Proxies in Late Cenozoic Paleoceanography (eBook)
862 Seiten
Elsevier Science (Verlag)
978-0-08-052504-4 (ISBN)
* Presents updated techniques and methods in paleoceanography
* Reviews the state-of-the-art interpretation of proxies used for quantitative reconstruction of the climate-ocean system
* Acts as a supplement for undergraduate and graduate courses in paleoceanography and marine geology
The present volume is the first in a series of two books dedicated to the paleoceanography of the Late Cenozoic ocean. The need for an updated synthesis on paleoceanographic science is urgent, owing to the huge and very diversified progress made in this domain during the last decade. In addition, no comprehensive monography still exists in this domain. This is quite incomprehensible in view of the contribution of paleoceanographic research to our present understanding of the dynamics of the climate-ocean system. The focus on the Late Cenozoic ocean responds to two constraints. Firstly, most quantitative methods, notably those based on micropaleontological approaches, cannot be used back in time beyond a few million years at most. Secondly, the last few million years, with their strong climate oscillations, show specific high frequency changes of the ocean with a relatively reduced influcence of tectonics. The first volume addresses quantitative methodologies to reconstruct the dynamics of the ocean andthe second, major aspects of the ocean system (thermohaline circulation, carbon cycle, productivity, sea level etc.) and will also present regional synthesis about the paleoceanography of major the oceanic basins. In both cases, the focus is the "e;open ocean leaving aside nearshore processes that depend too much onlocal conditions. In this first volume, we have gathered up-to-date methodologies for the measurement and quantitative interpretation of tracers and proxies in deep sea sediments that allow reconstruction of a few key past-properties of the ocean( temperature, salinity, sea-ice cover, seasonal gradients, pH, ventilation, oceanic currents, thermohaline circulation, and paleoproductivity). Chapters encompass physical methods (conventional grain-size studies, tomodensitometry, magnetic and mineralogical properties), most current biological proxies (planktic and benthic foraminifers, deep sea corals, diatoms, coccoliths, dinocysts and biomarkers) and key geochemical tracers (trace elements, stable isotopes, radiogenic isotopes, and U-series). Contributors to the book and members of the review panel are among the best scientists in their specialty. They represent major European and North American laboratories and thus provide a priori guarantees to the quality and updat of the entire book. Scientists and graduate students in paleoclimatology, paleoceanography, climate modeling, and undergraduate and graduate students in marine geology represent the target audience. This volume should be of interest for scientists involved in several international programs, such as those linked to the IPCC (IODP Integrated Ocean Drilling Program; PAGES Past Global Changes; IMAGES Marine Global Changes; PMIP: Paleoclimate Intercomparison Project; several IGCP projects etc.), That is, all programs that require access to time series illustrating changes in the climate-ocean system. - Presents updated techniques and methods in paleoceanography- Reviews the state-of-the-art interpretation of proxies used for quantitative reconstruction of the climate-ocean system- Acts as a supplement for undergraduate and graduate courses in paleoceanography and marine geology
Cover 1
Copyright page 5
Contents 8
Contributors 14
Scientific Committee 18
Methods in Late Cenozoic Paleoceanography: Introduction 20
1. Tracers and Proxies in Deep-Sea Records 21
2. Overview of Volume Content 22
3. The Need for Multi-tracers and Multi-Proxy Approaches in Paleoceanography 26
4. From the Geological Record to the Sedimentary Signal and the Properties of the Water Column 29
5. How Far Back in Time are the Proxies Effective? 30
6. New Perspectives and Emerging Proxies 32
Acknowledgments 33
References 33
Part 1: Deep-Sea Sediment Properties 36
Chapter 1. Deep-Sea Sediment Deposits and Properties Controlled by Currents 38
1. Introduction 38
2. Sediment Transport and Deposition by Deep-Sea Currents 49
3. Sediment Deposition: Quaternary Records of Flow in Large-Scale Features 57
4. Current Problems and Prospects 64
References 73
Chapter 2. Continuous Physical Properties of Cored Marine Sediments 82
1. Introduction 82
2. Continuous Centimeter-Scale Measurements of Physical Properties 83
3. Continuous Millimeter- to Micrometer-Scale Measurements of Physical Properties 87
4. Recent Applications of Continuous Centimeter- to Millimeter-Scale Physical Properties of Marine Sediments 100
5. Conclusion 110
Acknowledgments 111
References 111
Chapter 3. Magnetic Stratigraphy in Paleoceanography: Reversals, Excursions, Paleointensity, and Secular Variation 118
1. Introduction 119
2. Background 120
3. Soft Sediment Paleomagnetic Methods 122
4. Magnetometers 126
5. Measurements and Magnetizations 128
6. Data Analysis 133
7. Sediment Magnetism 136
8. Development of Paleomagnetic Records 137
9. The Paleomagnetic Record as a Stratigraphic Tool 140
10. Some Perspectives 147
References 149
Chapter 4. Clay Minerals, Deep Circulation and Climate 158
1. Introduction 158
2. Methodology: The Clay Toolbox in Marine Sediments 161
3. Applications: Clays as a Proxy for Paleocirculation 190
4. Some Perspectives 195
Acknowledgements 195
References 195
Chapter 5. Radiocarbon Dating of Deep-Sea Sediments 204
1. Introduction 204
2. Dating Marine Sediments 206
3. Applications of Marine 14C 220
Appendix I „ Internet Resources 223
References 225
Part 2: Biological Tracers and Biomarkers 230
Chapter 6. Planktonic Foraminifera as Tracers of Past Oceanic Environments 232
1. Introduction 232
2. Biology and Ecology of Planktonic Foraminifera 234
3. Planktonic Foraminiferal Proxies 244
4. Modifications After Death 264
5. Perspectives 272
WWW Resources 272
References 273
Chapter 7. Paleoceanographical Proxies Based on Deep-Sea Benthic Foraminiferal Assemblage Characteristics 282
1. Introduction 282
2. Benthic Foraminiferal Proxies: A State of the Art 290
3. Conclusions 325
Acknowledgements 327
4. Appendix 1 327
References 332
Chapter 8. Diatoms: From Micropaleontology to Isotope Geochemistry 346
1. Introduction 346
2. Improvements in Methodologies and Interpretations 351
3. Case Studies 369
4. Conclusion 375
Acknowledgments 377
References 377
Chapter 9. Organic-Walled Dinoflagellate Cysts: Tracers of Sea-Surface Conditions 390
1. Introduction 390
2. Ecology of Dinoflagellates 395
3. Dinoflagellates vs. Dinocysts and Taphonomical Processes (From the Biocenoses to Thanathocenoses) 396
4. Relationships between Dinocyst Assemblages and Sea-Surface Parameters 401
5. The Development of Quantitative Approaches for the Reconstruction of Hydrographic Parameters Based on Dinocysts 414
6. The Use of Dinocysts in Paleoceanography 416
7. Concluding Remarks 417
References 419
Chapter 10. Coccolithophores: From Extant Populations to Fossil Assemblages 428
1. Introduction 428
2. Taxonomy 430
3. Biogeography, Sedimentation, and Biogeochemical Significance 432
4. Current State of Methods 433
5. Examples of Applications 447
Acknowledgments 451
References 452
Chapter 11. Biomarkers as Paleoceanographic Proxies 460
1. Preliminary Considerations 460
2. Methodological Approaches 462
3. Applications 485
4. Concluding Remarks 493
Acknowledgments 495
References 495
Chapter 12. Deep-Sea Corals: New Insights to Paleoceanography 510
1. Introduction 510
2. Methods and Interpretations 514
3. Landmark Studies 533
References 535
Chapter 13. Transfer Functions: Methods for Quantitative Paleoceanography Based on Microfossils 542
1. Introduction 542
2. Methods Based on Calibration 546
3. Methods Based on Similarity 552
4. Comparison of Methods with a Worked Example 556
5. Discussion and Future Developments 564
6. The applications of Transfer Functions Sensu Lato in Paleoceanography 569
7. Concluding Remarks 575
References 576
Part 3: Geochemical Tracers 584
Chapter 14. Elemental Proxies for Palaeoclimatic and Palaeoceanographic Variability in Marine Sediments: Interpretation and Application 586
1. Introduction 587
2. Sedimentary Components of Marine Sediments 588
3. Normalization of Elemental Data 588
4. Palaeoclimatic Records from the Sea Floor 590
5. Metalliferous Sedimentation in the Ocean 600
6. Elemental Proxies for Palaeoproductivity 604
7. Proxies for Redox Conditions at the Sea Floor and in Bottom Sediments 618
8. Future Developments 640
9. Afterword 644
Acknowledgements 644
References 644
Chapter 15. Isotopic Tracers of Water Masses and Deep Currents 664
1. Introduction 664
2. Present State of Methodological Approaches and Interpretations 667
3. Examples of Applications 683
4. Conclusion and Perspectives 689
References 690
Chapter 16. Paleoflux and Paleocirculation from Sediment 230Th and 231Pa/230Th 700
1. Introduction 700
2. Factors Controlling the Distribution of 230Th and 231Pa in the Ocean 703
3. Paleoceanographic Applications 717
4. Conclusions 731
References 731
Chapter 17. Boron Isotopes in Marine Carbonate Sediments and the pH of the Ocean 736
1. Introduction 736
2. Empirical Observations and Theoretical Background 737
3. Caveats and Complications 740
4. Applications of the Boron Isotope Paleo-pH Proxy 745
5. Summary and Conclusion 749
Acknowledgments 750
References 750
Chapter 18. The Use of Oxygen and Carbon Isotopes of Foraminifera in Paleoceanography 754
1. Introduction 754
2. Notation and Standards 755
3. Stratigraphic and Paleoecological Use of Foraminifera 757
4. Foraminiferal Oxygen Isotopes as Environmental Proxies 759
5. Foraminiferal Carbon Isotopes as Environmental Proxies 770
6. Conclusion and Summary 778
References 779
Chapter 19. Elemental Proxies for Reconstructing Cenozoic Seawater Paleotemperatures from Calcareous Fossils 784
1. Introduction 784
2. Thermodynamic Effects on Mg Co-Precipitation in Calcites 785
3. Foraminiferal Mg/Ca Paleothermometry 786
4. Ostracode Mg/Ca Paleothermometry 796
5. Coralline Sr/Ca Paleothermometry 799
6. Contributions to Cenozoic Climate History 803
References 809
Reconstructing and Modeling Past Oceans 818
1. A Brief Historical Overview 819
2. Classification of Climate Models 820
3. Models and Proxy Data 823
4. International Programs 826
5. Conclusion 827
References 828
Index of Taxa 832
Subject Index 836
Chapter One Deep-Sea Sediment Deposits and Properties Controlled by Currents
Publisher Summary
This chapter focuses on the deep-sea sediment deposits and properties controlled by currents. Initial recognition of the importance of deep currents in redistributing sediments came from the combination of: (1) photographic evidence for bedforms under known currents, (2) photographic evidence for bedforms under known currents, (3) acoustic profiler data from echo-sounder and 3.5 kHz, and (4) seismic reflection profiles documenting large sediment bodies under current systems. Deep-sea sediments normally show few structures other than biological disturbance, therefore, grain size parameters have been used as the best indicator of relative flow speed. The deep circulation does not deliver sediment to the ocean, but reworks it once it has arrived. Sediment delivery is mainly by gravity-driven processes. In the open ocean far from land, pelagic sinking flux is rapid—on a timescale of several tens of days — because of particle aggregation and biological packaging. Close to continental margins, sediment is carried downslope in copious quantities by turbidity currents and debris flows that are responsible for construction of much of the continental rise. Gravity flows do not deliver sediment bearing a pure signature characteristic of conditions in the source area at the time they were triggered. Strong deep-sea currents resuspend this sediment, forming nepheloid layers, and move it to areas of spatial decrease in flow speed, causing deposition. The chapter discusses the biological indicators of flow speed, global ocean flow patterns, sediment transport and deposition by deep-sea currents, and current problems and prospects.
1 Introduction
Sediments carry diverse types of information in their composition and grain size. An enormous number of chemical and isotopic attributes have been used to deduce environments of deposition and sediment production with particular emphasis on climatic variables. In many instances the bulk of the sediment is just seen as a carrier phase for the main information provider, often foraminifera. This attitude has led to several interpretational problems, e.g. in age modelling, which could be avoided by considering the whole sediment and the processes by which it is delivered, sorted and deposited. This topic and the interpretation of the vigour of the depositing flow are treated here.
1.1 Current Indicators in Deep-Sea Sediments
Initial recognition of the importance of deep currents in redistributing sediments came from the combination of:
1) Photographic evidence for bedforms under known currents (Heezen & Hollister, 1964),
2) Sedimentary structures in cores under strong currents (Hollister & Heezen, 1972),
3) Acoustic profiler data from echo-sounder and 3.5 kHz (Schneider et al., 1967), and
4) Seismic reflection profiles documenting large sediment bodies under current systems (Johnson & Schneider, 1969; Jones, Ewing, Ewing, & Eittreim, 1970).
1.1.1 Photographs
Systematic regional examination of photographs shows spatial variability of flow (Tucholke, Hollister, Biscaye, & Gardner, 1985) (Figure 1) and has yielded an ordinal scale of current intensity shown by photographed bedforms (McCave & Tucholke, 1986). Although these show the zonation of current speed very well by progression from subtle smoothing through longitudinal ripples to barchan ripples and crag-and-tail structure, this is virtually useless below the surface. The pervasive structure of muddy contourite sediments is bioturbation (Wetzel, 1991; Baldwin & McCave, 1999; Löwemark, Schönfeld, Werner, & Schafer, 2004 show X-radiographs). This destroys virtually all traces of original depositional structure.
Figure 1 Current zonation of Nova Scotian Rise deduced from bedforms seen in bottom photographs. Based on data in Tucholke et al. (1985). Key to photographic indicators of increasing flow speed: W/T=weak/tranquil, INT=intermediate, LR=longitudinal ripples, Cloudy=photos showing turbid water due to resuspension. The HEBBLE instrument deployments and cores were around 40°27′N, 62°20′ W.
1.1.2 Sedimentary structures
A few contourites show clear sedimentary structure (Figure 2), but these are relatively sandy (e.g. shown is 60–80% >63 μm). The sand (mainly foraminifera) content of many contourites is in the region of 10–20%, decreasing with increasing accumulation rate. In the case of a S.W. Indian Ocean core WIND 27K the sand percentage is 25–40% with an accumulation rate of ∼3 cm ka−1 for the period 0–60 ka. Over a 20 cm thick section shown in Figure 2, the sand percentage goes up to 80% and the structure is ripple cross-lamination. Our best estimate is that this section represents from 125 to 60 ka, a mean sedimentation rate of 0.3 cm ka−1, considerably less and certainly not continuous. The current is inferred to have strengthened sufficiently to rework the section from stages 4 down to 5e, possibly in a couple of high-speed pulses lasting a few thousand years at the 5e–5d and 5a–4 transitions (McCave, Kiefer, Thornalley, & Elderfield, 2005). This demonstrates the fact that the stratigraphic resolution of sandy contourites is likely to be shot through with hiatuses. High (foram) sand contents are generally due to either dissolution of fine carbonate or winnowing removal of fine sediment.
Figure 2 X-radiograph of core WIND 27K, 165-198 cm, from the Amirante Passage, equatorial western Indian Ocean, showing cross-laminated contourite muddy foraminiferal sand. Note that the base is sharp but deformed during coring and that the top is gradational in texture. Fine-scale lamination, cross lamination and erosion surfaces are evident. This 20 cm represents around 40,000 yr, demonstrating the stratigraphic penalty of too-high current speed.
1.1.3 Acoustic profiles
Mapping of echo character from 10 kHz sounders also showed current zonation on the margin (Hollister & Heezen, 1972), but this was superseded by the now ubiquitous 3.5 kHz whose interpretation was systematised by workers at Lamont in the 1970s (Damuth, 1980). The combination of high frequency echo sounder (10–20 kHz) and 3.5 kHz profiler can be revealing (Figure 3) (Winn, Kogler, & Werner, 1980), because the strength of the acoustic return is related to the surface sediment density (porosity) and grain size, which is a function of net accumulation rate, involving both deposition and winnowing. As can be seen from Figure 3, there is a spatially coherent response of sedimentation rate and reflectivity (mainly porosity) to current flow.
Figure 3 (Upper) 3.5 kHz WNW-ESE profile across northern Gardar Drift at 60° N, 23° W showing reduced sedimentation rate on the eastern slope of the drift by closer spaced reflectors. (Lower) 10 kHz echo sounder record along the same track showing higher amplitude reflection (redder colour) of the ‘harder’ sea bed more strongly affected by currents, corresponding to coarser size and slower net accumulation rate (from McCave, 1994). Coarser sediments occur on the eastern side of the drift compared with the western side where they are finer (Bianchi & McCave, 2000, their Figure 19).
1.1.4 Seismic reflection profiles
Early seismic reflection profiling showed several drifts to be thick piles of current – deposited deep-sea sediments, e.g. Blake Outer Ridge, Eirik Drift, Feni Drift (Johnson & Schneider, 1969; Jones et al., 1970) (Figure 4). Over the years the number of drifts so recognised has increased greatly, diagnostic seismic characters have been documented (Faugères, Stow, Imbert, Viana, & Wynn, 1999) and several edited volumes of records have been devoted to them (e.g. Rebesco & Stow, 2001; Stow, Pudsey, Howe, Faugeres, & Viana, 2002). Common large bedforms on drifts are sediment waves with wavelengths of 1–5 km, imaged by seismic reflection, to which much attention has also been paid (Mienert, Flood, & Dullo, 1994; Wynn & Stow, 2002). Some waves on continental margins are deposited under turbidity currents, some under usually geostrophic currents, thereby setting a trap for the unwary. Distinction is not easy as both usually migrate up current; but, whereas turbidite waves are generally perpendicular to flow and nearly parallel with contours while contourite waves are oblique to flow, the flow direction is often unknown and the strike of low amplitude mud waves needs high quality swath bathymetry to be detected. One large fan is made of mud turbidites that have been entrained in a deep western boundary current, and thus termed a ‘fan-drift’ (Carter & McCave, 1994, 2002), while another is made of contourites and called a ‘contourite fan’...
| Erscheint lt. Verlag | 25.5.2007 |
|---|---|
| Sprache | englisch |
| Themenwelt | Naturwissenschaften ► Geowissenschaften ► Geologie |
| Naturwissenschaften ► Geowissenschaften ► Hydrologie / Ozeanografie | |
| Naturwissenschaften ► Geowissenschaften ► Mineralogie / Paläontologie | |
| Naturwissenschaften ► Physik / Astronomie | |
| Technik | |
| ISBN-10 | 0-08-052504-0 / 0080525040 |
| ISBN-13 | 978-0-08-052504-4 / 9780080525044 |
| Haben Sie eine Frage zum Produkt? |
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