Reconstructing Quaternary Environments Second Edition

J.J. LOWE Professor of Geography and Quaternary Science Centre for Quaternary Research Royal Holloway University of London

M.J.C. WALKER Professor of Physical Geography University of Wales Lampeter

P-4 LONGMAN Contents

Preface to the first edition xv Preface to the second edition xvii Acknowledgements xix

Chapter 1 The Quaternary record 1 1.1 Introduction 1 1.2 The character of the Quaternary 1 1.3 The duration of the Quaternary 2 1.4 The development of Quaternary studies 3 1.4.1 Historical developments 3 1.4.2 Recent developments 7 1.5 The framework of the Quaternary 8 1.6 The causes of cl imatic change 12 1.7 The scope of this book 16 Notes 16

Chapter 2 Geomorphological evidence 18 2.1 Introduction 18 2.2 Methods 18 2.2.1 Field methods 18 2.2.2 Remote sensing 21 2.3 Glacial landforms 23 2.3.1 Extent of ice cover 23 2.3.2 Geomorphological evidence and the extent of ice sheets and glaciers during the last cold stage 26 2.3.3 Direction of ice movement 33 2.3.4 Recon.stniction of former ice masses 38 2.3.5 Palaeotemperature estimates from glacial geomorphological evidence 44 2.4 Periglacial landforms 50 2.4.1 Palaeoclimatic inferences based on periglacial landforms 51 2.5 Sea-level change 53 2.5.1 Relative and 'absolute' sea-level changes 54 2.5.2 Eustatic changes in sea level 55

vll 2.5.3 Tectonic influences 61 2.5.4 Shoreline sequences in areas affected by glacio-isostasy 62 2.5.5 Palaeoenvironmental significance of sea-level changes 65 2.6 River terraces 68 2.6.1 Origins of river terraces 70 2.6.2 River terraces and palaeoenvironments 72 2.6.3 The terraces of the River Thames 72 2.7 Quaternary landforms in low latitudes 77 2.7.1 Pluvial lakes 78 2.7.2 Dunefields 80 2.7.3 Fluvial landforms 83 2.7.4 Weathering crusts 83 2.8 Conclusions 84 Notes 84

Chapter 3 Lithological evidence 85 3.1 Introduction 85 3.2 Field and laboratory methods 85 3.2.1 Sediment sections 85 3.2.2 Coring 86 3.2.3 Laboratory methods 86 3.3 Glacial sediments 88 3.3.1 Introduction 88 3.3.2 The nature of glacial sediments 89 3.3.3 The classification of tills 90 3.3.4 The influence of the thermal regime of glacier ice 94 3.3.5 Analysis of glacigenic sequences 95 3.3.6 Ice-directional indicators 97 3.4 Periglacial sediments 102 3.4.1 Introduction 102 3.4.2 Structures associated with permafrost 102 3.4.3 Palaeoclimatic significance of periglacial structures 105 3.5 Palaeosols 109 3.5.1 Introduction 109 3.5.2 The nature of palaeosols 110 3.5.3 Analysis of palaeosols 111 3.5.4 Palaeosols and Quaternary environments 113 3.6 Lake level records from low latitude regions 114 3.6.1 Introduction 114 3.6.2 'Pluvial'lake sediment sequences 115 3.6.3 Lake level changes and Quaternary palaeoclimates 118 3.7 Wind-blown sediments 121 3.7.1 Introduction 121 3.7.2 Loess stratigraphy 121 3.7.3 Mid-latitude sand belts (coversands) 124 Contents ix

3.7.4 Low latitude'sand seas' 124 3.7.5 Wind-blown sediments and palaeoenvironmental reconstructions 125 3.8 Cave sediments and carbonate deposits 127 3.8.1 Introduction 127 3.8.2 Detrital sediment in caves 127 3.8.3 Speleotbem 129 3.8.4 Speleotbem growth and environmental reconstruction 131 3.8.5 Oxygen isotope ratios in cave speleotbem 132 3.8.6 Other carbonate deposits 135 3.9 Lake, mire and bog sediments 135 3.9.1 Introduction 135 3.9.2 The nature of lake and bog sediments 137 3.9.3 Palaeoenvironmental evidence from lake sediments 141 3.9.4 Palaeoenvironmental evidence from mire and bog sediments 146 3.10 Stable oxygen isotope stratigraphy of deep-sea sediments 148 3.10.1 Introduction 148 3.10.2 Oxygen isotope ratios and the ocean sediment record 149 3.10.3 Environmental influences on '^0/"'0 ratios in marine sediments 151 3.10.4 Limitations in oxygen isotope analysis 153 3.10.5 Carbon isotopes in marine sediments . 154 3.11 Ice-core stratigraphy 154 3.11.1 Introduction 154 3.11.2 Ice masses as palaeoenvironmental archives 155 3.11.3 Analysis of ice cores 155 3.11.4 Palaeoenvironmental significance of ice-core data 158 3.12 Conclusions 160 Notes 160

Biological evidence 162 4.1 Introduction 162 4.1.1 The nature of the Quaternary fossil record 162 4.1.2 The taphonomy of Quaternary fossil assemblages 162 4.1.3 The interpretation of Quaternary fossil ii:.: assemblages 163 4.2 Pollen analysis 163 4.2.1 Introduction 163 4.2.2 The nature of pollen and spores 164 4.2.3 Field and laboratory work 165 4.2.4 Pollen diagrams 165 4.2.5 The interpretation of pollen diagrams 169 4.2.6 Applications of pollen stratigraphy 173 Contents

4.3 Diatom analysis 175 4.3.1 Introduction 175 4.3.2 The nature and ecology of diatoms 176 4.3.3 Field and laboratory methods 176 4.3.4 The interpretation of Quaternary diatom records 177 4.3.5 Applications of diatom analysis 177 4.4 Plant macrofossil analysis 182 4.4.1 Introduction 182 4.4.2 The nature of plant macrofossils 182 4.4.3 Field and laboratory work 184 4.4.4 Data presentation 184 4.4.5 The interpretation of plant macrofossil data 185 4.4.6 Applications of plant macrofossil studies 189 4.5 Fossil insect remains 191 4.5.1 Introduction 191 4.5.2 Coleoptera 192 4.5.3 Laboratory methods 192 4.5.4 Coleopteran analysis and Quaternary environments 192 4.6 Chironomidae 200 4.7 Non-marine Mollusca 202 4.7.1 Introduction 202 4.7.2 The nature and distribution of molluscs 203 4.7.3 Field and laboratory work 203 4.7.4 Taphonomy of non-marine molluscan assemblages 204 4.7.5 Habitat preferences of non-marine Mollusca 205 4.7.6 Non-marine Mollusca and palaeoclimate reconstructions 207 4.8 Marine Mollusca 208 4.8.1 Introduction 208 4.8.2 Analysis of marine molluscan assemblages 210 4.8.3 Marine Mollu.sca and palaeoclimatic inferences 211 4.9 Ostracod analysis 212 4.9.1 The nature and distribution of ostracods 212 4.9.2 Collection and identification 212 4.9.3 Ostracoda in Quaternary studies 213 4.10 Foraminiferal analysis 215 4.10.1 The nature and distribution of Foraminifera 215 4.10.2 Collection and identification 215 4.10.3 Foraminifera in Quaternary inshore and shelf sediments 215 4.11 Micropalaeontology of deep-sea sediments 218 4.11.1 Introduction 218 4.11.2 Radiolaria 218 4.11.3 Coccolithophores 219 4.11.4 Marine microfossils jn ocean sediments 219 4.11.5 Laboratory separation of marine microfossils 220 Contents xi

4.11.6 Marine palaeoclimatology 220 4.11.7 Marine palaeoproductivity and palaeocirculation 225 4.12 Vertebrate remains 225 4.12.1 Introduction 225 4.12.2 The structure of teeth and bones 227 4.12.3 Fossilisation of bone material 227 4.12.4 Field and laboratory techniques 228 4.12.5 The taphonomy of fossil vertebrate assemblages 228 4.12.6 Vertebrate fossils and Quaternary environments 230 4.13 Other fossil groups 231 4.13.1 Chrysophytes 231 4.13.2 Cladocera 231 4.13.3 Coral polyps 231 4.13.4 Fungal remains 231 4.13.5 'Rhizopods'or testate amoebae 232 4.14 Multi-proxy palaeoecological studies 232 4.15 Quaternary palaeobiology and ecological theory 233 4.15.1 Biomass and global climate change 233 4.15.2 Migration of biota and community structures 233 4.15.3 Extinctions 234 4.15.4 Conservation, biodiversity and habitat destruction 235 4.16 Conclusions 235 Notes 236

Chapter 5 Dating methods 237 5.1 Introduction 237 5.2 Precision and accuracy in Quaternary dating 237 5.3 Radiometric dating techniques 238 5.3.1 The nucleus and radioactivity 238 5.3.2 Radiocarbon dating 240 5.3.3 Potassium-argon and argon-argon dating 248 -V.;;.!. 5.3.4 Uranium-series dating 250 5.3.5 Fission track dating 254 5.3.6 Luminescence dating 255 5.3.7 Electron spin resonance (FSR) dating 256 . -m 5.3.8 Other radiometric methods 257 5.4 Incremental dating methods 259 5.4.1 Dendrochronology 259 'jHs :^ 5.4.2 Varve chronology 266 " li! 5.4.3 Lichenometry 273 5.4.4 Annual layers in glacier ice 274 ri: i 5.5 Age-equivalent stratigraphic markers 274 5.5.1 Palaeomagnetism 275 :• os.ife 5.5.2 Tephrochronology 280 5.5.3 Oxygen isotope chronology 284 5.6 Relative chronology based on processes of chemical alteration 285 Contents

5.6.1 Ami no-acid geochronology 285 5.6.2 Fluorine, uranium and nitrogen content of fossil bones 291 5.6.3 Obsidian hydration 293 5.6.4 Weathering characteristics of rock surfaces 293 5.6.5 Pedogenesis 294 5.7 Conclusions 296 Notes 297

Chapter 6 Approaches to Quaternary stratigraphy and correlation 298 6.1 Introduction 298 6.2 Stratigraphic subdivision 298 6.2.1 Principles of Quaternary stratigraphy 298 6.2.2 Stratotypes 299 6.2.3 Elements of Quaternary stratigraphy 300 6.3 Time-stratigraphic correlation 309 6.3.1 Principles of Quaternary correlation 309 6.3.2 Elements of time-stratigraphic correlation 311 6.3.3 Correlation between continental, marine and ice-core records 313 6.4 Conclusions 322 Note 323

Chapter 7 The last interglaclal-glacial cycle: 130-10 ka BP 324 7.1 Introduction 324 7.2 The stratigraphic framework for the last 130ka 325 7.3 The last interglacial (Ol sub.stage 5e) 326 7.3.1 Defining the last interglacial 326 7.3.2 Proxy records from the last interglacial 327 7.3.3 Dating the last interglacial 327 7.4 The transition to the last cold stage (Ol substages 5d to 5a) 330 7.4.1 The Ol substage 5e/5d transition 330 7.4.2 01 substages 5c to 5a 332 7.4.3 The Ol stage 5/4 transition 333 7.4.4 Short-lived 'events' during the last interglacial- glacial transition 334 7.5 The last cold stage (Ol stages 4 to 2) 334 7.5.1 Events during the last cold stage: the marine record 33-^ 7.5.2 Events during the last cold stage: the terrestrial record 336 7.5.3 Events during the last cold stage: the ice-sheet record 337 7.5.4 Events during the last cold stage: the ice-core record 340 7.5.5 Correlation between ice-core, marine, terrestrial and glacial records from the last cold stage 340 Contents xiil

7.6 The last glacial-interglacial transition (OI stage 2/1) 342 7.6.1 Stratigraphic nomenclature 342 7.6.2 Events during the last glacial-interglacial transition: the terrestrial record 343 7.6.3 Environmental changes during the last glacial- interglacial transition: the marine record 351 7.6.4 Ice-core records of environmental changes during the last glacial-interglacial transition 352 7.6.5 Correlation between terrestrial, marine and ice-core records of the last glacial-interglacial transition 353 7.7 Atmospheric circulation: global circulation models 357 7.7.1 Global circulation models (GCMs) 357 7.7.2 Setting the boundary conditions for GCMs 357 7.7.3 Running GCM experiments 358 7.7.4 Limitations of GCMs 360 7.7.5 The importance of GCMs 360 7.8 The search for causes 361 7.8.1 The Astronomical Theory of climatic change 361 7.8.2 Palaeoceanography and climatic change 362 7.8.3 Ice-sheet/glacier fluctuations and climatic change 364 7.8.4 Variation in atmospheric gas content and climatic change 365 7.8.5 Volcanic activity and climatic change 367 7.8.6 Variations in solar output and climatic change 368 7.8.7 Geodynamic factors 369 7.8.8 Conceptual models of Late Quaternary climatic change 370 7.9 Concluding remarks 371 Notes 373

Bibliography 374 Index 434