Paleontology and Geology of Laetoli: Human Evolution in Context (eBook)

Preface 8
Contents 10
Contributors 12
Chapter 1: Laetoli Revisited: Renewed Paleontological and Geological Investigations at Localities on the Eyasi Plateau in Northern Tanzania 16
Introduction 16
History of Paleontological Research at Laetoli 17
Renewed Fieldwork (1998–2006) 19
Field Seasons 20
1998 (July 31–August 25) 20
1999 (January 3–25) 20
2000 (January 16–February 7 and July 8–29) 21
2001 (July 5–28) 21
2003 (July 4–28) 22
2004 (June 25–July 21) 22
2005 (May 27–June 15) 22
Results 22
New Paleontological Collections 22
Geological Investigations 25
Radiometric Age Determinations 26
Paleoecology 26
Systematics and Paleobiology of the Fauna 26
Additional Fossil Hominins 26
Conclusions 27
References 27
Chapter 2: Paleontological Localities on the Eyasi Plateau, Including Laetoli 31
Introduction 31
Paleontological Localities at Laetoli 34
Locality 1 34
Locality 1NW 35
Locality 2 35
Locality 3 37
Locality 4 39
Locality 5 40
Locality 6 40
Locality 7 40
Locality 7E 41
Locality 8 41
Locality 9 41
Locality 9S 42
Locality 10 42
Locality 10W 42
Locality 10E 43
Locality 10NE 43
Locality 11 43
Locality 12 44
Locality 12E 44
Locality 13 45
Locality 14 45
Locality 15 45
Locality 16 46
Locality 17 47
Locality 18 47
Locality 19 49
Locality 20 49
Locality 21 49
Locality 22 49
Locality 22E 49
Locality 22S 50
Locality 23 50
Locality 24 51
Garusi SW 51
Silal Artum 51
Other Paleontological Localities on the Eyasi Plateau 52
Kakesio 52
Kakesio South 53
Emboremony 53
Esere 54
Engesha 54
Lobileita 55
Olaltanaudo 55
Oleisusu 55
Ndoroto 55
Noiti 1-3 55
Conclusions 57
References 58
Chapter 3: Sedimentology, Lithostratigraphy and Depositional History of the Laetoli Area 60
Introduction 60
Lithostratigraphy 61
Overview 61
Laetolil Beds, Lower Unit 62
Laetolil Beds, Upper Unit 63
Ndolanya Beds 63
Ndolanya Beds, Lower Unit 63
Ndolanya Beds, Upper Member 64
General Lithostratigraphy 64
Primary Fall-Out Tuff Correlation 64
Color Change 64
Description of Logged Sections 65
Field Methods 65
Sections and Locations 66
Locality 1 66
Locality 2 66
Locality 3 67
Locality 4 68
Locality 5 68
Locality 6 69
Localities 7 and 7E 69
Locality 8 70
Locality 9S 71
Localities 10, 10W, 10E and 10NW 73
Locality 12 and 12E 74
Locality 13 75
Locality 14 77
Locality 15 77
Locality 16 77
Locality 18 78
Locality 19 78
Locality 20 79
Locality 21 79
Localities 22 and 22E 79
Sedimentary Litho-Facies and Depositional Environments 80
Aeolian Tuff 82
Water Worked Tuff 86
Fluvial Tuff 86
Pond Deposits 87
Air Fall Tuff 87
Discussion and Summary 87
References 88
Chapter 4: 40Ar/39Ar Dating of Laetoli, Tanzania 90
Introduction 90
Previous Research 90
Methodology 92
Dating Results Overview 93
K-Feldspar 93
Biotite 93
Hornblende 99
Chronostratigraphy 99
Lower Laetolil Beds 99
Upper Laetolil Beds 101
Ndolanya Beds 105
Naibadad Beds 106
Olpiro Beds 107
Sedimentation History of the Upper Laetolil Beds 107
Conclusions 108
References 109
Chapter 5: Petrology, Geochemistry and Age of Satiman, Lemagurut and Oldeani: Sources of the Volcanic Deposits of the Laetoli Area 111
Introduction 111
Methods 112
Field Methods 112
Laboratory Methods 113
Major Element Analyses 113
Sr and Nd Isotopes 113
Mineral Phase Analyses 113
40Ar/39Ar Dating 113
Results 117
Discussion 124
Source and Crustal Influence 124
Geochronology 125
Oldeani 125
Satiman 126
Lemagurut 126
Ogol 126
Implications for Laetoli Deposits and NVHC 127
Conclusions 129
References 129
Chapter 6: Geochemistry and Mineralogy of Laetoli Area Tuffs: Lower Laetolil through Naibadad Beds 132
Introduction 132
Background 133
Samples and Sample Sites 133
Methods 136
Results 136
Discussion 136
Lower Laetolil Tuffs 136
Upper Laetolil Tuffs 146
Upper Laetolil Yellow Marker Tuff and the Ndolanya Beds 147
Naibadad Beds 149
Tuff Alteration 149
Regional Correlations 151
Conclusions 151
References 152
Chapter 7: Geochemical and Mineralogic Characterization of Middle Stone Age Tools of Laetoli, Tanzania, and Comparisons with Possible SourceMaterials 153
Introduction 153
Methods 155
Results 156
Petrographic Characteristics 156
Geochemical Discrimination 157
Major Element Compositions 158
Trace Element Compositions 158
Nd and Sr Isotopic Compositions of Ogol and Lemagurut Lavas 158
Discussion 162
Comparison of Laetoli Artifacts and Local Lava Sources (Ogol Lavas) 162
Comparisons with Regional Volcanic Sources 170
Raw Material Acquisition 171
Limitations and Future Work 173
Conclusions 174
References 174
Chapter 8: The Ecology and Biogeography of the Endulen-Laetoli Area in Northern Tanzania 176
Introduction 176
Methods 177
The Serengeti Ecosystem and Laetoli 178
Climate 179
Topography 179
Soil 180
The Laetoli Woodlands 181
Vegetation Unit 1 – Montane Forest, Tall, Dense, Evergreen 181
Vegetation Unit 2 – Deciduous Woodland 181
Vegetation Unit 3 – Dense Riverine Bushland 183
Vegetation Unit 4 – Riverine Woodland and Gallery Forest 184
Vegetation Unit 5 – Escarpment Woodland, Forest Edge 186
Vegetation Unit 6 – Acacia Drepanolobium Woodland 187
Vegetation Unit 7 – Grassland 188
Disturbance 188
Distribution of the Laetoli Woodlands 189
Discussion 189
Woodland Drainage Catena 193
Riverine Catena 193
Altitude Catena 193
Potential Effects of Climate Change 193
Conclusions 195
References 208
Chapter 9: Phytoliths and Pollen, the Microscopic Plant Remains in Pliocene Volcanic Sediments Around Laetoli, Tanzania 210
Introduction 210
Materials and Methods 211
Pollen 211
Phytoliths 211
Application of Modern Phytolith Distribution 212
Results 215
Pollen 215
Lower Laetolil Beds (Kakesio and Noiti) 217
Upper Laetolil Beds 217
Upper Ndolanya Beds 218
Phytoliths 218
Lower Laetolil Beds (Kakesio and Noiti) 218
Upper Laetolil Beds 218
Upper Ndolanya Beds 218
Interpretation of the Phytoliths 218
Discussion 220
References 222
Chapter 10: Fossil Woods 225
Introduction 225
Locality and Age 225
Preservation and Taphonomy 226
Paleoenvironmental Approach and Interpretation 226
Materials and Methods 228
Diversity of Fossil Woods 231
Anatomical Descriptions of the Better Preserved Woods 231
Type A 231
Comparison and Identification 231
Type B 231
Comparison and Identification 232
Type C 232
Comparison and Identification 232
Type D 232
Comparison and Identification 234
Type E 234
Comparison and Identification 234
Type F 236
Comparison and Identification 236
Type G 236
Comparison and Identification 236
Type H 238
Comparison and Identification 238
Type I 238
Comparison and Identification 238
Vulnerability Index 238
Discussion 239
References 240
Chapter 11: Fossil Leaves, Fruits and Seeds 242
Introduction 242
Locality and Geology 242
Fossil Flora 242
Materials and Methods 243
Preservation 243
Morphotypes/Identification 243
Description and Identification of Macrofossils 243
Dicot Leaves 243
Description 245
Identification 245
Description 246
Description 246
Identification 247
Description 247
Identification 247
Description 247
Description 247
Description 247
Description 248
Description 248
Description 248
Monocot Leaves 248
Description 248
Seeds and Fruit 248
Description 248
Identification 248
Description 249
Identification 250
Description 250
Identification 250
Description 250
Description 250
Identification 250
Description 250
Description 251
Description 251
Identification 252
Description 252
Identification 252
Description 252
Identification 252
Description 252
Description 252
Description 252
Thorns and Spines 253
Description 253
Description 254
Identification 254
Monocot Rhizome 255
Description 255
Assorted Seeds from Early Collections 255
Discussion 256
East African Plant Record 256
Laetoli Leaves 256
Reproductive Structures 256
Thorns and Spines 257
Monocot Rhizome 257
Paleoecology 257
Conclusion 257
References 258
Chapter 12: Serengeti Micromammal Communities and the Paleoecology of Laetoli, Tanzania 260
Introduction 260
The Serengeti Ecosystem 262
Methods 263
Results 264
Discussion 265
Conclusions 268
References 268
Chapter 13: The Taphonomy and Paleoenvironmental Implications of the Laetoli Micromammals 271
Introduction 271
Material and Methods 272
Taphonomy 272
Surface Modification 273
Discussion 276
Paleoenvironment 281
Conclusions 282
References 283
Chapter 14: Coprolites: Taphonomic and Paleoecological Implications 285
Introduction 285
Carnivore Coprolites 285
Description of Specimens 287
EP 068/98 (Kakesio 4, Lower Laetolil Beds) 287
EP 1014/00 (Loc. 18, Upper Ndolanya Beds) 287
EP 1372/00 (Loc. 6, Upper Laetolil Beds, between Tuffs 5 and 6) 288
EP 2127/00 (Loc. 13, Upper Laetolil Beds, between Tuffs 6 and 7) 288
EP 4181/00 (Loc. 8, Upper Laetolil Beds, between Tuffs 5 and 7) 288
EP 813/03 (Loc. 9, Upper Laetolil Beds, between Tuffs 5 and 7) 289
EP 1246/03 (Loc. 7E, Upper Ndolanya Beds) 289
EP 2343/03 (Loc. 13, Upper Laetolil Beds, between Tuffs 6 and 7) 289
EP 599/04 (Loc. 10, Upper Laetolil Beds, below Tuff 2) 289
EP 786/04 (Loc. 7, Upper Laetolil Beds, between Tuffs 5 and 7) 290
EP 998/04 (Loc. 9, Upper Laetolil Beds, between Tuffs 5 and 7) 290
EP 1077/04 (Loc. 11, Upper Laetolil Beds, between Tuffs 7 and 8) 290
EP 1078/04 (Loc. 11, Upper Laetolil Beds, between Tuffs 7 and 8) 290
EP 1138/04 (Loc. 13, Upper Laetolil Beds, between Tuffs 6 and 8) 290
Discussion 290
Ruminant Coprolites 291
Description of Specimens 292
Type A 292
Type B 293
Type C 293
Type D 295
Other Bovid Coprolites 296
Discussion 296
Conclusions 296
References 297
Chapter 15: Stable Isotopic Analyses of Laetoli Fossil Herbivores 299
Introduction 299
Methods 301
Mammalian Tooth Enamel 301
Ostrich Eggshell (OES) 310
Sample Preparation for Isotopic Analyses of Inorganic Calcite Matrix of Ostrich Eggshells 310
Sample Preparation for Isotopic Analyses of Organic Residue within Eggshells 311
Results and Discussion 311
Mammalian Herbivore Enamel 311
d13Cenamel Overview 311
d18Oenamel Overview/Aridity Index 315
Isotopic Interpretations of Mammalian Enamel 318
Proboscidea 318
Rhinocerotidae 321
Suidae 321
Giraffidae 321
Equidae 322
Bovidae 322
Cercopithecidae 323
Carnivora 324
Ostrich Eggshell (OES) Analyses 324
d13COES and Diet 324
d18OOES and Aridity/Temperature 328
d15NOES and Rainfall 328
Isotopic Interpretations of Ostrich Eggshells 330
Conclusions 330
References 331
Chapter 16: Feeding Ecology and Niche Partitioning of the Laetoli Ungulate Faunas 335
Introduction 335
Materials 338
Methods 342
Data Analysis and Statistics 343
Cluster statistics 343
Mesowear scores 343
Results and Interpretations 343
Lineage Based Analysis of Mesowear Scores 346
Bovidae 346
Alcelaphini 346
Antilopini 346
Bovini 347
Cephalophini 348
Hippotragini 348
Neotragini 349
Tragelaphini 349
Giraffidae 350
Equidae 351
The Laetoli Ungulate Community Structure 351
Ecological and Environmental Trendsin the Laetoli Succession 351
The Upper Laetolil Beds Environmentand Its Transitions 351
The ULB-UNB Transition and the Upper Ndolanya Beds Paleoenvironment 355
Conclusions 356
References 357
Chapter 17: Paleoenvironments of Laetoli, Tanzania as Determined by Antelope Habitat Preferences 361
Introduction 361
Ecomorphology? 362
Why Antelopes? 362
Materials and Methods 362
Extant Antelopes 362
Fossils 365
Results 367
Habitat Preference 367
Body Size 368
Discussion 369
Appendix: Measurements and Ratios Used in This Study 370
Distal Radius 370
Astragalus 371
Proximal Phalanges 371
Intermediate Phalanges 371
Distal Phalanges 371
References 372
Chapter 18: Environmental Change within the Laetoli Fossiliferous Sequence: Vegetation Catenas and Bovid Ecomorphology 373
Introduction 373
Methods 374
Ecomorphological Analysis 374
The Fossil Sample 375
Habitats and Vegetation Associations 375
Rationale for the Habitat Classification 375
Present Habitats 377
Results of Ecomorphology Related to the Modern Laetoli Catenas 378
Ecomorphological Proportions within the Laetoli Succession 379
Faunal Differences in the Laetoli Sequence 381
The Laetolil-Ndolanya Transition 381
Environmental Change within the Upper Laetolil Beds 382
Laetoli Hominins 383
References 384
Chapter 19: Large Mammal Evidence for the Paleoenvironment of the Upper Laetolil and Upper Ndolanya Beds of Laetoli, Tanzania 387
Introduction 387
Materials and Methods 387
Community Structure 387
Indicator Species and Their Relative Abundance 388
Results and Discussion 389
Community Structure 389
Indicator Species and Their Relative Abundances 391
Paleoenvironmental Implications 394
Summary 395
References 396
Index 399