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University of Southampton Research Repository ePrints Soton Copyright © and Moral Rights for this thesis are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder/s. The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders. When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given e.g. AUTHOR (year of submission) "Full thesis title", University of Southampton, name of the University School or Department, PhD Thesis, pagination http://eprints.soton.ac.uk UNIVERSITY OF SOUTHAMPTON FACULTY OF ENGINEERING, SCIENCE & MATHEMATICS School of Ocean & Earth Science High Resolution Palaeoceanography and Palaeoclimatology from Mid and High Latitude Late Cretaceous Laminated Sediments by Andrew Davies Thesis for the degree of Doctor of Philosophy March 2006 Graduate School of the National Oceanography Centre, Southampton This PhD dissertation by Andrew Davies has been produced under the supervision of the following persons Supervisor/s Prof. Alan E.S. Kemp Dr John Barron Dr Jennifer Pike Chair of Advisory Panel Prof. Andrew Roberts Member/s of Advisory Panel Dr Paul Wilson UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF ENGINEERING, SCIENCE & MATHEMATICS SCHOOL OF OCEAN & EARTH SCIENCES Doctor of Philosophy HIGH RESOLUTION PALAEOCEANOGRAPHY AND PALAEOCLIMATOLOGY FROM MID AND HIGH LATITUDE LATE CRETACEOUS LAMINATED SEDIMENTS by Andrew Davies Late Cretaceous laminated diatomaceous sediments from the Marca Shale (California) and CESAR 6 core (Arctic Ocean) have been analysed using scanning electron microscopy techniques and found to contain marine varves. The varve interpretation is based on the pervasive occurrence of laminae types that can be related to different seasons and placed into robust annual flux cycles. In the Marca Shale this consists of intermittent near-monospecific laminae of Azpeitiopsis morenoensis deposited in the late summer, succeeded by a ‘fall dump’ mixed assemblage laminae, dominated by fragmented Hemiaulus polymorphus, Stephanopyxis spp. and Stellarima spp.. Intermittent near- monospecific Chaetoceros-type resting spore laminae, deposited in spring follow and are in turn overlain by terrigenous laminae, reflecting enhanced fluvial runoff during the summer. A mixed floral diatomaceous and terrigenous laminae couplet constitute the annual flux cycle in the majority of varves. Summer terrigenous flux may indicate that the ~43°N palaeolatitude estimate is incorrect, and deposition actually occurred at lower latitudes or alternatively, that the Marca basin was influenced by intense monsoonal summer storms. The CESAR 6 annual flux cycle consists of alternating diatom resting spore and vegetative cell laminae (often dominated by Hemiaulus), interpreted to represent spring bloom flux and ‘fall dump’/intermittent summer blooms flux, respectively. Near-monospecific Rhizosolenia laminae frequently occur above vegetative laminae, relating to subsequent ‘fall dump’ flux. Common silicoflagellate/setae-rich laminae, often containing diatom hash, occur beneath resting spore laminae, interpreted as the early spring flux of silicoflagellate blooms and grazed diatoms. Seasonally occurring detrital ‘blebs’ and rare detrital laminae are also observed, which may represent ice rafted debris, consistent with Campanian model simulations. Diatom taxa adapted to exploit stratified conditions, sedimented over the summer or in a ‘fall dump’, are important components of both sequences. Spring bloom flux was important in the CESAR 6, but was only a subsidiary component in the Marca Shale. The abundance of Hemiaulus spp. at both localities may be evidence for diatom blooms powered by N2-fixing cyanobacteria. Diatom biostratigraphy indicates a late Late Campanian age for the CESAR 6, although an earliest Maastrichtian age cannot be discounted. Time-series analysis of laminae thickness data from both sequences and bioturbation index data from the Marca Shale, reveal both sites contain strong quasi-biennial signals (mean periodicities of 27.4 and 30.4 months, respectively), inferred to relate to the Quasi-Biennial Oscillation (QBO). The CESAR 6 contains strong sub-decadal/quasi-decadal peaks interpreted to relate to Northern Hemisphere Annular Mode (NAM) variability. Together with the QBO signals, this suggests NAM variability was robust during the Late Cretaceous. Similar frequency peaks occur in the Marca Shale which, supported by several sedimentological lines of evidence, indicates the presence of an El Niño Southern Oscillation (ENSO)-like oscillation. Theory dictates that a weakening of the ‘Bjerknes’ feedback loop in the equatorial Pacific will lead to a reduction or shutdown of ENSO variability, resulting in a permanent El Niño climate. The Late Cretaceous was witness to a severe weakening of the ‘Bjerknes’ feedback, yet the results of this study demonstrate that there was robust ENSO variability during this greenhouse period, adding to the evidence against permanent ‘El Niño’ climate states. A 10.66 year harmonic peak in the CESAR 6 is taken as evidence for modulation of the NAM by solar variability. Peaks at 10.0, 10.3 and 10.8 years in the Marca Shale are interpreted to relate to the solar modulation of strong ENSO events. Both sites also contain multi-decadal peaks, the frequency of which may also have been modulated by solar variability. Quasi-bidecadal peaks are inferred to relate to the NAM or an oscillation analogous to the Pacific Decadal Oscillation (PDO), possibly influenced by the Hale cycle. A 44 year peak in the Marca Shale is also inferred to relate to the PDO. The CESAR 6 contains a harmonic peak at 78.74 years, interpreted to relate to modulation of the NAM over the Gleissberg solar cycle or alternatively, to modulation of the PDO. Contents LIST OF CONTENTS List of Figures . v List of Tables . xii List of Plates . xiv Authors Declaration . xvi Acknowledgments . xvii CHAPTER 1-Introduction . 1 1.1 INTRODUCTION . 1 1.2 BACKGROUND . 1 1.2.1 Rationale . 1 1.2.2 Upper Cretaceous diatomaceous sediments . 3 1.2.3 Marca Shale . 3 1.2.4 CESAR 6 . 3 1.3 OBJECTIVES OF THE STUDY . 4 1.4 STRUCTURE OF THE THESIS . 4 CHAPTER 2-Methodology . 6 2.1 INTRODUCTION . 6 2.2 METHOD OF MAKING SLIDES FOR BSEI . 6 2.2.1 Resin embedding lithified (Marca Shale) samples . 6 2.2.2 Resin embedding unconsolidated (CESAR 6) samples . 7 2.2.2.1 Chemical drying of the sediment . 7 2.2.2.2 Resin embedding . 7 2.2.3 Preparation of polished thin sections . 9 2.3 SCANNING ELECTRON MICROSCOPY . 9 2.3.1 Backscattered electron imagery (BSEI) . 10 2.3.2 Peel slides . 10 2.3.3 Secondary electron imagery (SEI) . 11 2.4 MEASUREMENTS FROM SEM IMAGES . 11 2.5 DIATOM STREW SLIDE PREPARATION . 11 2.6 X-RAY DIFFRACTION (XRD) . 13 2.6.1 Bulk mineral analysis . 13 2.6.2 Clay mineral analysis . 13 2.7 MAGNETOSTRATIGRAPHIC ANALYSIS . 13 CHAPTER 3-Ecology of the Diatom Flora Preserved in the Late Cretaceous Marca Shale and CESAR 6 Core . 14 3.1 INTRODUCTION . 14 3.2 Class COSCINODISCOPHYCEAE (centric diatoms) Round & Crawford . 16 3.2.1 Genus Thalassiosiropsis Hasle in Hasle & Syvertsen . 16 3.2.2 Genus Gladiopsis Gersonde & Harwood . 17 3.2.3 Genus Stephanopyxis (Ehrenberg) Ehrenberg . 17 3.2.4 Genus Triceratium Ehrenberg . 18 3.2.5 Genus Paralia Heiberg . 21 3.2.6 Genus Actinoptychus Ehrenberg . 21 3.2.7 Genus Coscinodiscus Ehrenberg . 22 3.2.8 Genus Trochosiropsis Gleser . 22 3.2.9 Genus Skeletonemopsis Sims . 23 3.2.10 Genus Stellarima Hasle & Sims . 26 3.2.11 Genus Azpeitiopsis Sims . 27 i Contents 3.2.12 Genus Hemiaulus Ehrenberg . 27 3.2.13 Genus Cerataulina Pergallo . 29 3.2.14 Genus Trinacria Heiberg . 37 3.2.15 Genus Medlinia Sims . 37 3.2.16 Genus Anaulus Ehrenberg . 38 3.2.17 Genus Chasea Hanna . 38 3.2.18 Rhizosolenids (Rhizosolenia and Proboscia) . 39 3.2.18.1 Genus Rhizosolenia Brightwell . 39 3.2.18.2 Genus Proboscia Sundström . 40 3.3 Class FRAGILARIOPHYCEAE (araphid pennate diatoms) Round . 42 3.3.1 Genus Helminthopsis Van Heurck . 42 3.3.2 Genus Sceptroneis Ehrenberg . 42 3.4 TAXA OF UNCERTAIN SYSTEMATIC POSITION . 42 3.4.1 Genus Pseudopyxilla Forti . 42 3.4.2 Genus Pterotheca Grunow ex Forti . 47 3.5 RESTING SPORES . 47 3.5.1 Chaetoceros spp.-type spores . 47 3.5.2 Hemiaulus tumidicornis . 48 3.5.3 Hemiaulus sp. 1 . 48 3.5.4 Spore ‘3’ . 49 3.5.5 Skeletonema subantarctica . 49 3.5.6 Genus Goniothecium Ehrenberg . 52 3.5.7 Genus Odontotropis Grunow . 52 3.6 DISCUSSION . 53 3.6.1 Taphonomic effects on the diatom assemblages . 53 3.6.2 Diatom species not included in previously published floral lists. 55 3.6.2.1 Marca Shale . 55 3.6.2.2 CESAR 6 . 55 3.6.3 Comparisons of the diatom flora of the Marca Shale and CESAR 6 . 55 CHAPTER 4-Sedimentology and High-Resolution Analysis of the Marca Shale Microfabric . 58 4.1 INTRODUCTION . 58 4.1.1 Locality and Stratigraphy . 59 4.1.2 Palaeogeographic Setting . 61 4.1.3 Palaeoclimate . 62 4.2 MATERIALS AND METHODS . 64 4.3 RESULTS . 65 4.3.1 Diatomaceous laminae . 69 4.3.2 Diatoms in early diagenetic nodules . 72 4.3.3 Terrigenous laminae . 73 4.3.4 Higher level of complexity within the laminated fabric . 75 4.3.5 Clay mineralogy . 78 4.3.6 Laminae thickness variations . 79 4.3.7 Foraminifera . 81 4.3.8 Pelletal structures . 82 4.3.9 Bioturbation . 85 4.3.10 ‘Event beds’ and vein structures . 88 4.3.11 Magnetostratigraphy . 91 4.4 INTERPRETATION AND DISCUSSION . 91 4.4.1 Clay mineralogy and inferences on the cause of the alternating dark/pale coloured units .