising anticlines (Centamore et al., 1978; Alvarez & Montanari, 1988). From the Early Miocene onward the tectonic regime drastically changed to one of compression. The Apennines structures were formed in an active fold-and-thrust belt by the motion of thrust sheets from southwest to northeast. The Umbria-Marche paleobasin was transformed into a variety of subbasins at Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 32 different scales. Loading of the crust by the advancing thrust sheets caused isostatic subsidence and formed a broad foredeep which gradually migrated toward the northeast. Smaller synclinal basins were formed on the flanks of the rising anticlines and were carried to the northeast as piggyback basins. Continuing thrust motion deformed the earlier turbidites, and the interplay of thrusting and turbidite deposition produced a complex sedimentary geometry. The modern foredeep basin roughly coincides with the Adriatic coastline. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 33 5 THE SCISTI A FUCOIDI IN THE UMBRIA-MARCHE AREA Within the pelagic Cretaceous sequence of the Umbria-Marche, the Scisti a Fucoidi (plate I) represent a shaly varicolored interlude of Aptian- Albian age. They overlie the Maiolica formation (Upper Tithonian- Lower Aptian p.p.) and are followed by the Scaglia Bianca (uppermost Albian-Lower Turonian). The Scisti a Fucoidi widely crop out in the Umbrian-Marchean Apennines with an average thickness of 80 meters. Facies and thickness are substantially uniform throughout the basin suggesting that the differential subsidence inherited from the extensional tectonic phase of Early Liassic was largely terminated by Aptian time. In fact, the irregular physiography of the basin was leveled out during Maiolica deposition. The Scisti a Fucoidi Formation mainly consists of coccolith-foraminiferal marls and marly clays, whereas limestones and marly limestones are subordinate, it is comparable to modern marly globigerinid ooze, deposited at depth estimated at ca. 2 km (Premoli Silva and Sliter, 1994). The mean accumulation rate, after compaction, was on the order of 4 Bubnoff units (mm/ky, m/My). Restriction of calcareous fossils to those initially calcitic indicates deposition below aragonite compensation depth, but above the calcite lysodine. All of the Tethyan foraminiferal and nannofossil zones are represented, and deposition is thought to have been essentially continuous (Premoli Silva Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34 and Sliter, 1994). These two lithologies alternate rhythmically throughout the Formation, showing very intense, eye-catching oscillations (Figs. 1 and 7). Ca. 130 thin Corg-rich black marls are scattered throughout the formation. A peculiarity of the formation is the abundance of bioturbations such as Chondrites, Zoophycos and Planolites. That is why the informal name of "fucoids" was used for defining this unit. On the basis of fluctuations in CaC03 content and color changes the Scisti a Fucoidi represent a spectacular example of what is coming to be known as the pelagic cycle pattern. The peculiarity of this unit attracted the interests of many geologists especially because the Scisti a Fucoidi are an outcropping analogue of deep-sea mid-Cretaceous sequences drilled in the Atlantic Ocean. The Scisti a Fucoidi succession is substantially uniform throughout the basin and only minor changes in facies and thickness are detectable. Also, slumps and hiatuses suggest some morphostructural controls. During the Aptian local tectonic activity expressed by slumpings, foraminiferal turbidites, and calcarenites were documented in several sections. In the southern part of the basin the pelagic sedimentary regime was disturbed by detrital supply eroded from the Latium-Abruzzi Platform. In this area the "Lower reddish marly member" is represented by whitish to greenish-gray sediments, suggesting a relationship between the sediment color and the detrital supply Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35 due to tectonic activity. This major disconformity is located close to the Aptian/Albian boundary, and it was related to a synchronous regional tectonic event of short duration (Erba and Premoli Silva, 1992). 5.1 Lithostratigraphy and sedimentation After detailed field analyses of color and carbonate content fluctuations along with black shale occurrence, Coccioni et al. (1987,1989) subdivided the Scisti a Fucoidi into six members. After the drilling of the Piobbico core 18 lithologic units were distinguished in the Scisti a Fucoidi (Erba 1986,1988; Tornaghi et al., 1989). This lithostratigraphy is more detailed but perfectly correlatable with the six members of Coccioni et al. (1987,1989). Still, most of our knowledge of sedimentation harks back to the observation of deBoer (1982,1983) and the study of an 8-m segment (our cycles 8-12) by Herbert and Fischer (1986) and Herbert et al. (1986), supplemented by other observations in outcrop and on the core (e.g. Tornaghi et al., 1989). The original sediment consisted mainly of coccoliths, pelagic foraminifera, a minor phase or biogenic silica partly or wholly attributable to radiolarians, and terrigenous siliciclastic matter (probably eolian dust) as recognized by deBoer (1982,1983), deBoer and Wonders (1984), Herbert and Fischer (1986) and Herbert etal. (1986). The dust supply appears to have Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36 been comparatively constant, while the supply of skeletal calcite fluctuated, in rhythmic fashion, to yield stratification. Beds are planar, bedding planes generally not sharply defined but gradational. The more calcareous beds contain, at odd intervals, cm-scale lenses of cross-bedded radiolarite, representing ripple-drifted radiolarian ooze. In these the tests have largely been calcified while the silica moved to fill the interior as chalcedony. (Fischer, pers. comm.). Excess silica in the limestones suggests that biogenic silica, generally not visibly preserved, fluctuated along with carbonate (Herbert et al., 1986). These findings, based on detailed study of parts of the sequence, appear applicable to all of it, but are in no sense complete, and these interpretations thus remain generalized. Isotopic records are strongly overprinted by pervasive calcite cement. While thus relatively simple in basic constituents, the stratigraphic sequence is dramatically differentiated in color, ranging from greenish gray to white, to black, and to red (Figs. 6, 7), in response to wide fluctuations in depositional redox conditions. 5.1.1 Drab facies Most of the sequence takes the drab form (Fig. 6). Greenish-gray beds of marlstone grade on the one hand into limestones, whitish by virtue of the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37 85% white limestone DRAB FACIES greenish\ RED FACIES , marl J \ red marl PAP 45% Bottom waters anaerobic ■<........... - aerobic ............. Diagenesis ^ anaerobic -■»* aerobic Fig. 6 Lithic phases, bioturbation, and inferred aeration states Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38 15m 20 m Fig. 7 Photolog and gray-scale log of a ca. 2 My section of core, comprising superbundles 12-16. Gray-scale scan shown as butterfly plot, from black in center to white (limestone) on margins. Numbers refer to superbundles (406-ky eccentricity cycles), numbered from top of Albian downward. The constituent bundles (95-ky cycles), lettered, a-d, are punctuated by single or groups of precessional black pulses (PAPs). Bundles b and c have become wholly confluent in cycle 13. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39 reflectance of calcite. On the other hand, the greenish marls grade into thin black marlstones colored by organic matter and iron sulfide, and representing precessional anoxic pulsations (PAPs). 5.1.1.1 Carbonate oscillations The initial calcite constituents were of two main sorts - coccoliths, and planktonicforaminifera, The purest limestones are mainly composed of coccoliths, foraminifera being suppressed in numbers and restricted to smaller, simpler forms (hedbergellids). Planktic foraminifera reach greatest abundance and diversity in the gray-green marls and black shales, or precessional anoxic pulses (PAPs) as they will be defined later in this work, where they attain the full complement of the Tethyan faunas, including the large and more highly ornamented species (Premoli Silva etal, 1989 a, 1989 b), 5.1.1.2Bioturbation Information on bioturbation is based on Erba and Premoli Silva’s (1994) observations, largely confined to cycles 8-12 (plate I), but appear applicable to the entire sequence by general observations in the field and on the core. The ichnofauna lacks the largest bioturbators such as Thalassinoides, probably because of water depth, but contains Chondrites (the “ fucoids" from which the formation derives its name), as well as Teichichnus and Zoophycos. Varied in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 the more calcareous beds, it becomes restricted to Chondrites in the more clay-rich members, and tends to dwindle to small Chondrites at the boundary with PAPs. The variation in ichnofauna thus parallels that found by Savrda and Bottjer (1994) in the Niobrara Formation in Colorado. There diversity of ichnofauna, size of burrows and diversity of shelly benthos are associated with oxygenated seafloors of the carbonate facies. They decline to Chondrites in the dysaerobic shales and are lacking in the anaerobically deposited black shales. It would appear that the limestones in the Scisti a Fucoidi were deposited on moderately well aerated bottoms, which turned dysaerobic with the deposition of the greenish marls. 5.1.1.3 Precessional anoxic pulsations (PAPs) Episodic intensification of this redox oscillation produced anoxia or near anoxia as recorded in black marls, which may occupy part or all of the marly bed. These PAPs have generally been referred to as black shales, but, lacking fissility and retaining considerable carbonate, are marlstones. Their carbonate content averages lower than that of the greenish-gray marls (Herbert and Fischer, 1986), owing to a reduced content of coccoliths (Erba, 1988,1992). The organic matter content generally lies in the 1-2% range and the intensity of pigmentation suggests presence of elemental carbon, supplemented by iron Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41 sulfides (deBoer, 1983; Herbert and Fischer, 1986). The average hydrogen content of the organic matter is generally low, and the abundance of wax- derived n-alkanes in the extractable compounds (Pratt and King 1986) suggests that soot may compose up to 50% of the organic fraction. Lack of fine laminations implies mixing on a microscopic scale, implying dysaerobic episodes when small nektonic animals may have disturbed the bottoms or when very small benthonic ones obtained temporary footholds. 5.1.1.4 Urbino anoxic event Distinct from the PAPs is the Urbino marlstone bed in cycle 27 (Plate I). In this, persistence of anaerobic conditions formed a 40-cm bed of finely laminated black marlstone. In persistence of anoxia and in its high organic and hydrogen content (Pratt and King, 1986) it resembles the Selli (OAE1a) unit of the Aptian and the Bonarelli (OAE2) unit of the Cenomanian, but unlike these it contains considerable calcite in the form of recrystallized laminae of planktic foraminifera, and is not cherty. It appears to represent an appreciable fraction of a 406-ka eccentricity cycle, an episode of prolonged anaerobic conditions. Its timing is roughly that of OAE1 b, but its identity with this remains in doubt. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 42 5.1.2 Red facies The red facies also consists of coccolith-globigerinid marls, showing a similar rhythmicity in oscillating carbonate contents and foraminifer-coccolith ratios, but its carbonate values remain below those attained in the drab facies. The redox cycle is generally lacking; these sediments were deposited in well- aerated water, in which all of the reactive iron minerals were converted to the ferric form. Furthermore, little or no reactive organic carbon was buried, so that the iron remained ferric through diagenesis. The degree of redness varies, there being a gradation from greenish gray marls through units tinged by pink and lavender such as in cycle 13 (Fig. 7; Plate I), to bright red marls and (rare) decalcified maroon mudstones. The amplitude of carbonate variation is reduced from that shown in the drab facies, and PAPs are missing except for a few in the transitional facies. The red facies is also set apart by lack of bioturbation. In the drab facies the vigor and diversity of bioturbators grew with oxygen supply. One might thus expect the red facies to show an even more diverse ichnofauna, with conspicuous large burrows, but this is not the case. No conspicuous burrows were noted in field and core (Fischer, pers. comm.), The sediments are not conspicuously laminated, suggesting that mixing occurred on a fine scale, but common presence of individual fine foraminiferal laminae with cm and sub-cm spacing implies little large-scale burrow-mixing. We conclude that Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43 macroburrowers, abundant at this depth in the flysch facies, were scarce on these bottoms, limited not by oxygen but by scarcity of food. 5.1.2.1 Condensed mudstones A variant of the red facies is represented by maroon mudstones, condensed zones of carbonate dissolution in the lower part of the succession. They lack microfossils and appear to be dissolution zones, stratigraphically condensed. The red-drab alternations seem unrelated to the pattern of orbital variations. 5.2 Biostratigraphy The fossil content of the Scisti a Fucoidi is dominated by calcareous nannofossils. Planktonicforaminifers are common, whereas benthic foraminifers are rare. Poorly preserved radiolarians are scattered throughout the unit; frequent radiolarian-rich layers occur in the lowermost and in the middle portion of the Scisti a Fucoidi. Very rare megafossils mainly include inoceramids and fish remains. Ammonites were recovered in the Albian of the S.S. Apecchiese km. 32.8 section only (Erba and Premoli Silva, 1994). Moreover, palynomorphs occur in the black shales. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44 The biostratigraphy of the Scisti a Fucoidi (Plate I, Fig. 20) is presently based on calcareous nannofossils and planktonic foraminifers. Although the preservation of both groups is moderate to poor, a high resolution biozonation was achieved (Premoli Silva, 1977; Lowrie et al., 1980; Monechi, 1981; Arthur & Premoli Silva, 1982; Coccioni et al., 1987,1989; Erba, 1988; Tornaghi et al., 1989). Planktonic foraminiferal biostratigraphy is based on the identification of 28 events, 11 zones, and 2 subzones, whereas 10 nannofossil events and 7 biozones were recognized. The integrated foraminiferal and nannofossil zonation was verified in several sections throughout the Umbrian-Marchean Basin obtaining a very detailed correlation and excellent estimate of hiatuses (Erba and Premoli Silva, 1992). Furthermore, this improved biostratigraphy allowed a more precise estimate of the accumulation rates. 5.3 Diagenesis Diagenetic modifications were observed in the Scisti a Fucoidi, sometimes overprinting the primary signals. In order to estimate the type and degree of diagenesis, semiquantitative and quantitative analyses of calcareous plankton, radiolarians, and micrite composition were carried out on selected portions of the Piobbico core (Erba, 1986,1992; Premoli Silva et al., 1989b; Tornaghi et al., 1989) and on the Poggio le Guaine - Fiume Bosso composite section (Coccioni et al., 1989). The Aptian portion of the Scisti a Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 45 Fucoidi is strongly modified by diagenesis. Preservation of both foraminifers and calcareous nannofossils is usually poor. Etching and overgrowth are dependent upon the lithologies. Nannofossil assemblages are generally characterized by a low diversity (= species richness). The nannoflora is dominated by Watznaueria barnesae, whereas foraminiferal assemblages are depauperated of small-sized forms (hedbergellids and globigerinelioids). Micrite is largely constituted by micarbs suggesting important dissolution and overgrowth during burial. A strong dissolution phase occur in the uppermost Aptian-lowermost Albian. That is suggested by the extremely low diversity and total abundance of calcareous nannofossils and planktonic foraminifers. The most resistant species dominate the assemblages and micarbs are extremely rare. It is inferred that dissolution acted at the sediment/water interface. In the Middle and Upper Albian some diagenesis occurs, inducing dissolution and overgrowth. However, the fairly high total abundance and diversity of both calcareous groups, the occurrence of moderately to high diagenetically susceptible taxa, and the limited abundance of micarbs point to minor secondary modifications not completely distorting the primary signal. 5.4 Cydostratigraphy The Scisti a Fucoidi exhibit a striking rhythmicity expressed by picturesque chromatic variations and carbonate content fluctuations. De Boer Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46 (1982,1983) was the first to study the rhythmicity recorded in the Scisti a Fucoidi, analyzing the Moria section and concluding that the lithological cyclicity could be related to the orbital frequencies. De Boer (1982) pointed out that the observed bedding rhythmicity is an expression of the processional and short eccentricity cycles. The quantitative study of rhythmicity in the Umbria-Marche pelagic facies extends to other Cretaceous units (Schwarzacher & Fischer, 1982; de Boer & Wonders, 1984; Fischer & Schwarzacher, 1984). A stratigraphic thickness of 50-60 m, representing a stage with an estimated duration of ca. 12 million years, implying a mean accumulation rate of 4-5 Bubnoff units (mm/ky, m/My). That made the ca. 8-cm bedding couplets likely candidates for the precessional cycle, and their grouping into bundles of five a likely expression of the short eccentricity cycle. Schwarzacher and Fischer (1982) and Fischer and Schwarzacher (1984) had reached similar conclusions about cyclic patterns in the underlying Barremian and overlying Cenomanian limestones. In order to thoroughly investigate the Scisti a Fucoidi rhythms, Premoli Silva, Napoleone and Fischer cut the Piobbico core at the Le Brecce farm, northwest of the village of Piobbico. Pratt and King (1986) described the composition of the organic matter. Investigations of the petrography, chemistry, biota, and magnetism were focused on the Upper Albian portion of the core (P. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47 achlyostaurion nannofossil Zone, T. praetidnensis foraminiferal subzone) where rhythms are particularly evident. Detailed studies mainly directed at an 8-m core segment (400 ka cycles 8-12, Plate I, Figs. 7 and 8) yielded calcium carbonate profiles and a gray-scale scan (Fig. 8) by densitometry of diapositives (Herbert and Fischer, 1986, Herbert et al., 1986). These yielded new insights into rhythmicity and sedimentation, and the gray-scale scan showed reflectivity to be an excellent proxy for calcium carbonate content, save for a step function from gray to black associated with black marlstone beds (the PAPs of this paper). Spectral studies by Park and Herbert (1987), Premoli Silva et al. (1989a), and Premoli Silva et al. (1989b) confirmed the assignment of cyclicities and discovered the presence of an obliquity signal. The stratigraphy of the core was described by Erba (1988) and Tornaghi et al. (1989). In the Upper Albian interval the carbonate content and the light transparency show strong evidence of rhythmic sedimentation with frequencies of 20 kyr, 100 kyr, and 400 kyr, thus believed to be related to orbital forcing (Herbert & Fischer, 1986; Fischer & Herbert, 1988; Fischer et al., 1991). In addition, the planktonic foraminiferal abundance (checked at 1- mm scale) shows frequencies dose to the eccentridty (116 kyr), the obliquity (44 kyr). and the processional (28 and 14 kyr) frequencies. In the fossil record of the Scisti a Fucoidi cored at Piobbico, cydic magnetic variations occur with Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 Fig. 8 Chemical and color variations in an 8-m Piobbico core segment, showing the long eccentricity cycles (II, III and IV), short eccentricity cycles (a, b, c, d) and, enlarged, precessional cycles (1, 2,3 ,4 ,5 ), as obtained through microdensitometry (left scan) and calcium carbonate content variation plot (right scan). From Fischer et al., 1991; modified from Fischer et al., 1990. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49 peaks in the same range (105,40, 26, and 19 kyr) (Napoleone & Ripepe, 1989). Fischer et al. (1991) and Fischer & Herbert (1988) correlated cycles 8- 12 of the Piobbico core to several sections outcropping in the Umbrian- Marchean Basin. The sequence of couplets and bundles was easily relocated in the Erma, M. Petrano, Moria, and Gorgo a Cerbara sections. Subsequently Herbert (Herbert et al., 1995) counted the 100-ka “ bundle” cycle by eye, through the core, and extended the count, in outcrops, to fill a fault-gap in the core and to complete the count to the top of the Albian. He arrived at an Albian duration of 11.9 Ma, as compared to the current radiometric estimate of 13±1.7 Ma (Gradstein etal., 1995). This count, however, remained undocumented. Fiet et al. (2001) measured a surface section of the Albian on Monte Petrano, some 13 km to the southeast of the Piobbico drill site. While some distinctive lithic and faunal markers provide a general correlation, an overall cycle-to-cyde correlation is not achieved, though in the end their assignment of 11.4 My to the Albian is only one 406-ky cycle short of the one of this work. The cycles in the pelagic Albian Scisti a Fucoidi are regarded as productivity cycles due to fluctuations in carbonate supply. The carbonate of the Scisti a Fucoidi is of biogenic origin, chiefly nannofossil-derived with contributions from foraminifers. The total amount of terrigenous input appears Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50 to be roughly constant (Herbert et al., 1986; Fischer & Herbert, 1988), while CaC03 content fluctuates markedly, thus reflecting changes in carbonate productivity. Indeed, planktonic foraminiferal and calcareous nannofossils assemblages vary consistently with this interpretation. The occurrence of high fertility Index species among calcareous nannofloras along with "tolerant" planktonic foraminifers in the carbonate-rich layers, and vice versa, supports that carbonate-rich layers result from an increase in primary productivity (Erba, 1986,1992; Premoli Silva et al., 1989; Tornaghi et al., 1989). Bedding couplets reflect Earth's precession, bundles record the short eccentricity cycles, and groups of bundles represent the long eccentricity cycles. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51 6 METHODS: THE PHOTOSCAN APPROACH 6.1 Introduction Since Steno in the 17t h century, individual strata or beds have been regarded as the ultimate bricks of the stratigraphic edifice of earth history. But in the development of that edifice stratigraphers paid little attention to the succession of individual strata. The description of rocks and biotas through thousands of meters of accumulation and their translation into histories reckoned in millions of years necessitated focus on groups of beds united by lithology (formations, members) or biotic content (subzones, zones, stages), leaving little time for such trivia as precise sequences of beds - many of which accumulated in hours or months. That changed with the discovery of facies in which stratification was regular and obviously related to rhythmic oscillations, induced by such processes as the orbital mechanics of Earth, from annual rhythms to those of the 400-ka eccentricity cycle. Cydostratigraphy, concerned with the detailed analysis of stratal sequences, has become a new frontier which has already brought refinement to Neogene chronology, and holds great potential for insights into past worlds. The conventional method of stratigraphy, by means the verbally described (and then graphically reconstructed) “measured section" with spot- collections of fossils or rock samples for laboratory analysis, is not well suited Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52 for the extraction of cyclic patterns. In the first place, the measurement and description of every stratum in a sequence is time-consuming and tedious. But also the cyclic patterns are commonly subtle. On the outcrop the investigator describes strata as encountered, not in synoptic context with the long series or preceding and succeeding ones: the decisions of what to call a stratum is a matter of judgement to be made on the spot, not readily revised, nor are repetitions of subtle compositional changes readily recognized. A good photograph of a core or a well exposed surface section does not offer insight into the mineralogy, textures, fossils etc., but it opens the sequence of strata - the stratofabric-\o synoptic comparison. If provided with the proper scales and digitized, the photographic distortions can be corrected by image processing. Image processing can also be used to eliminate distracting non-stratigraphic features, and to assemble strata from scattered patches of good exposure into a single profile. The colors values that distinguish the strata can be reproduced, and the darkness values measured rapidly and accurately by gray-scale scanning programs. Thus precise stratigraphic profiles of rock reflectivity may be readily obtained. Such profiles, drawn to the “stratigraphic scale" of centimeters or meters, express no more than the photographs do, but express it quantitatively and in a different manner. Furthermore, the set of numbers calculated by gray-scale scans lends itself to time-series analysis which shows, in power spectra, the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53 frequencies (stratigraphic spacing) at which periodicity is concentrated. Mean accumulation rates calculated from radiometric estimates may serve to link such frequencies to known astronomical periodicities, but ultimate identification rests on additional tests: do the frequencies thus tentatively identified occur at the appropriate spacing from each other? And do multi modal periodicities demonstrate the form to be expected? The Scisti a Fucoidi display the hierarchic cyclicity to be expected in dramatic fashion. In this work, I pick up where Herbert left, extending the extraction and analyses of the cyclic patterns to the entire Albian. When the Piobbico core was cut it was drilled in rocks with a dip of 23° in order to facilitate magnetic studies. The core was then split in the dip- direction by diamond saw, and cut into segments up to 25 cm long, which were then smoothed with 600-grade carborundum, etched and replicated on acetate for microscopic access to the biota, and photographed on 35-mm ektachrome diapositives. The digitization of these ca. 600 diapositives allowed for the modification of these images in any desired way. Image processing softwares provided means to clear a track through the photographs of non-stratigraphic features such as cracks, shadows, pits, stains or coarse features. A color- scan down this track then yielded a single line of pixels that records the entire stratigraphy, with diagenetic overprint but without subsequent noise. This Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 54 basic time-series can be reproduced to provide a photolog. Converted to gray scale values, this can be printed as a simple darkness profile or as a mirrored gray-scale log, and serves as a base for time-series analysis. For purposes of cycle discrimination, I printed the gray-scale profile in mirrored fashion, with black, coinciding with the PAPs, at the center. The preparation of the photolog and, subsequently, of the gray-scale scan, requires several steps, which are described in the following paragraphs: 6.2 Digitization of the photographs The digitization of the ca. 600 ektachrome diapositives was done professionally a few years ago, at the beginning of this research; it is currently possible to use office or home slide scanners that provide the same image quality. A common problem that occurs when dealing with core segments is the presence of "edge bias", or the dropoff in lighting, which readily produces pseudocyclicity in gray-scale scans (Herbert et al., 1999; Thurow and Nederbragt, 1999). This problem was not a factor in the Piobbico core images because of the shortness (ca. 20 cm) of the core segments. The images were scanned at five different resolutions, the biggest of which allowed sub-mm resolution of the stratofabric. This revealed, in parts of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55 the core, the presence of a sub-Milankovitch lamination cyclicity, which was not pursued as part of this work. 6.3 Cleaning and rectifying the image. (Adobe Photoshop®) Once the image was rendered in digital format, it was edited in Adobe Photoshop®. In the first attempts I corrected the dip in each picture by means of the skew function and removed the optical noise of cracks, shadows, pits and coarse bioturbation by replacing them with the color of adjacent matrix. These operation were again time-consuming and not always possible; in the end I resolved to simply clear a scanning path down the axis of the core to obtain an essentially noise-free profile of color values along this track for every picture. This procedure proved to be as adequate and more time-efficient, providing a color image devoid of any disturbance or glitch and ready for further analysis. 6.4 Gray-scale scan (NIH Image) For conversion of the colored profiles into their gray-scale equivalents I used the NIH Image 1.63 software, provided by the U.S. National Institute of Health as freeware on the internet (http://rsb.info.nih.gov/nih- image/index.html). To convert the color series of the individual pictures, using a standard window of 20 cm length, the page edited in Adobe Photoshop® is Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56 selected, copied, and pasted into the NIH Image window. The graph command then automatically converts color values into a graph of gray-scale values ranging from 0 (white) to 255 (black), pixel by pixel. Copying the graph values into Kaleidagraph® (any other spreadsheet like Microsoft Excel® would work) allowed the creation of a data base, where these segment-scans were corrected for dip by the factor cos 23°=0.92, to yield true stratigraphic depth values rather than the initial drilling depth. They were then concatenated into a continuous profile. 6.5 Recording the results. Pasting the gray-scale graph into Kaleidagraph® generates pixel values in the first column of the Data window. Moving them to a second column leaves the first as depth column by the “create series” function in the Functions menu. For example, given a scan segment extending from depth centimeters 300 to 310 cm, these are entered into the “ initial value” and “ final value” boxes of the Create Series panel. 200 pixels in this interval implies a “ pixel density” of 0.5 mm/pixel, a figure to be entered into the “ linear increment" box. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57 6.6 Smoothing I scanned the core at a pixel density of 0.8 mm, yielding a file of ca. 54,000 individual data points. Detail at this level - whether genuinely stratigraphic or the noise of 1-mm Chondrites burrows - produced a “ furry” graph obscuring the larger features sought, and required smoothing. The shortest cycle I sought to resolve was that of the precession, averaging 8 cm (at times as thin as 4 cm), and requiring detection of its two phases. This ultimately drove me to reduce the "pixel density" down to a pixel size corresponding to 6 mm of rock surface, a data file of ca. 7,500 points, as a compromise between resolution, clarity of plot and operational efficiency. 6.7 Logs Both the color profiles and the gray-scale profiles may now be concatenated into continuous profiles. Small gaps due to incomplete recovery render the upper 5.5 m unsuitable for detailed analysis, but from this point down the entire record is available for analysis, with the exception of a two- meters segment excised by a fault. The color profile may be printed as the Photolog (Table 1). The Gray scale profile may be printed as a single trace or may be mirrored to enhance the visual impact, for delineation of cycles Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58 6.8 Spectra and tuning Subsequent extraction of power spectra, the tuning of the time series to given frequencies etc. are standard procedures and are discussed in the next chapter, as is the geochronology obtained. The software used for spectral analysis is Analyseries, created for use on Apple Macintosh® computer by Paillard et al. (1996). Fortuning the time-series to specific frequencies I selected the cycle boundaries in the graphic profile and located them in the time series. I then expanded or shrank successive sets of the cycles simultaneously, by adjusting them to a template with an equal number of equispaced boundaries. This new, tuned graphic series is then resampled at equispaced intervals, in an approach toward the Fourier demand of sampling at equal time intervals. This new series, theoretically closer to time than the initial one, provided improved spectra. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59 7 RESULTS 7.1 Power Spectra In order to obtain a more objective view of the cyclicities I turn to the frequency domain of power spectra. I used tapered Thomson spectra, which are well-adapted for study of irregularly time-sampled series. The peak heights provided by these are not simple functions of confidence level, and the standard confidence-curves are not very meaningful (Mann and Lees, 1996), and therefore are not shown. The solitary eminence of the peaks of the obliquity and eccentricity peaks, and their consistent match to the predicted values in evolutive spectra (Fig. 12) speak for themselves, and the characteristic double mode of the short eccentricity adds a fingerprint. This is not true for the precession cycles, which though well developed in outcrop and core, are spectrally weak and not precisely aligned with predicted frequencies even in the tuned spectra, as discussed below. But, as shown by Hinnov (Grippo et al., in press), their amplitude modulations, subjected to f- tests, precisely match the periods of the eccentricity cycles (Fig. 13), proving their precessional origin. The spectrum of the entire scan (Fig. 11 A) shows groups of peaks, at certain stratigraphic spacings. Peaks concentrated at the extreme left (low frequency) have little significance (“ red noise” enhanced by the logarithmic scale). The group in the 40-60 cm bracket corresponds to the stratigraphic Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 60 bundle, identified by deBoer (1982), Herbert and Fischer (1986) and Park and Herbert (1987) with the 95-ky eccentricity cycle. The prominent peak at ca. 20 cm corresponds to no stratigraphic feature observed in field or core, but to the obliquity cycle found spectrally by Park and Herbert (1987) and Premoli Silva et al. (1989b). A scattering of peaks in the 9-14 cm region corresponds to the couplets identified by the same authors with the two precessional modes. The main periodicities in this spectrum are thus consonant with those previously found and identified as the major elements of the orbital variations, 7.1.1 Tuning The multiplicity of peaks in Fig. 11A derives mainly from variations in accumulation rate, i.e. from deviations of the stratigraphic space dimension from time. “ Tuning" involves the choice of some consistently recorded cyclicity, whose individual cycles in the data series can be stretched or condensed to the same length, in essence moving them out of the space domain into the time domain. The eccentricity values were taken to be the modern ones, as computed by Laskar for the last 19 My (1999). For obliquity and precession we use the Berger et al. (1989) estimates for 95-My BP, 38.9 ky for obliquity and 22.3 and 19.5 ky for the precessional mode Success or failure of tuning can be judged by whether tuning to any one cyclicity helps to align the others, or scatters them even more widely, and in the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 61 r i d c b f m a 24 /W^WVv J^a Aa A/s /Vu j^vu h i i n I I II I 11 ii y ill n 14 d c b I a 13 d c r ^ y c % s f ^ \ 1 1 n rJJ\ d 6 c b | a 400 ky up Fig. 9 Fine structure of selected 406-ky superbundles, tuned to same length, a-b-c-d, 95-ky cycles in ascending order. Cycles 13 and 14, transitional to red facies, show precessional signals of low amplitude but high fidelity, and confluence of central bundles. Amplitudes are high but fidelity of preservation is low in cycles 8 and 10, reflecting a strong obliquity signal. In cycle 24 the precessional signal has been largely wiped out by bioturbation. Confluence of the b and c bundle is shown in cycles 13,14 and 24. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 62 resulting alignment of peaks with the astronomic predictions. Choice of the periodicity to tune to is obviously limited to one that is consistently present, and shows well-defined cycle boundaries in the gray-scale log. It should be unimodal, for choice of a bimodal cyclicity would introduce a pseudo-bimodality into the others, particularly those of higher frequency. The precessional rhythm fails to qualify. The astronomic signal is strongly bimodal, and its preservation in the series is quite irregular (Figs. 7,9), with cycles apparently lost to bioturbation and in other cases added by double beats. The obliquity cycle is very stable in period, but is commonly lacking, and its cycle boundaries are masked by interference from the precession- eccentricity syndrome. The short eccentricity rhythm is consistently recorded in our series and is thus practical to tune to. The thus-tuned spectrum (Fig. 11B) shows considerable simplification. The peak for the long eccentricity emerges clearly, as do the two modes of the short eccentricity rhythm. The 20-cm peak is now an excellent match for the obliquity cycle. Couplet peaks remain scattered, but show a semblance of two groups corresponding to P, and P2 . Some distortion, however, has been introduced by tuning to a bimodal cyclicity. The long eccentricity rhythm is very stable at 406 ky, but its sporadic appearance precludes tuning to it directly. But it sets a frame into which the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63 short eccentricity signals can be fitted. In a complete series, every fourth (occasionally fifth) e-cycle boundary should come close to matching an E-cycle boundary, and this made it possible to extrapolate E-cycle boundaries for the entire sequence, to yield the E-cycle sequence shown in Plate I and Figure 20, numbered from the top of the Albian down. This exercise necessitated additions of four previously unrecognized 95-ka cycles, obscured by condensed sedimentation. The resulting spectrum (Fig. 11C) shows further simplification. Peaks for E, e„ e2and 0 remain aligned with predicted values. The couplet peaks are much simplified from 11B, presumably because no longer doubled by tuning to the bimodal 95-ky cycle, but their fit to the precession estimates is not improved. 7.2 Precessional rhythm The “ elementary cycle" is one of ca. 8-cm couplets that record a pulsation in the rate of carbonate production, attributable to variations in the vigor of coccolithophoracean algae in the photic zone. Not only did the vigor of coccolith blooms vary, but so did the composition of the flora, with species thought to be diagnostic of high fertility (upwelling) confined to the more calcareous beds. (Erba, 1991). This cyclicity pervades both the drab and the red facies. In the drab facies it is joined by a variation in redox conditions on the sea floor. The more Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 64 calcareous beds show strong bioturbation in which Zoophycos and Planolites play a role, evidence of moderately good aeration. In the marly members the ichnofauna became restricted to Chondrites, indicating dysaerobic conditions, and at times reached anoxia in precessional anoxic pulsations (PAPs) evidenced by black coloration. In the gray-scale log the precessional couplets appear as high-frequency serrations (Figs. 7, 9; Plate I). Strength and regularity of the couplets vary, with PAPs deeply segmenting the gray-scale cun/e. Some couplets have been amalgamated by bioturbation (Fig. 9, cycle 24). In the red facies the couplets show a lower amplitude variation than in the drab, corresponding to a lesser contrast in carbonate content. In decalcified condensed maroon clays (in cycles 27, 29 and 30) the precessional couplets are wiped out. On the other hand, the transitionally red marls of cycles 13 and 14 preserve the number of precessional couplets most faithfully, owing to the smaller amount of bioturbation (Fig. 9). Occasional couplets or groups of couplets have a bifid signature, suggesting a precessional double-beat previously noted in the precessional cycles at low latitudes, where the counterphased precessional cycles of the two hemispheres interact (Park et al., 1993). As described above, the decrease in deep-water oxygenation at times became intensified to the point of anoxia, so that part or all of this marl bed Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 65 V A I'V V V v ijw a J V a iJ1* «- , ■ » " j j A M * * A J H ^ JUa a o J ^ y ^ w v v ^ /m ^ A ( \ t N i ww V V ‘ w V lfv,Y 'J W ' \ J y > d ^ 4 \ r ~ n*t\r/*KSC' V^vAhA ^Hr*', v < » v « M H « - u . g j co C M K C M C O C M in C M A ^ Y ^ ^ V ^ W - * Y v ^ J u w ^ K - ^ n . " A'Vv'' V / ' v ~v y W y ^ * v , /V v *-A , M A ■sstK/** w Y ^ V ^ v u r n ^ r a l,'A /~ 'A * J v v v _ f^ / w w v " v * ^ — V " O £ § I * | s * ! “ s 0 ) o & © » §• . * -S 8 0) C O ^ x: o c /> T J ‘O 0) C O S ? 5 1 Q)=> C O 0 ) ? ~ & ? JEB C O © £ C 3 © % © C O _Q f s s C O JZ C D © •o © § * & * 3 0 ) © C D O | 6 o C O C D o S 400 ky O ) O i l O i I © © O C O £ T J JZ 5 C w O C O C c la g .§< § 8 & E Q. ** < d E E £ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 66 turns black, with elevated organic content and iron sulfide. These thin precessional anoxic pulsations (PAPs) segment the stratal sequence in an eye catching manner (Plate I; Fig. 7). Their cyclic distribution (Fig. 10,14) is discussed below. Ash gray (rather than greenish-gray) beds, shown in Figure 7 and Plate I, appear to represent relicts of such PAPs. Seasonal anoxia may have produced an alternation of anoxic and aerated times that, with gentle bioturbation in the aerated intervals, yielded a mixed product. But even one or two cm thick black marls were threatened by subsequent bioturbation, as shown in outcrop, where, in the Monte Petrano section, a PAP was laterally terminated by dense Chondrites burrowing from above (Fischer, pers. obs.). Either process could readily have left enough carbon particles in the resulting sediment to give it a distinctive ash-gray color. We speak of such beds as inferred PAPs. The tuned spectrum (Fig. 11C) does indeed show a group of peaks in the estimated spectral band, but these are scattered as compared to the peaks for eccentricity and obliquity. When examined in smaller time-slices (Fig. 12) about half of the spectra show two well-defined peaks, in some characteristically paired into the two modes, but slightly displaced toward higher and lower frequencies. The tuning did not, of course, correct for distortions by accumulation rate variations at frequencies beyond the 406 ky level. Existence of such uncorrected variations is demonstrated in Figure 9. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67 i 10.3 cm 53.4 cm 20.5 cm 12.2 cm I I I I I I 0.01 0.02 0.03 0.04 0.05 0.06 Fig. 11 Power spectra of full time-series. (A) untuned spectrum, referred to stratigraphic space. (B) spectrum tuned to 95-ky bundle. (C) spectrum tuned to 406-ky superbundle or its equivalent. E, predicted 406-ky (long) eccentricity rhythm. e1 and e2, predicted modes of the short (ca. 95-ky) eccentricity rhythm. O, predicted obliquity rhythm. P1 and P2 predicted modes of the ca. 20-ky precessional rhythm. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68 e O P| P 2 jJl 10 to 12 1 1 to 13 15 to 17 m 1 1 " ^ 16 to 18 17 to 19 Fig. 12 Spectra of 1,200 ky segments (three 406-ky cycle equivalents) as revognized by 406-ky tuning, overlapped. Note the great rise of obliquity power on upper part of core, and the red and blue shifts in the precessional modes. e. modes of short (ca. 95-ky) eccentricity rhythm O, P . astronomically predicted modes of obliquity and precessional rhythms Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69 Here individual 95*ky eccentricity bundles show time-distortions of a factor of two, much larger than the actual variation in their period. Variations below the 95-ky level could only add to this distorting factor. It nevertheless seemed desirable to test the assignment of the bundles to precessional forcing, in another way. 7.2.1 Precession confirmed The 10 My length of the Piobbico series provides an opportunity to investigate the orbital modulations during the Mid-Cretaceous. Below we assess the evidence as follows (procedures after Hinnov et al., 2002). (1) isolation of the individually recorded orbital parameters by bandpass filtering; (2) estimation of amplitude modulations of the filtered series using quadrature signal analysis; and (3) spectral analysis of the amplitude modulations and comparison with those of the predicted orbital parameters. To establish presence of precessional forcing in the Piobbico series, we filtered the precession band of the tuned series and looked for amplitude modulations matching Earth's orbital eccentricity (following Shackleton et al., 1999; Hinnov, 2000; Preto ef at, in press). Since the eccentricity is intact in the tuned series, the amplitude modulations of any existing precession signal should also be intact, despite rate-induced time misalignments in the underlying precession cycles. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70 To capture as many of the rate-induced excursions in the recorded precession cycles as possible, Linda Hinnov filtered the tuned series with a fairly broad passband, then performed quadrature analysis to recover the amplitude modulation (AM) series. The filtered series is shown in Figure 13A. Remarkably, the spectrum of the AM series (Fig. 13B) reveals the dear presence of E, and doublets e i and e i at frequencies comparable to those observed in the eccentricity band of the tuned series (cf. Fig. 13D). As with the short eccentricity of the tuned series, the AM components interpreted as ei and e2 are centered on frequencies that are slightly red-shifted relative to those of theoretical eccentricity (compare Figs. 13B, D, Table 1B). They match a measured similar shift in the eccentricity periods (Fig. 15). In sum, these results confirm that precession forcing played a decisive role in the cydic sedimentation of the Piobbico series, as has long been hypothesized. Most of the precession power (Fig. 13A) is concentrated in the PAPs- rich intervals (cycles 8-12 in Fig. 7 and Plate I). This irregular spacing of amplitude anomalies may preclude detection of the long-period eccentricity patterns sought for. This may explain why the AM series fails to mimic 0 eccentricity periodicities longer than 10 years (compare black curves, Fig. 13A, C). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. wner. Further reproduction prohibited without permission. 0 0.005 0.010 0.015 0.02 cydes&y 0 0.005 0.010 0.015 0.02 cydes/ky My before present Fig. 13 0 2 4 6 8 1 0 Amplitude modulations of precession index. (A) precession components of the 406-ka tuned gray-scale scan (gray curve), from top of cycle 8 down, obtained by Taner bandpass filtering with a lower cutoff frequency of 0.035 cycles/ky, and upper cutoff frequency of 0.060 cycles/ky, with a cutoff slope of 10A 15 db/octave. The amplitude modulations were obtained by Hilbert transformation (black curve). (B) amplitude spectrum of the amplitude modulation series shown in (A). (C) theoretical precession index over the past 10 million years (gray curve), and eccentricity series (black curve); (D) amplitude spectrum of the eccentricity series shown in (C). Labels indicate periodicity in ka. 72 7.3 Short eccentricity rhythm The couplets are grouped into sets (“bundles” ) of ca. 5. These bundles, 40 -5 0 cm thick, conspicuous in outcrop as well as in our logs, are defined by two features. The central couplets in such a bundle are generally more calcareous and more bioturbated, and therefore less sharply differentiated than are those at the boundaries. Also, in the drab facies they are punctuated by PAPs and inferred PAPs, as shown in Figure 7 and 14. A statistical distribution of PAPs and gray bands (inferred PAPs) (Fig. 14C, D) in a 10-My series, is plotted for the 20 precessions of the 406-ky eccentricity cycle. It shows their preferred incidence at bundle boundaries and peak incidence at superbundle boundaries. This distribution of PAPs would seem to be largely a primary feature, but the greater proportion of inferred ones in the mid-bundle precessions suggests that the pattern has become somewhat enhanced by the stronger bioturbation in the better-aerated conditions of the mid-bundle region. The scattering of peaks in the short eccentricity band of the raw spectrum (Fig. 11 A) is logically attributable to “ stratigraphic distortion” by varied accumulation rates. That they should be pulled together into a single one by tuning is to be expected, but the period of that peak is a very good match to the predicted one (Fig. 11B, C). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 peak eccentricity peak eccentricity peak eccentricity B PAPs inferred from C-stain ■ good PAPs 1 2 3 4 5 6 7 precessional couplets 14 15 16 17 1 6 19 20 1 2 3 A B | C D A 95 - ky bundles U ------------------------------- 406 - ky superbundle ■ » (N = 26) = 10.4 M Y Fig. 14 PAPs and the phasing of cycles. (A), gray-scale curve mirrored on black, yielding an image of carbonate cycles bounded by precessional black pulses (PAPs). (B), the alternative, mirrored on white, yielding an image of cycles centered on PAPs. (C), statistical distribution of PAPs and grayed (PBP-inferred) couplets (precessions) in a stack of 26 406-ky supercycles. Incidence of PAPs in the first precession of each 95-ky cycle would be near 100% but for their absence in the red facies and for a reduction of peaks by a running 3-point average. (D), patterns of statistical PBP incidence, projected to 800 ky, and suggested phase match to eccentricity cycles Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 74 7.3.1 Red shift In the spectra tuned to the 406-ky cycle the e i and e2 eccentricity modes, presently at 94.8 and 123.9 ky (Laskar, 1999, Table 6), appear significantly "red-shifted" toward lower frequencies (Fig. 15). An overlay of the spectra for the stacked quarter-series, the stacked half-series, and the full series (Fig. 15E) demonstrates the gain in resolution obtained from the longer series, shows this red-shift in all, and establishes the ei and e2 modes at 132.9 and 100.2 ky. Despite the shift, the difference tone E has remained essentially invariant at 407.2 ky (Fig. 15E), indistinguishable from the present value of 406 ky. On the other hand, the 406-ky cycle is only spottily dear in the time-series, and strong only in the spectrum of the second quarter, where it also appears to be slightly displaced toward lower frequencies. The explanation for the red-shift in e i and e2 lies in tuning errors. Hinnov demonstrated this as follows. In Figure 16A, the "true eccentridty series" (top curve) contains the 406-ka component (middle curve) that we seek to use as a uniform "metronome. Through identification of successive 406-ky minima. In tuning the Piobbico series, we identified the 406-ky component primarily through visual identification of bundle boundaries (Figs. 7 ,9 and 10). However, as shown in Figure 16A (arrows), the minima of the "true" eccentricity series do not occur at predse 406-ky intervals due to interference Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75 A B C D 0.01S 0 .0 0 5 0. 01 0 I I ei e2 132.9-f-407.2— 100.2 1 129.3 100.4 0.006 0.007 0.008 0.009 0.01 0.011 Fig. 15 Red shift in frequency modes of short eccentricity cycles (e1, e2) tuned to 406-ky cycle. E, the 406-ky cycle of eccentricity, is not well resolved in such short series. (A-D) power spectra for the four ''quarters” of the 10 My core series, tuned to the 406-ky cycle, (cycles 0-13.14-19.21-26.27-31). (Ea) the sum of the above spectra; (E), comparison of (a) the sum of the four quarter series; (b), the sum of the two half-series spectra; (c), the spectrum for the full series. The frequency modes of the short eccentricity (e) rhythm have been displaced to 100.2 and 132.9 ky respectively, but E, their difference tone, remains close to present value of 406 ky. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. copyright owner. Further reproduction prohibited without permission. C D Fig. 16 Tru e eccentricity True' eccentricity Assumed 406 ky minima A i A 406 ky component V t True 406 ky minima 101 Distorted eccentricity i I W lA /O I III 406? eccentricity “Distorted" eccentricity - 1 o Tuned Piobbico eccentricity iii i r r i11 | i i i i i l i i i | i i i ii i n r 0.005 0.01 0.015 cycles/ky — i—i—i—|—i —i —i —i —p 1000 1500 kiloyears (A) an approximation of the "true” eccentricity, x(t)=sin(2pt/406) + 0.9*sin(2pt/131) 4 - 0.7*sin(2pt/124) + 0.6*sin(2pt/99) + 0.9*sin(2pt/95), with minima indicated every ca. 400 ky by heavy black arrows (top curve); the 406-ky component of the "true" eccentricity, i.e., sin(2_t/406) (middle curve), with minima indicated by dashed arrows; and the "true" eccentricity replotted (bottom gray curve) and compared to a "distorted" eccentricity (bottom black curve) obtained by tuning the "true" eccentricity minima to constant 406-ky increments. (B) the amplitude spectrum of a 10-million year long "true" eccentricity series (top curve), computed as in (A), of a 10-million year long "distorted" eccentricity (middle curve) computed as in (A), and of the eccentricity band of the 9.6-million year long tuned Piobbico series (bottom curve). o > 77 with the short eccentricity cycles. In fact, over a 10 million year simulation, 75% of the local minima of the "true" eccentricity series occur at intervals slightly less than 406 ky. This means that (incorrectly) treating these minima as uniform 406-ky increments, and tuning the series accordingly, will effectively "stretch" ei and e i within the assumed 406-ky increments to slightly longer periodicities (compare the bottom gray and black curves). This is confirmed in the spectra of the original "true" and mistuned "distorted" eccentricity series shown in Figure 16B (top and middle curves). The "distorted" eccentricity spectrum closely resembles the eccentricity band of the Piobbico series (Fig 15E, middle and bottom curves). Not only is power diverted into virtually the same (lower) frequencies, but additionally, the doublet structure of ei is lost, and that of e2 is broader and less distinct This nearly identical fine-scale structure in e i and e2 of the Piobbico series and the experimentally distorted eccentricity spectra suggest that the red shift is due to a small systematic error in picking cycle boundaries. Finally, the absence of a sharp 406 ky spectral peak in the tuned Piobbico series suggests that the minima selected in the tuning deviated significantly from those of the true E component in the series. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 78 7.4 Long eccentricity rhythm At intervals the bundles of the gray-scale log are clearly grouped into sets of four, the 406-ky long eccentricity cycle (cycles 10,13,16, 24 and 30 in Figs. 7 and 10, and in Plate I). These superbundles are a larger version of the bundles. They show a similar punctuation by PAPs, a similar confluence of central bundles, and a tendency to be separated by more marly bundles. The intervening bundles do not reveal such grouping, but, as explained above, we found it possible to project the 406-ky cycle through these intervals by assigning every fourth bundle boundary to the superbundle schedule. Three superbundles (7; 27 with the Urbino black marlstone; and 30 with a thick decalcified maroon day) contain condensed intervals that require 100-ky additions to meet the next superbundle in phase. 7.5 Longer periodicities Although the Piobbico series is theoretically long enough to resolve the very long period AM components at 2.35 My, 967 ky, and 697 ky (Table 1B. Fig. 17D), neither the eccentricity band (Fig. 11) nor the AM series of the filtered precession (Fig. 13B) show evidence for these periodidties, although the latter indicates a spectral peak at 1.5 Ma. An alternative way to search for these AM components is through quadrature analysis of the short eccentricity (Table 1B): e i and e2 are in reality Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79 4 6 My downcore ■ § „ 2 60 |- 4 0 20 0 . « » ■ i .......... r ■ ■ ■ I M B ■ . . *. i . VWj . . 1 . . . . . . . 1.5 «10 2 T5. £ 0 .5 x10 v-2 ! 1 D | 1 1 1 . ■ • » - 1 • • • 0.002 0.004 0.006 0.008 0.01 0 0.002 0.004 0.006 0.008 0.01 cyeles/ky cycles/ky 4 6 My before present Fig. 17 Amplitude modulations of eccentricity. (A) short eccentricity components (gray curve) of the 406-ky tuned gray-scale scan, from top of cycle 8 down, obtained by Taner-bandpassing with a lower cutoff frequency of 0.007 cycles/ky and an upper cutoff frequency 0.0112 cycles/ky, with roll-off slope of 10A15 db/octave. Also shown is the amplitude modulation series (black curve), obtained by Hilbert transformation. (B), amplitude spectrum of the amplitude modulation series shown in (A). (C) theoretical short eccentricity components (gray curve)obtained by the same Taner bandpass applied in A, and the amplitude modulation series (black curve), obtained by Hilbert transformation. (0) amplitude spectrum of the amplitude modulation series in (C). Labels indicate periodicities in k y . Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80 doublets, each of which through time undergoes a 2.35 My long amplitude modulation; the four components comprising ei and e2 together also interact to produce a shorter 406 ky modulation. The filtered short eccentricity of the tuned series is shown along with its AM series in Figure 17A; their filtered theoretical equivalents in Figure 12C. The AM spectrum of the data (Fig. 17B) reveals major modulation periodicities in the 400 to 580 ky range. Of these, the peak at 400 ky is very sharply defined; while another, broader periodic component occurs at 1.5 My. The peaks at 500-580 ky may reflect tuning errors, i.e., errors in the choice of some of the 406-ky segments that caused one or more (true) 406 ky amplitude modulations to be mistakenly distributed over more than one 406-ka (tuned) period at a time. Most noteworthy is the absence of the predicted major 2.35 My amplitude modulation (Fig. 17D). This modulation is caused by the interaction between the moving orbital perihelia and eccentricities of Earth and Mars, g4- g3, and has been observed in the short eccentricity in Oligocene-Miocene sediment (Zachos etal. 2001). Here, however, the Piobbico series shows, instead, a modulation at 1.5 My; this is also present in the AM series of the filtered precession index band (Fig. 13B), presumably the direct stratigraphic expression of the same component. Whether this 1.5 My component is the result of geological distortion to what was originally a 2.35 My modulation, i.e., disruptions by episodic PAPs, or is evidence for a real and significantly Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81 different g4-g3 during the Mid-Cretaceous will require further investigation. There has been discussion, however, that during the Late Triassic and Early Jurassic, g4-g3 may have had a ca. 1.6 to 1.7 My periodicity (Olsen and Kent 1999; Hinnov and Park 1999). This would suggest that the Piobbico 1.5 My component may be a true expression of Cretaceous g4-g3, and that a shift in 94-93 of astrodynamical significance occurred sometime between Late Mesozoic and Middle Cenozoic times. 7.6 Obliquity rhythm The obliquity rhythm comes and goes through the core, as seen in spectra (Fig. 12) and in an extraction of the obliquity signal ( the 0.018 to 0.038 ky pass-band) from the gray-scale series (Fig. 18). This inconstancy is attributable not to modulations of the obliquity cycle itself but to Earth’s response. Largely generated in the polar regions, its episodic strength in the mid-latitudes may be largely dependent upon its transmission. Like the cycles of the precession-eccentricity syndrome, those of the obliquity drove variations in carbonate production and in bottom redox conditions. Thicker and abundant PAPs and relatively pure limestones coincide with the presence of strong obliquity signals in cycles 8-12, suggesting that primary productivity was increased at these times. The changing phase Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 82 •g 20 -20 My downcore 0.3 Q > TJ 1 CL a .. 0.1 IQ- 88 0.005 0.010 0.015 0.02 0.005 0.010 0.015 0.02 0 cycles/ky cycles/ky 4 6 My before present Fig. 18 Amplitude modulations of obliquity rhythm. (A) obliquity components of the gray-scale scan (gray curve), from top of cycle 8 down, obtained by Taner filtering with a lower cutoff frequency of 0.018 cycles/ky and an upper cutoff frequency of 0.038 cycles/ky, with 10A 15 db/octave slope at the cutoffs, and the amplitude modulations (black curve) obtained by Hilbert transformation. (6) amplitude spectrum of the amplitude modulation series estimated in (A). (C) theoretical obliquity (gray curve) and its amplitude modulation series (black curve) obtained by Hilbert transformation. (D) amplitude spectrum of the theoretical amplitude modulations of the obliquity given in (C). Labels indicate periodicity in ky. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 83 relations between the precession index and the obliquity signal largely mask the visual impression of a 40 ky regularity (Fig. 9). Interactions among the varying inclinations and ascending nodes of the planetary orbits produce amplitude modulations in Earth's obliquity variation listed in Table 1D. Since orbital inclination is the most unsteady of the planetary motions, Earth's obliquity variation is not expected to have remained stable over remote geologic times (Laskar 1999). Nonetheless, Figure 11C shows that, in the tuned Piobbico series, spectral power is concentrated at the two main predicted obliquity frequencies, k+S3=0.0244 cydes/ka and k+S4=0.0252 cycles/ky (see Table 1C), suggesting that S3 and S4 may have been invariant over the past 100 My. 7.7 Phase relations How do the stratigraphic cycles - the eccentricity bundles and the precessional couplets - relate to the precession index of Berger and others? The alternatives are shown in Figure 14A, the conventional gray-scale log, and 14B, its inverse. Do PAPs, segmentations in A and spikes in B, represent the lows or the highs of the eccentricity cycles? In the precession index curve, low eccentricity implies moderate seasonality with little contrast between the perihelia! summer phase and the perihelial winter phase of the precession. This pattern finds its match in the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84 damped gray-scale variations characteristic of the middle of the bundles. As eccentricity grows, the seasons become more damped in the perihelial winter phase and more extreme in the perihelial summer phase. We take this to be expressed in the higher amplitudes of the precessional signals at bundle boundaries. Accordingly, PAPs were preferentially associated with eccentricity peaks, at the level of both the short and the long eccentricity rhythms. The statistics for their incidence are shown in Figure 14C, their inferred relationship to the eccentricity cycles in 14D. The Quaternary sapropels of the Mediterranean - also PAPs of a sort - are also associated with high eccentricity (Rossignol-Strick, 1985). Turning to the precessional cycle, we ask whether the PAPs were formed in the phase of perihelial summers or that of perihelial winters. The former, marked by hotter-than-normal summers and colder-than-normal winters, leads to high monsoonality, likely to be expressed in high productivity. The perihelial winter phase, on the other hand, reduces seasonality and monsoons, and presumably favored stable stratification. This poses the question of whether the PAPs resulted from organic hyperproduction or from exceptional preservation of organic carbon. deBoer (1982,1983) and deBoer and Wonders (1984) took carbonate productivity to be a function of primary productivity. Herbert etal. (1986) presented evidence for more organic silica in the limestones (versus PAPs and other marls), Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 85 suggesting higher primary production in the carbonate-rich phase. The microbiota offers further support: limestones denote the times when coccolithophoraceans, part of the phytoplankton, flourished and contained the species generally identified with upwelling and fertility (Erba, 1988,1992). The richest assemblages of planktonic foraminifera, associated with the marls and PAPs, would seem to have resulted from depth-tiering, suggesting a preference for clearer oligotrophic waters (Premoli Silva et al., 1989b). These observations support the deBoer model, that PAPs represent not productivity but episodes of carbon preservation, Accordingly we assign the PAPs to the perihelial winter phase of the precessional cycle, when seasonality was damped, monsoons were suppressed, hydrodynamics reduced and stratification enhanced.. This would seem to differentiate them from the Quaternary sapropels, which originated in the very different hydrodynamic setting of a blind-alley Mediterranean and are thought to represent the high productivity in the perihelial summer phase (Rossignol-Strick, 1985). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 8 PALEOCLIMATIC-PALEOCEANOGRAPHIC INTERPRETATIONS Geologists think of the greenhouse world as a warmer one in which latitudinal climatic gradients were so low as to have kept permanent ice from reaching sea level and in which ocean temperatures, now near 3°C, hovered around what is now Earth’ s average surface temperature of ca. 15°C. That is the temperature obtained for Cretaceous ocean bottoms (Douglas and Savin, 1975; papers in Barrera and Johnson, 1999; Huber, Macleod and Scott, 2000). T.C. Chamberlin (1906) reasoned that in greenhouse times the formation of dense (very cold and moderately saline) waters in the high latitudes was diminished, while that of dense (warm but very saline) waters in the paratropics was increased. This, he proposed, moved the sites of deep- water formation to low latitudes; and turned deep ocean waters warm and more saline. As argued by Hay and DeConto (1999) a global “ halothermal” circulation of this sort could not have become permanent, lest sequestration of salt in the deep ocean turn the surface brackish. Yet episodic or localized subtropical downwelling of saline waters seems likely. Figure 19, Herrle’s (2002) model of this in the Mediterranean Tethys, embodies such downwelling and the very processes that our interpretation of the Scisti a Fucoidi call for. While global changes in atmospheric and oceanic behavior set the stage for a strong response to orbital forcing, that response is likely to have been Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 19 Paleogeographic reconstruction for Albian time, showing suggested directions of monsoonal winds and of downwelling warm saline waters. From herrle (2002), with permission. H - high pressure area, L - low pressure area The star shows hypothetical location of studied sequence 88 heightened by the local geography (Fig. 19). The opening of Tethys to the west, in Jurassic-Cretaceous times, provided an avenue for East-West water transport. It seems likely that trade winds drove warm, saline, nutrient-depleted waters into the westward-narrowing funnel of Tethys, as suggested in Fig. 19, and that at times and places such waters of the mixed layer foundered to bottom. As pointed out by Herrle (2002), the still comparatively aggregated pattern of lands must have left this part of the world particularly liable to orbitally modulated monsoons, which presumably played a large part in local ocean dynamics and elicited strong biotic response. 8.1 Drab facies The drab facies represents the more prevalent condition, and records sedimentation in a stratified water column, which we visualize something like that of the North Pacific. There the oxygen content of surface waters, from 4-6 cm3 /l, drops to a minimum of <1 cm3 /l at about 1 km, and generally remains below 2 cm3 /l to depths of ca. 2 km, gradually rising to 4 -4 .5 cm3 /l on the deep bottoms (Dietrich and Ulrich, 1968). In the Albian Tethys, temperatures were higher and reaction rates shorter, while time brought orbitally modulated monsoons. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 89 We postulate that times of moderate to strong seasonality, associated with the summer perihelion phase of the precessional cycle, generated monsoons, invigorated oceanic circulation, and increased nutrient supply to the surface. This favored coccoliths in the photic zone, yet continued to supply oxygen to the deep bottoms, maintaining a diverse ichnofauna. The perihelial winter phase, with its reduced seasonality, would have decreased monsoonality and ocean dynamics. This would have brought more oligotrophic conditions to the surface waters, with the clarity that allowed planktonicforaminiferato thrive in depth-zoned communities. It reduced oxygen replenishment, bringing dysaerobic conditions to the bottoms and reducing the ichnofaunas to Chondrites. At such times anoxia may well have occurred in an oxygen minimum at lesser depths, but when magnified by high eccentricity the anoxic zone became extended to the bottom, to form the PAPs. 8.2 Red facies The persistence of the carbonate cycle in the red facies implies that the upper water regime continued as outlined above, though at somewhat lower carbonate levels (Herbert and Fischer, 1986) implying lower fertility. Deposition at depth occurred in very different, well-aerated waters. These we interpret as Chamberlin’s downwelling saline, nutrient-depleted tropical waters, that brought with them their high temperature and relatively high oxygen content. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 Supply of organic matter, relatively low to begin with, was now further reduced owing to the acceleration of decomposition in the 30°C regime, leaving the bottoms marine deserts, while oxidation of sediments would have proceeded rapidly at those temperatures, and would have persisted into early diagenesis occurring within the sediment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91 9 GEOCHRONOLOGY The Albian Stage is defined, by ammonites, as extending from the base of the schrammeni zone (in Tethys, the tardifurcata) zone to the end of the perinflata zone. In the absence of ammonites we depend on foraminiferal and nannofossil zonation. This does not present a problem at the top of the Albian, where the ammonite-defined boundary nearly coincides with the beginning of the Rotalipora brotzeni (= R . globotruncanoides) foraminiferal zone. It does provide some uncertainty for the base of the Albian, where the ammonite- defined base falls between the columnata and T. primula zones (Premoli Silva, 1977) (Fig. 20; Plate I). As noted above, our gray-scale scan allowed us to combine the short and long eccentricity records into an extrapolated count of the more stable 406- ky cycles, which also revealed the need to add a total of 400 ky to condensed zones. This count places the base of the columnata zone at 30.6 E-cycles for an Albian duration of 12.4 My, 500 ky longer than Herbert etal’ s calculation. On the other hand, the appearance of P. columnata preceded the beginning of Albian time. In an attempt to move as close to the ammonite-defined base as possible we have placed the boundary mid-way between the first appearance of P. columnata and that of T. primula (Plate I, Fig. 15), at 29.2 cycles or 11.9 My before the end of Albian time. By chance this maintains the 11.9 My figure initially suggested by Herbert etal, 1995. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 92 MY 10 12 CONTROL & § o (0 £ a S 8 > o ■ s . s 8 2 ? o (0 Q O ) outcrop w ■ s . 2 I* o £ o. o o s i ' □ > 406-KY CYCLES ----------- o 1 10 12 13 14 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 RED MARL — - TOP ALBIAN BIOSTRATIGRAPHY 406 812 1218 1624 2030 2436 2842 3248 3654 4060 4466 4872 5278 5684 6090 6496 6902 7308 7714 8120 • 8526 > 8932 ' 9338 • 9744 • 10150 ■ 10556 - 10962 - 11368 - 11774 - 12180 - 12586 - 12992 Uitilno event i ui ‘ g j p I 2 § i 8 a: BASE ALBIAN ♦ 3 .8 § < s P . buxtorfi .» 1 Q > • s ? .8 •! £ 2 3 • I o . Fig. 20 Albian cyclochronology as deduced from the Scisti a Fucoidi - Scaglia Bianca sequence in the Apennines of Umbria and Marche (Italy). Observations mainly on Piobbico core, supplemented by data from outcrop (Herbert et al., 1995). Paleontology after Premoli Silva (1977) and Erba(1986,1988,1992). Length of Albian estimated at 11.9 ± 0.5 My. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93 10 BROADER IMPLICATIONS The patterns of orbital cyclicity in the Aptian-Albian Sdsti a Fucoidi began in the Tithonian-Neocomian Maiolica Limestone (Herbert, 1992) and lasted, in somewhat degraded form, through the Cenomanian Scaglia Bianca Limestone (Schwarzacher, 1994). In those limestones, carbonate productivity was doubled, which generally doubles the thickness of the couplets and reduces the marly member to a thin interbed, which may or may not be developed as a PAP. Black radiolarian cherts suggest complications. Precessional redox pulses recorded in organic matter content, associated with fertility fluctuations in the coccolith flora, have been well documented by Herrle (2002) in the Aptian-Albian hemipelagic deposits of the Vocontian basin of southern France. Thin black shales and marls, showing remarkable similarity io the PAPs, occur throughout the Early and Middle Cretaceous of the North Atlantic (Dean and Arthur, 1999 and references therein). It thus appears that these precessional fluctuations in planktonic productivity and in bottom redox conditions, modulated by the precession-eccentridty syndrome, were widespread in Tethys. We suggest that the greenhouse state sensitized the oceans to orbital forcing. While halothermal circulation at times brought more oxygen into the lower waters of the tropics/subtropics, the lower carrying capacity of the warm Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94 waters implies a diminution in the amount of oxygen thus taken down globally, per unit volume of water. It is difficult to judge whether the mean turnover rate of the oceans was higher or lower than the present one, and how it may have varied with orbital forcing, but conceivably the greater role of salinity in circulation slowed the return of some of the deeper waters, All this would have tended to deplete the oxygen content of the mid-water -masses. The high temperatures, implying more rapid decomposition of sinking organic matter, must have intensified the oxygen minimum and at times extended it downward. Consumption of more organic matter in the water column left less for benthic life and for burial the deep-sea sediments. As pointed out by deBoer (1983), a number of observations suggest an accelerated rate of carbon burial in Early Cretaceous time. These include the episodic formation of large and persistent anoxic water masses (OAEs); the widespread formation of black shales in epeiric seas; and the extraordinary role which this time played in the generation of petroleum (Irving et al., 1974; Tissot, 1979). A corollary to carbon burial is the release of oxygen. Atmospheric oxygen levels at this time may have been higher than present ones, leading to a greater incidence of wildfires, possibly reflected in he high proportion of soot in the Scisti a Fucoidi (Pratt and King, 1986). The possible relation of wildfires to orbital forcing remains to be explored. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 95 As carbon dioxide emissions now move us toward a greenhouse state, we may wonder what lessons the Albian world holds for us. So long as we continue to have extensive ice in the polar regions we shall not come to feel the full brunt of a greenhouse such as the one that developed in Cretaceous time. Furthermore, we are living at a prolonged time of low eccentricity, in which orbital forcing remains moderate. Yet it seems inevitable that some changes in circulation will occur, and that the development of higher temperatures in the mid-water masses is bound to accelerate the decomposition of organic matter settling through the water column. This may in places drive the oxygen minimum to critically low levels that could interfere with diurnal migration of organisms which, in the Neogene icehouse, lost the means of coping with such oxygen deficits. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 11 THE GRAY-SCALE SCAN APPLIED TO SURFACE OUTCROPS 11.1 Introduction The photolog - gray-scale scan method can be extended to surface outcrops. In this case, it is very important to photograph in indirect light so as to avoid light-and-shade mottling. Scales need to be introduced. Distortions may be minimized by photographing with long-focus lenses from a distance, but can be corrected in Photoshop where necessary. Weathering may modify the gray-scale values in two ways: on the one hand it may lessen or obscure the color and darkness contrasts between strata; on the other, its differential attack on rock causes thin shaly interbeds to become recessed and shadowed, enhancing their contrast with intervening limestone beds. So far, I have applied aspects of these methods to two surface exposures, both in the pelagic Umbria-Marche sequence of Italy. All of the images have been taken by me with a reflex camera on diapositive film, and scanned individually on a Macintosh computer. 11.2 Aalenian Limestone (Bugarone Formation) In the pelagic Umbria-Marche facies of Italy, the Early to Middle Jurassic is partly represented by nodular, ammonite-bearing limestones of the Rosso Ammonitico type, though not necessarily red. These are now generally Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97 interpreted as deposits of seamounts or drowned platforms (for discussion and references, see Hallam, 1994). On Monte Nerone, within a few km of the Piobbico core site (Fig. 2), the Aalenian is represented by the beige to bluegray Bugarone Limestone. Bed-by-bed collecting of ammonites by Cecca etal., (1987) has established the boundaries of the standard ammonite zones. The smooth face of a quarry operated with great care for the recovery of ornamental stone proved ideal for gray-scale scanning. The photo-scan extends from the uppermost Toarcian through most of the Aalenian (Fig. 21), but lacks a record of the last ammonite (formosum) zone. Clearly defined beds represent the 100-ka short eccentricity cycle, and stronger shale breaks at intervals of ca. 4 beds represent a weakly expressed 400-ka cycle (Fig. 21). Traces of the obliquity cycle are visible in spectra (Fig. 22). The precessional cycles seem recorded in the layers of nodules; these are not very evident on the weathered surface but show up very clearly in spectra (Fig. 22). Obliquity and precession periods appear to be shorter than present ones, as predicted by Berger and Loutre (1989). The cycle count yields a timing of 3.6 ± 0.2 Ma, as compared to the radiometric estimate of 3.6 Ma. 11.3 Cenomanian Scaglia Bianca The Scisti a Fucoidi are succeeded conformably by the Scaglia Bianca Limestone. Higher carbonate productivity yielded a formation dominated by Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98 z < z 1 1 1 s £ 0. Q . 3 z < z L l i -I < < w -J 0 Q z U J a : O o o c t O ' U 1 Q . Q . 3 213cm 337cm 217cm 133cm (O cm 153cm 104cm 125cm 1 08 c m 139cm 78cm 57cm 82 79 IT 7 6 ~ 7 S ~ 74 7 3 (5 ~63~ ( 2 5 1 58 55 J2r "49" 10 08 04 19*18 01 Fig. 2 1 Ammonite zonation, Photo Log and Gray-Scale scan of the Bugarone Formation. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 22 Spectrum of the untuned scan of the Bugarone Formation, with the expected periodicities for the Jurassic Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 coccolith-globigerinid limestone, with about double the ca. 4-cm/ka accumulation rate of the Scisti a Fucoidi. Its shaly interbeds are partly siliceous, even cherty. Existence of Milankovitch cyclicity in this formation had been established in principle by Schwarzacher and Fischer (1982), by means of sampling bed-thicknesses at 10-cm intervals. Schwarzacher (1993,1994) then measured sections of this formation to 1-cm detail, including one in the Contessa Valley and one on Monte Petrano. A comparison of the scan (of an unmeasured section, and an uncorrected photograph) demonstrate the particular advantages of the photo-scan approach. As noted by deBoer (1982; 1984) and Schwarzacher (1994), the cyclicity in the basal part of the formation resembles that in the underlying Scisti a Fucoidi, It shows the same alternation of marl and limestone in couplets, which, in sets of 4-7, are grouped into bundles (stratification cycles) 50 - 70 cm thick, representing the short cycle of eccentricity. Upwards the increasingly calcareous nature of the formation reduces the shaly members to mere bedding planes or leads to simple successions of limestone beds in which the separation into bundles becomes obscure. In the upper parts of the formation the stratification cycles reappear, though here the partitioning of limestones is shared by marls and black cherts. Here bundles reach a thickness of 1.2 m. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101 Plots of field observations do not appear to correlate well between any of these sections. Despite this, a power spectrum shows a strong peak for the ca. 100 ka bundle, at a. wave length of ca. 93 cm. A peak at 360 cm could represent the 400-ka eccentricity cycle, and one at 42 ka would seem to record the obliquity cycle. But what has been lacking is the concrete observation of the cycle hierarchy. This we can now provide for the upper part of the section. A scan was obtained for the upper part of the formation (Fig. 23), exposed in an inaccessible cliff at Le Brecce (the Piobbico Core drill site). The photograph lacks a scale and is somewhat distorted by upward tilt of the camera. A 1 -m bed of oil shale and chert, near the top, is the Bonarelli Bed, OAE-2. A simple gray-scale scan of the digitized but not image-processed photograph shows a fundamental structure resembling that of the underlying Scisti a Fucoidi. The 100-ka stratification cycles (bundles) are plainly apparent, showing more or less plain subsidiary couplets. The bundles are grouped into three superbundles - two of four bundles and one of five. Greater carbonate productivity led to limestone predominance and more than doubled the accumulation rate. The middle superbundle is thicker than the others and contains an interesting substructure - a chert band in each bundle, which shifts its position within the bundle in the succession of four: it can only be an expression of the 40-ka obliquity cycle which, growing strong in this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102 Fig. 23 Photo Scan of the Scaglia Bianca Formation and raw Gray-Scale Scan and Spectrum of the untuned scan of the Scaglia Bianca Formation, with the expected periodicities for the Cenomanian e l e2 O P1 P2 ii • Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103 400-ka superbundle, added to the carbonate production, but also imposed its siliceous (non-carbonate) phase in the form of a chert band. A spectrum obtained by estimating thickness of the layers is visible in Fig. 23. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 12 SUMMARY AND CONCLUSIONS (1) Albian coccolith-globigerinacean marls and limestones of the Umbria-Marche belt (Italian Apennines), deposited at a depth of ca. 2 km, are remarkably cyclic in structure. Building on earlier studies we reanalyzed the Piobbico core with an image-processed photolog and a variety of time-series studies designed to follow orbital forcing through ten million years of deep- water sedimentation. (2) Of two basic facies, we attribute the drab one (white - greenish gray - black) to deposition in a stratified water column, the red one to deposition in downwelling saline (halothermal) waters. (3) Both reflect oscillations in the composition and vigor of planktonic carbonate producers, in the upper waters, These are expressed in ca. 8-cm marl-limestone couplets. Abundance and diversity of coccoliths and planktonic foraminifera are antithetic. Coccolith production, with indicators of high fertility, dominated the purer limestones. Abundance and diversity of planktonic foraminifera is greatest in the less-calcareous marls, and implies a preference for oligotrophic conditions. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 (4) In the drab facies, this record of oscillations in the upper waters received the overprint of redox oscillations on the bottom. A diverse ichnofauna in the limestones reflects aerated conditions, while restriction to Chondrites in the marly member of the couplet suggests oxygen deficiency. Episodically this dropped to anoxia, resulting in black marlstones (PAPs, precessional anoxic pulsations). (5) Such couplets are grouped into ca. 40-cm bundles punctuated by more marly couplets containing PAPs. (6) The red facies shows similar carbonate fluctuations of somewhat lower carbonate content, but lacks the redox cycle except in transitional conditions. Despite deposition in highly aerated settings it lacks extensive bioturbation, suggesting that supply of organic matter to the bottom was minimal. (7) To the eye, the Scisti a Fucoidi as seen in outcrop, core, photolog and gray-scale log, reveal cyclicity at two major levels, that of the elementary couplet oscillation, and its ca. 5:1 grouping into PAP--punctuated bundles. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106 (8) Digitized pictures, converted to a photolog stripped of non- stratigraphic information, served to construct a gray-scale series and gray scale log. This, by way of spectra tuned to the 406-ky eccentricity cycle, yielded confirmation of the precessional, obliquity, and short and long eccentricity rhythms. (9) Regarding precessional cyclicity, the elementary doublet cycle, impressive in the field, yielded only marginal spectral results. Low and scattered peaks, though in some intervals appropriately spaced for the two precessional modes, do not come to coincide precisely with the predicted values for the precession. This is due in large part to variations in accumulation rate, below the tuning level of 406 ky. The couplet record also shows extensive damage from bioturbation and, in places, dissolution. But amplitude modulation analysis of these signals, filtered out of the series, shows the precise eccentricity modulations to be expected, namely the eccentricity frequencies observed, and leaves no doubt as to the precessional origin of the couplets (10) Signals of the obliquity rhythm are strong in cycles 8-12, where they increased the incidence and thickness of PAPs. They are weaker and not consistently present in the remainder of the core. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107 (11) The short (ca, 95-ky) eccentricity cycles are recorded in the ca. 40-cm bundles of couplets. The low-amplitude gray-scale variations of the middle couplets of such a bundle suggest low eccentricity, while the high amplitudes (PAPs) that punctuate bundles would appear to represent eccentricity peaks. The bundles are thus inverted expressions of the 95-ky cycle, (12) Such bundles in turn are intermittently grouped into superbundles of four, inverted expressions of the long (406 ky) eccentricity cycles. These are differentiated in the manner of the bundles. (13) Interpreting the couplets in terms of precessional phases suggests that the summer perihelial phase brought monsoons, fertility that triggered maximal production of coccoliths but limited abundance and variety in planktonic foraminifera. In the drab facies bottoms were moderately well aerated as attested by bioturbation by a varied ichnofauna. The precessional winter-perihelial phase, of damped seasonality, brought a lessened production of coccoliths but a more abundant and varied foraminiferal fauna, suggesting oligotrophic conditions. In the drab facies bottoms became stressed by lack of oxygen as evidenced by restriction of bioturbation to Chondrites. When this phase coincided with high seasonality, extreme damping of seasonality brought Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 108 anoxia to the bottoms and resulted in deposition of black marlstones, precessional anoxic pulsations (PAPs). (14) To derive a chronology for the Albian, we turned to the gray scale log, where the 95-ky bundles provide a good but not unambiguous record of the short eccentricity rhythm. The intermittent appearance of the 406-ky cycle sets a framework. Fitting the 95-ky cycles into that frame necessitated the addition of a total of 400 ky, to three intervals of condensed accumulation. (15) Extrapolating the 406-ky cycle counts in the core to the entire stage we estimate the length of the Albian at 11.9 ± 0.5 My, short of Gradstein etal's radiometric estimate of 13.3 Ma, but within their confidence limits of 1.7 Ma. (16) The sensitivity of these sediments to orbital forcing may reflect in part the complexities of oceanic circulation in a greenhouse world, and in part the increased rate of chemical and bacterial processes at high ocean temperatures. (17) Factors contributing to orbital sensitivity may have included the location of the region, in a tropical seaway narrowing westward, thus admitting Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109 flux of oceanic waters. Proximity to large continental masses implies confrontation of such nutrient-depleted waters with nutrient-rich ones, fluctuating with weathering and runoff. Those factors as well as upwelling and mixing of water masses fluctuated with the orbitally driven variations in monsoonality, highest in the precessional summer phases at times of high eccentricity. (18) The time seems to have been one of exceptional rates of carbon burial, which implies an exceptional flux of oxygen to the atmosphere. The high proportion of soot in organic matter suggests that this may have found expression in extensive wildfires. (19) While the now impending greenhouse state is not likely to reach the strength of the Mid-Cretaceous one, it is likely to intensify the oxygen- minimum zone, and may in places come to interfere with the accustomed patterns of diurnal migration. (20) The photoscan method proved to be an effective means of exploring patterns of cyclicity in a sedimentary sequence; this is true not only in purposely prepared core segments but also in surface exposures Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110 (21) The measured periods of orbital variations are so dose to the predictions that there can be little doubt that orbital rhythms paced climate change in the Cretaceous. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 111 13 BIBLIOGRAPHY Adh6mar, J., 1842, Revolution des Mers: D6luges Periodiques, Publication priv6e, Paris. Alvarez, W., Arthur, M.A., Fischer, A.G., Lowrie, W., Napoleone, G., Premoli Silva, I., and Roggenthen, W.M., 1977. Upper Cretaceous- Paleocene magnetic stratigraphy at Gubbio, Italy. Geological Society of America Bulletin, v. 88:383-389. Alvarez, W., Colacicchi, R., and Montanari, A., 1985. Synsedimentary slides and bedding formation in Apennines pelagic limestones. Journal of Sedimentary Petrology, v. 55:720-734. Alvarez, W., and Montanari, A., 1988. The Scaglia Limestones (Late Cretaceous - Oligocene) in the Northeast Apennines carbonate sequence: stratigraphic context and geological significance. In: Premoli Silva, I., Coccioni, R., and Montanari, A. (eds.), The Eocene-Oligocene Boundary in the Marche-Umbria Basin (Italy), Intl. Subcomm. Paleog. Strat., Ancona, Spec. Publ., 1.1. Arthur, M.A., and Premoli Silva, I., 1982. Development of a widespread organic carbon-rich strata in Mediterranean Tethys. In: Schlanger, S.O., and Cita, M.B., (eds.), Nature and Origin of Cretaceous Carbon-rich Facies, Academic Press, London, pp. 7-54. Baldanza, A., Colacicchi, R., and Parisi, G., 1982. Controllo tettonico sulla deposizione dei livelli detritici della Scaglia cretacico- terziaria. Rend. Soc. Geol. It. 5:11-14. Barrera, E. and Johnson, C.C., eds., 1999, Evolution of Cretaceous Ocean-Climate Systems: The Geological Society of America, Special Paper 332,445 p. Beatty, J.K., 1990, The new solar system, Cambridge University Press, p. 105. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112 Berger, A., 1977, Support for astronomical theory of climatic change, nature, 269, p. 44-45. Berger, A., 1978, Long-term variations of daily insolations and Quaternary climatic changes: Journal of Atmospheric Sciences, vol. 35(2), p. 2362-2367. Berger, A., 1987, Long-term variations of caloric insolation resulting from the Earth's orbital elements, Quaternary research, v. 9, p. 139-167. Berger, A., 1989, Pre-Quaternary Milankovitch frequencies: Nature, v. 342, p. 133 Berger, A., and Tricot, C„ 1986, Global climatic changes and astronomical theory of paleodimates, in Cazenave, A., (ed.), Earth rotation: solved and unresolved problems, D. Rediel Publishing Company, Dordrecht, Holland, p. 111-129. Berger, A ., and Loutre, M.F., 1994, Long-term variations of the astronomical seasons, in Boutron, C., (ed.), Topics in Atmospheric and Interstellar Physics and Chemistry, Les Editions de Physique, Les Ulis, France, p. 33-61. Berger, A., Loutre, M.F. and Dehant, V., 1989, Influence of the changing lunar orbit on the astronomical frequencies of Pre-Quaternary insolation patterns: Paleoceanography, v. 4, p. 555-564. Berger, A., Loutre, M.F., and Laskar, J., 1992, Stability of the astronomical frequencies over the Earth's history for paleodimatic studies. Science, v. 255, p. 560-566. Bradley, R.S., 1985, Quaternary paleoclimatology: methods of paleodimatic reconstruction, Allen & Unwin, 472 p. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 113 Bradley, W. B., 1929, The varves and climate of the Green River epoch: U.S. Geological Survey Professional Paper 158. P. 87-110. Bretagnon, P., 1974, Termes k longue p6riodes dans le systeme solaire. Astron. Astrophys., vol. 30, p. 141-154. Broecker, W.S., and Denton, G.H., 1990, What drives glacial cycles ? Scientific American, January 1990, p. 49-56. Brouwer, D., and Van Woerkoem, A.J.J., 1950, The secular variations of the orbital elements of the principal planets. Astron. papers Am. Ephem., vol. 13 (II), p. 81-107. Castellarin, A., Colacicchi, R., and Praturion, A., 1978. Geodinamica della linea Ancona-Anzio. Mem. Soc Geol It. 19:741- 757. Cecca, S., Cresta, S., Pallini, G., and Santantonio, M., 1987. II Giurassico del Monte Nerone (Appennino marchigiano, Italia centrale); Biostratigrafia, litostratigrafia, ed evoluzione paleogeografica. Abstracts, ll° Convegno Fossili Evoluzione Ambiente, Pergola. Centamore, E., Chiocchini. M., Cipriani, N., Deiana, G., and Micarelli, A., 1978. Analisi dell’evoluzione tettonico-sedimentaria dei "bacini minori" torbiditici del Miocene Medio-Superiore nell'Appennino Umbro-Marchigiano e Laziale-Abruzzese: risultati degli studi in corso. Mem. Soc. Geol. It. 18:135-170. Centamore, E., Chiocchini, M., Deiana, G., Micarelli, A., and Pierucdni, U., 1971. Contributo alia conoscenza del Giurassico nell'Appennino umbro-marchigiano. Studi Geologici Camerti, 1:1-89. Chamberlin, T.C., 1906, On a possible reversal of deep-sea circulation and its influence on geologic climates: Journal of Geology v.14, p. 363-373. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114 Channell J.E.T., Lowrie W., & Medizza F., 1979. Middle and Early Cretaceous magnetic stratigraphy from the Cismon section. Northern Italy. Earth Plan.Sci. Lett., 42:153-166. Coccioni, R., Nesci, O., Tramontana, M., Wezel, F.C., and Moretti, E., 1987. Descrizione di un livello guida "radiolaritico- bituminoso-ittiolitico" alia base delle Marne a Fucoidi nell'Appennino umbro-marchigiano, Boll. Soc. Geol. It., 106:183-192. Coccioni, R., Guerrera, F., and Veneri, F., 1988. Segnalazione di un intervallo piroclastico ("Mega-P") di notevole spessore net Bisciaro inframiocenico di Arcevia (Appennino marchigiano). Boll. Soc. Geol. It, 107:25-32. Coccioni, R., Franchi, R., Nesci, 0., Wezel, C. F., Battistini, F., & Pallecchi, P., 1989. Stratigraphy and mineralogy of the Selli Level (Early Aptian) at the base of the Marne a Fucoidi in the Umbrian- Marchean Apennines (Italy). In: Wiedmann, J., (ed.), Cretaceous of the Western Tethys, 3rd International Symposium, Tubingen 1987, pp. 563-584 (Schweizerbart, Stuttgart). Colacicchi, R., and Baldanza, A., 1986. Carbonate turbidites in a Mesozoic pelagic basin (Scaglia Formation, Apennines). Comparison with siliciclastic depositional models. Sediment Geol., 48:81-105. Colacicchi, R., Passeri, L, and Pialli, G., 1970. Nuovi dati sul Giurese umbro-marchigiano ed ipotesi per un suo inquadramento regionale. Mem. Soc. Geol. It., 9:839-874. Coltorti, M., and Bosellini, A., 1980. Sedimentazione e tettonica nel Giurassico della dorsale marchigiana. Studi Geologici Camerti, 6: 189-316. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115 Crescenti, U., Crostella, A., Donzelli, G., and Raffi, G., 1969. Stratigrafia della serie calcarea dal Lias al Miocene nella regione Marchigiano-Abruzzese (Pane II, litostratigrafia, biostratigrafia, paleogeografia). Mem. Soc. Geol. It., 8:343-420. Cresta, S., Monechi, S., and Parisi, G., 1989, Stratigrafia del Mesozoico e Cenozoico nell'area Umbro-Marchigiana: Memorie Descrittive della Carta Geologica d’ltalia, v. XXXIX. Croll, J., 1875, Climate and Time, Appleton & Co., New York. Crowley, T.J., and North, G.R., 1991, Paleoclimatology, Oxford University Press, 339 p. Dean, W.E. and Arthur, M.A., 1999, Sensitivity of the North Atlantic Basin to cyclic climatic forcing during the Early Cretaceous: Journal of Foraminiferal Research, v. 29, p. 465-486. DeBoer, P.L., 1982. Cyclicity and storage of organic matter in Middle Cretaceous pelagic sediment, in Einsele, G., and Seilacher, A., eds., Cyclic and Event Stratification: New York, Springer Verlag, p. 456- 474. DeBoer, P.L., 1983, Aspects of Middle Cretaceous pelagic sedimentation in southern Europe: production and storage of organic matter, stable isotopes and astronomic influences: Geologica Ultraiectina, Utrecht, v. 31,112 p. DeBoer, P.L. and Wonders, A.A.H., 1984, Astronomically induced rhythmic bedding in Cretaceous pelagic sediments near Moria (Italy), in Berger, A.L., Imbrie, J., Hays, J., Kukla, G., and Saltzmann, B., eds., Milankovitch and Climate: Dordrecht, D. Reidel, p. 177-190. De Geer, G., 1885, Ref af motet den 6 februari 1885: Geologiska Foreningens FSrhandlingar, 93, Bd VII, Haft 9, p. 512-213. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 116 Deino, A.J.L., Drake, R.E., Curtis, G.H., and Montanari, A., 1988. Preliminary Laser-fusion “ “Ar/^Ar dating results from biotites of the Contessa Quarry section, Gubbio, Italy. In: Premoli Silva, I., Coccioni, R., and Montanari, A. (eds.). The Eocene-Oligocene Boundary in the Marche-Umbria Basin (Italy). Int. Subcomm. Paleog. Strat. Ancona, Spec. Publ., IV.3. Dietrich, G. and Ulrich, J., 1968, Atlas zur Ozeanographie, Bibliographisches Institut Mannheim, Germany, p. 40. Douglas, R. G. and S. M. Savin. 1975. Oxygen and carbon isotope analyses of Tertiary and Cretaceous microfossils from Shatsky Rise and other sites in the North Pacific Ocean, in Gardner, J. V., ed., Initial Reports of the Deep Sea Drilling Project: 32:509520. GPO. Washington, D.C. Emiliani, C., 1955, Pleistocene temperatures: Journal of Geology, v. 63, p. 538-578. Emiliani, C., 1966, Paleotemperature analysis of Caribbean cores P6304-6 and P6304-9 and a generalized temperature curve for the past 425,000 years: Journal of Geology. 74, p. 109-126. Erba, E., 1986,1 nannofossili calcarei nell’Aptiano-Albiano (Cretacico inferiore): Biostratigrafia, paleoceanografia e diagenesi degli Scisti a Fucoidi del pozzo Piobbico (Marche): Ph.D. Dissertation, Universita' degli Studi di Milano. Erba, E., 1988. Aptian-Albian calcareous nannofossils biostratigraphy of the Scisti a Fucoidi cored at Piobbico (central Italy): Rivista Italians di Paleontologia e Stratigrafia, v. 94, p. 249-284. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117 Erba, E., 1992, Calcareous nannofossil distribution in pelagic rhythmic sediments (Aptian-Albian Piobbico core, Central Italy): Rivista Italians di Paleontologia e Stratigrafia. v. 97, p. 455-484. Erba, E., Coccioni, R., and Premoli Silva, I., 1989, Gli Scisti a Fucoidi nell'area Umbro-Marchigiana: le sezioni della S.S. Apecchiese. In Cresta, S., Monechi, S. and Parisi, G., (eds.), Stratigrafia del Mesozoico e Cenozoico nell'area Umbro-Marchigiana, Memorie descrittive della Carta Geologica d’ltalia, v. 39, p. 146-164. Erba, E., and Premoli Silva, I., 1992, Apticore-Albicore Workshop (Perugia, Italy), Field Guide, Global Sedimentary Geology Program: Cretaceous Resources, Events and Rhythms, 17 p., 24 fig. Erba, E. and Premoli Silva, I., 1994, Orbitally driven cycles in trace-fossil distribution from the Piobbico core (Late Albian, central Italy). In deBoer, P.L., and Smith, D.G., Orbital Forcing and Cyclic Sequences: International Association of Sedimentologists, Special Publication 19, Blackwell Scientific, Oxford, p. 211-226. Farinacci, A., Mariotti, N., Nicosia, U., Pallini, G., and Schiavinotto, F., 1981. Jurassic sediments in the Umbro-Marchean Apennines: an alternative model. In: Farinacci, A., and Elmi, S., (eds.), Rosso Ammonitico Symposium, Roma 1980. Tecnosdenza, pp. 335- 398. Fiet, N., Beaudoin, B , and Parize, O., 2001, Lithostratigraphic analysis of Milankovitch cyclicity in pelagic Albian deposits of central Italy: implications for the duration of the stage and substages: Cretaceous Research , v. 22/3, p. 265-275 Fischer, A.G., and Bottjer, D.J., 1991, Orbital fordng and sedimentary sequences. Journal of Sedimentary Petrology, v. 61, p. 1063-1069. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118 Fischer, A.G., and Herbert, T.D., 1988. Stratification rhythms: Italo-american studies in the Umbrian facies. Mem. Soc. Geol. it.. 31:45-51. Fischer, A.G., and Schwarzacher, W., 1984. Cretaceous bedding rhythms under orbital control? In: Berger, A.L., et al. (eds.) "Milankovitch and Climate", Riedel Publ. Company, pp. 165-175. Fischer, A.G., deBoer, P.L., and Premoli Silva, I., 1990, Cyclostratigraphy, in Ginsburg, R.N., and Beaudoin, B., (eds.), Cretaceous Resources, Events and Rhythms, Dordrecht, Kluwer Academic Publishers, p. 139-172. Fischer, A.G., Herbert, T.D., Napoleone, G., Premoii-Silva, I., and Ripepe, M. 1991, Albian pelagic rhythms (Piobbico Core). Journal of Sedimentary Petrology, v. 61, p. 1164-1172. Flint, R.F., and Rubin, M., 1955, Radiocarbon dates of pre- Mankato events in eastern and central North America, Science, 121,, p. 649-658. Floegel, S., 2003, On the influence of precessional Milankovitch cycles on the late Cretaceous climate system: comparison of GCM- results, geochemical, and sedimentary proxies for the western interior seaway of North America, Doctoral thesis, Christian-Albrechts- University, Kiel, Germany Gilbert G. K., 1895, Sedimentary measurement of geologic time: Journal of Geology, v. 3, p. 121-127. Gradstein, F. M., Agterberg, F.P., Ogg, J.G., Hardenbol, J., Van Veen, P., Thierry, J. and Huang, Z., 1995, ATriassic, Jurassic and Cretaceous Time Scale, in Berggren, W.A., Kent, D.V.. Aubry, M.-P., eds., Geochronology, Time Scales and Global Stratigraphic Correlation: SEPM Special Publication # 54. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 119 Hallam. A., 1994, An Outline of Phanerozoic Biogeography, Oxford University Press, 246 p. Hay, W.W., DeConto, R.M., and Wold, C.N., 1997, Climate: is the past the key to the future?, Geol. Rundschau, v. 86, p. 471-491. Hay, W.W. and DeConto, R., 1999, Comparison of modern and Late Cretaceous meridional energy transport and oceanology, in Barrera, E., and Johnson, C.C., eds., 1999, Evolution of Cretaceous Ocean-Climate Systems: The Geological Society of America, Special Paper 332, p. 283-300. Hays, J.D., Imbrie, J., and Shackleton, N.J., 1976, Variations in the Earth's orbit: pacemaker of the ice ages: Science, v. 194, p. 1121- 1132. Herbert, T.D., 1992, Paleomagnetic calibration of Milankovitch cyclicity in Lower Cretaceous sediments: Earth and Planetary Science Letters v. 112, p. 15-28. Herbert, T.D. and Fischer, A.G., 1986, Milankovitch climatic origin of mid-Cretaceous black shale rhythms in central Italy: Nature, v. 321, p. 739-743. Herbert, T.D., Gee, J., and DiDonna, S., 1999, Precessional cycles in Upper Cretaceous pelagic sediment of the South Atlantic: Long-term patterns from high frequency climate variations, in Barrera, E., and Johnson, C.C., eds., Evolution of the Cretaceous ocean-climate system: Geological Society of America Special Paper 332, p. 105-220. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 120 Herbert, T.D., Premoli Silva, I., Erba, E., and Fischer, A.G., 1995, Orbital chronology of Cretaceous-Paleocene marine sediments, in Berggren, W.A., Kent, D.V., Aubrey, M-P., and Hardenbol, J., eds., Geochronology, Time Scales and Global Stratigraphic Correlation: Society of Economic Paleontologists and Mineralogists, Special Publication No. 54, p. 81-94. Herbert. T.D., Stallard, R.F., and Fischer, A.G., 1986, Anoxic events, productivity rhythms and the orbital signature in a mid- Cretaceous deep-sea sequence from Central Italy: Paleoceanography, v. 1, p. 495-506. Herrle, J.O., 2002, Paleoceanographic and paleodimatic implications on mid-Cretaceous black shale formation in the Vocontian basin and the Atlantic: evidence from calcareous nannofossil and stable isotopes: Ph. D. thesis, Institut and Museum fuer Geologie and Palaeontologie der Universitaet Tuebingen. Hilgen, F.J., 1991, Extension of the astronomically calculated (polarity) time scale to the Miocene/Pliocene boundary: Earth and Planetary Science Letters: v. 107, p. 349-368. Hill, G., 1897, On the values of eccentridties and longitudes of the perihelia of Jupiter and Saturn for distant epochs, Astronomy Journal, v. 17 (11), p. 81-87. Hinnov, L.A., Schulz, M., and Yiou, P., 2002, Interhemispheric space-time attributes of the Dansgaard-Oeschger oscillations between 0-100 ka: Quaternary Sdence Reviews, in press. Hinnov, L.A., 2000, New perspectives on orbitally forced stratigraphy: Annual Review of Earth and Planetary Sciences, v. 28, p. 419-475. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 121 Hinnov, L.A. and Park, J., 1999, Strategies for assessing Early- Middle (Pliensbachian-Aalenian) Jurassic cyclochronologies: Philosophical Transactions of the Royal Society of London, Series A, v. 357, p.1831-1859. Huber, B.T., Macleod, K.G., and Wing, S. L., eds. 2000, Warm Climates in Earth History: Cambridge University Press, 462 p. Imbrie, J., and Imbrie, K. P., 1979, Ice Ages. Solving the Mystery. Harvard University Press, New York and London, 224 pp. Irving, E., North, F.K., and Couillard, F., (1974), Oil, climate and tectonics: Canadian Journal of Earth Sciences, v. 11, p. 1-15. Laskar, J., 1984, Th6orie generate plan6taire: elements orbiteaux des plan6tes sur 1 million d'ann6es. Th6se, Observatoire de Paris, France. Laskar, J., 1985, Accurate methods in general planetary theory, Astron. Astrophys, v. 144, p. 133-146. Laskar, J., 1986, Secular terms of classic planetary theories using the results of general theory. Astron. Astrophys, vol. 157, p. 59- 70. Laskar, J., 1988, Secular evolution of the Solar System over 10 million years. Astron. Astrophys, vol. 198, p. 341-362. Laskar, J., 1999, The limits of Earth orbital calculations for geological time-scale use, in Shackleton, N.J., McCave, I.N., and Weedon, G.P., eds., Philosophical Transactions of the Royal Society of London, Series A., v. 357, p. 1735-1759. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 122 Laskar, J., Joutel, F., and Boudin, F., 1993, Orbital, precessional, and insolation quantities for the Earth from -20 Myr to + 10 Myr. Astron. Astrophys, vol. 270, p. 522-573. Le Verrier, U., 1856, Ann. Obs. Paris, vol. II. Paris: Mallet- Bachelet. Lowrie, W., and Alvarez, W., 1984. Lower Cretaceous magnetic stratigraphy in Umbrian pelagic limestones, Earth Planet. Sci. Letters. 71:315-328. Lowrie, W., Alvarez, W., Premoli Silva, I. and Monechi, S., 1980. Lower Cretaceous magnetic stratigraphy in Umbrian pelagic carbonate rocks. Geoph. Journ. Royal Astron. Society, 60:263-281. Lowrie, W., Alvarez, W., Napoleone, G., Perch-Nielsen, K., Premoli Silva, I., and Toumarkine, M., 1982. Paleogene magnetic stratigraphy in Umbrian carbonate rocks: The Contessa sections, Gubbio. Geol. Soc. Amer. Bull., 93:414-432. Luterbacher, H.P., and Premoli Silva, I., 1964. Stratigrafia del limite Cretacico-Terziario nell'Appennino centrale. Riv. Ital. Paleont. Strat. 70:67-128. Lyell, C., 1830-1832, Principles of Geology, first edition, Murray, London. Mann, M.E. and Lees, J.M., 1996, Robust estimation of background noise in signal detection in climatic time series: Climatic Change, v. 35 p. 409-455. Milankovitch, M., 1941, Kanon der Erdbestrahlung und seine Anwendung auf das Eiszeitenproblem: Akademie Royale Serbe, v. 133, 633 p. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 123 Monaco, P., Nocchi, M., and Parisi, G., 1987. Analisi stratigrafica e sedimentologica di alcune sequenze pelagiche dell'Umbria sud-orientale dall'Eocene inferiore all'Oligocene inferiore. Boll. Soc. Geol. It., 106:71-91. Monechi, S., 1981. Aptian-Cenomanian calcareous nannoplankton from some sections in the Umbrian Apennine. Riv. It. Paleont. Strat., 87:193-226. Montanari, A., and Alvarez, W., 1987. The geology of the Cretaceous-Tertiary boundary in the northeastern Apennines. 3° Jornadasde Paleontologia, Inter. Conf. Paleont. Evolution: Extinction Events, Leioa (Bilbao), Abstracts, p. 222. Montanari, A., Chan, L.S., and Alvarez, W., 1988. Synsedimentary tectonics in the Late Cretaceous-Early Tertiary pelagic basin of the Northern Apennines. In: Crevello, P., Wilson, J.L., Sarg, R., and Reed, F. (eds.). SEPM, Spec. Publ., 44. Napoleone, G., 1988. Magnetostratigraphy in the Umbrian pelagic sequence: Review of the development and its finer definition. In: Premoli Silva, I., Coccioni, R., and Montanari, A., (eds.), The Eocene-Oligocene Boundary in the Marche-Umbria Basin (Italy), Int. Subcomm. Paleog. Strat., Ancona, Spec. Publ. LI. Napoleone, G., and Ripepe, M., 1989. Cyclic geomagnetic changes in mid-Cretaceous rhythmites. Terra Nova, 1:437-442. Nocchi, M., Parisi, G., Monaco, P., Monechi, S., Madile, M., Napoleone, G., Ripepe, M., Orlando, M., Premoli Silva, I., and Bice, D.M., 1986. The Eocene-Oligocene boundary in the Umbrian pelagic sequence, Italy. In: Pomerol, C. & Premoli Silva, I. (eds.), Terminal Eocene Events, Develop. Palaeont. Strat., 9:25-40, Elsevier. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 124 Odin, G.S., Guise, P., Rex, D.C., and Keuzer, H., 1988. K-Ar and A Ar/A Ar geochronology of Late Eocene biotites from the northeastern Apennines. In: Premoli Silva, I., Coccioni, R., and Montanari, A., (eds.), The Eocene-Oligocene boundary in the Marche- Umbria Basin (Italy), Int. Subcomm. Paleog. Strat., Ancona, Spec. Publ. IV.4. Olsen, P.E. and Kent, D.V. 1999, Long-period Milankovitch cycles from the Late Triassic and Early Jurassic of eastern North America and their implications for the calibration of the Early Mesozoic timescale and the long term behavior of the planets: Philosophical Transactions of the Royal Society of London, Series A., v. 357, p. 1761- 1786. Paillard, D., Labeyrie, L, and Yiou, P., 1996, Macintosh program performs time-series analysis: Eos Transactions, American Geophysical Union, 77:379. Park, J. and Herbert, T.D., 1987, Hunting for paleodimatic periodicities in a geologic time series with an uncertain scale: Journal of Geophysical Research, v. 92, p. 14,027 -14,040. Park, J., D’Hondt, S.L., King, J.W., and Gibson, G., 1993, Late Cretaceous precessional cydes in double-time: a warm-Earth Milankovitch response: Science, v. 261, p. 1331-34. Peterson, I., 1993, Newton's clock: chaos in the solar system. New York, Freeman, p. 317. Pratt, L.M. and King, J.D., 1986, Variable marine productivity and high eolian input recorded by rhythmic black shales in mid-Cretaceous pelagic deposits from central Italy: Paleoceanography, v. 1, p. 507-522. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 125 Premoli Silva, I., 1977. Upper Cretaceous-Paleocene magnetic stratigraphy at Gubbio, Italy: ll-Biostratigraphy: Geological Society of America Bulletin, v. 88, p. 367-389. Premoli Silva, I., Orlando, M., Monechi, S., Madile, M., Napoleone, G., and Ripepe, M., 1988. Calcareous plankton biostratigraphy and magnetostratigraphy at the Eocene-Oligocene transition in the Gubbio area. In: Premoli Silva, I., Coccioni, R., and Montanari, A., (eds.), Int. Subcomm. Paleog. Strat., Ancona, Spec. Publ., 11.6. Premoli Silva, I., Erba, E., and Tornaghi, M.E., 1989a, Paleoenvironmental signals and changes in surface fertility in Mid- Cretaceous C-org-rich pelagic facies of the Fucoid Marls (central Italy): Geobios, Mem. Spec., v. 11, p. 225-236,6 fig., 3 tab., Lyon. Premoli Silva, I., Tornaghi, M.E., and Ripepe, M., 1989b, Planktonic foraminiferal distribution records productivity cycles: evidence from the Aptian-Albian Piobbico core (Central Italy): Terra Nova, v. 1, p. 443-448. Premoli Silva, I. and Sliter, W.V., 1994, Cretaceous planktonic foraminiferal biostratigraphy and evolutionary trends from the Bottaccione section, Gubbio, Italy: Palaeontographica Italica, v. 82, p. 1-89, 26 pi. Preto, N., Hinnov, L.A., Hardie, L.A., and DeZanche, V., 2001, A Middle Triassic orbital signature recorded in the shallow-marine Latemar carbonate buildup (Dolomites, Italy): Geology, v. 29, p. 1123- 1126. Rossignol-Strick, M., 1985, Mediterranean Quaternary sapropels, and immediate response of the African monsoon to variation of insolation: Paleogeography, Paleodimatology, Paleoecology, v. 49, p. 237-263. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 126 Savrda, C.E. and Bottjer, D.J., 1994, Ichnofossils and ichnofabrics in rhythmically bedded pelagic - hemi-pelagic carbonates: recognition and evaluation of benthic redox and scour cycles, in deBoer, P.L., and Smith, D.G., eds., Orbital Forcing and Cyclic Sequences, International Association of Sedimentologists: Special Publication 19, Oxford, Blackwell, p. 195-210. Schlanger, S.O., and Jenkyns, H.C., 1976. Cretaceous oceanic anoxic sediments: causes and consequences. Geologie en Mijnbouw, 55:179-184. Schwarzacher, W., 1947, uberdie Sedimentare Rhythmikdes Dachsteinkalkes von Lofer: Verhandlungen der Geologischen Bundes- Anstalt, v. H10-12, p. 175-188. Schwarzacher, W., 1953, Cyclostratigraphy and the Milankovitch Theory: Elsevier, Amsterdam, 225 p. Schwarzacher, W., 1994, Cyclostratigraphy of the Cenomanian in the Gubbio district, Italy, a field study, in deBoer, P.L., and Smith, D.G., eds., Orbital Forcing and Cyclic Sequences: International Association of Sedimentologists, Special Publication. 19, Oxford, Blackwell Scientific, p. 87-98. Schwarzacher, W. and Fischer, A.G., 1982. Limestone-shale bedding and perturbations of the earth's orbit, in Einsele, G., Seilacher, A., eds., Cyclic and event stratifications: Springer-Verlag, New York, p. 72-95. Shackleton, N.J., Crowhurst, S.J., Weedon, G.P., and Laskar, J., 1999, Astronomical calibration of Oligocene-Miocene time: Philosophical Transactions of the Royal Society of London, Series A., v. 357, p. 1907-1930. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 127 Short, D.A., Crowley, T.J., Mengel, J.G., Hyde, W.T., and North, G.R., 1990, Modeling 100,000 year power in monsoon series, EOS Transactions, American Geophysical Union, v. 71,43, p. 1367. Thurow, J. and Nederbragt, A.J., 1999, Cretaceous laminated sediments as climate archive: European Union of Geosciences 10, Abstract volume, p. 225. Strasbourg, France. Tissot, B., 1979, Effects of prolific petroleum source rocks and major coal deposits caused by sea-level changes: Nature 277, p. 463- 465. Tornaghi, M.E, Premoli Silva, I., and Ripepe, M, 1989, Lithostratigraphy and planktonic foraminiferal biostratigraphy of the Aptian-Albian “ Scisti a Fucoidi”, Piobbico core, Marche, Italy: background for cyclostratigraphy: Rivista Italiana di Paleontologia e Stratigrafia, v. 95, p. 223-264. Zachos, J.C., Shackleton, N.J., Revenaugh, J.S., Palike, H., and Flowers, B.P., 2001: Climate response to orbital forcing across the Oligocene-Miocene boundary: Science, v. 292, p. 474-478. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ALBIAN PIOBBICO CORE PHOTO LOG and GRAY-SCALE SCAN 0 m S V 'S 'V * ni M^i vw i A m m m sm ms mt m sm sm mmm im m m Reproduced with permission of the copyright owner. Further reproduction prohibited without D $ • 5 2 1 ui 5.50 c: .o a C O & s C D a : permission. P. buxtorfi 0.10 .5 2 to c . 3 > & Oi ■ Q o c i ■ 5 2 c o c a > .£ o h Z q: 6.40 .C O C O c; C D .£ .O -*3 (b C D Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. F A U L T 15 20 25 30 •Vk<(4 ( V -* * • * • ' ■* * =•* •* M l ■ fU h M tW U !u » ) * ■ tuW. Cb: « » * itlliiM ^ iii» ii» i» » ir >«iillli8ii •' • ■'‘ •.■'^^■/•i.,.,\U;T< ~r^rt''^r .y^t,:<. _u,<s x -M B S i.e * vS:'- r SSr scSSSx^^SSES •S ttta rw w » f» » ■WM S M 13 14 15 16 17 18 19 20 21 22 £ ■6 C O o: 19.50 C O c . C D ;Q C D Q Q 0 .s .o 0 5 Q. 23.70 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35 45 m M & m URBINO ■;*H i</*«T C .'trrtA ^ ’ V ^' “ 40 ssssssS^^ 23 24 25 26 27 28 29 30 31 C D ! " § c c o ‘C : " C : 33.76 ■ S C D C I q: 41.27 t BASE ALBIAN i 44.37 Plate I - Albian strata in the Piobbico core. (A) Photolog with stratigraphic depth (B) Gray-scale log, a butterfly-plot mirrored on black: widens to white with carbonate content, constricts with clay and carbon pigmentation. Upper 5 m contain many smal gaps in core recovery. Gap in cycle 19, missing pictures. Gap in cycles 21-22, section faulted out, representing ca. 2 m (C) 406-ka eccentricity cycles, numbered from top of Albian downward (D) nannofossils zones (E) foraminiferal zones and sub-zones ■ g .8- 1 a H! Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Evolutionary paleoecology and taphonomy of the earliest animals: Evidence from the Neoproterozoic and Cambrian of southwest China

PDF

Grain-size and Fourier grain-shape sorting of ooids from the Lee Stocking Island area, Exuma Cays, Bahamas

PDF

Early Jurassic reef eclipse: Paleoecology and sclerochronology of the "Lithiotis" facies bivalves

PDF

Characterization of geochemical and lithologic variations in Milankovitch cycles: Green River Formation, Wyoming

PDF

A phylogenetic analysis of oological characters: A case study of saurischian dinosaur relationships and avian evolution

PDF

Holocene sedimentation in the southern Gulf of California and its climatic implications

PDF

Helicoplacoid echinoderms: Paleoecology of Cambrian soft substrate immobile suspension feeders

PDF

Barnacles as mudstickers? The paleobiology, paleoecology, and stratigraphic significance of Tamiosoma gregaria in the Pancho Rico Formation, Salinas Valley, California

PDF

Preservation Of Fossil Fish In The Miocene Monterey Formation Of Southern California

PDF

Fourier grain-shape analysis of quartz sand from the Santa Monica Bay Littoral Cell, Southern California

PDF

Lateral variability in predation and taphonomic characteristics of turritelline gastropod assemblages from Middle Eocene - Lower Oligocene strata of the Gulf Coastal Plain, United States

PDF

Investigation into the tectonic significance of the along strike variations of the Peninsular Ranges batholith, southern and Baja California

PDF

Integrated geochemical and hydrodynamic modeling of San Diego Bay, California

PDF

Biotic recovery from the end-Permian mass extinction: Analysis of biofabric trends in the Lower Triassic Virgin Limestone, southern Nevada

PDF

Age and sex differences in levels of proliferation within the zebra finch telencephalic ventricular zone

PDF

A unified methodology for seismic waveform analysis and inversion

PDF

Quartz Grain-Shape Variation Within An Individual Pluton: Granite Mountain, San Diego County, California

PDF

Dynamic Development Of Jurassic-Pliocene Cold-Seeps, Convergent Margin Of Western North America

PDF

Application of electrochemical methods in corrosion and battery research

PDF

Chemisorption on the (111) and (100) faces of platinum-tin bimetallic surfaces

Asset Metadata

Creator Grippo, Alessandro (author)

Core Title Cyclostratigraphy and chronology of the Albian stage (Piobbico core, Italy)

School Graduate School

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

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Bottjer, David (committee chair), [illegible] (committee member), Fischer, Alfred G. (committee member), Gorsline, Donn (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c16-635744

Unique identifier UC11335053

Identifier 3116705.pdf (filename),usctheses-c16-635744 (legacy record id)

Legacy Identifier 3116705.pdf

Dmrecord 635744

Document Type Dissertation

Rights Grippo, Alessandro

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