Neoproterozoic-Cambrian Tectonics, Global Change and Evolution (eBook)

Front cover 1
Neoproterozoic-Cambrian Tectonics, Global Change and Evolution: A Focus on South Western Gondwana 4
Copyright page 5
Contents 6
Contributors 12
Preface 16
Acknowledgements 17
Section I: Introduction 18
Part I: Introduction 18
Chapter 1. The Neoproterozoic and Cambrian: A Time of Upheavals, Extremes and Innovations 20
1.1. The Neoproterozoic World 20
1.2. Tectonic Upheaval and Geodynamic Twists: The Tale of Two Supercontinents 20
1.3. The Ocean and Atmosphere: Oxygenation and Anomalies 22
1.4. Climatic Extremes and Conundrums 24
1.5. Permissive Ecology and Neoproterozoic-Cambrian Climate 26
1.6. Emergence of Metazoa: A New World Order 27
1.7. Conclusions 28
Section II: Neoproterozoic-cambrian events in SW Gondwana 30
Part 2: Neoproterozoic-Cambrian Evolution of theAmazonian Palaeocontinent 30
Chapter 2. The Amazonian Palaeocontinent 32
2.1. Introduction 32
2.2. Lithostratigraphy 34
2.3. Chemostratigraphy 40
2.4. Geochronological Constraints 42
2.5. Palaeomagnetic Constraints 44
2.6. Conclusions and Regional Analysis 44
Acknowledgements 45
Part 3: Neoproterozoic-Cambrian Evolution of the São Francisco Palaeocontinent 46
Chapter 3. The São Francisco Palaeocontinent 48
3.1. Introduction 48
3.2. Synthesis of the Lithostratigraphic Units 49
3.3. Isotope Chemostratigraphy 77
3.4. Geochronology and Provenance: Synthesis of U-Pb and Sm-Nd Data 81
3.5. Synthesis of Neoproterozoic Mineralisations: Lead, Zinc, Fluorine, Barium and Phosphates 83
3.6. Conclusions and Regional Analysis 84
Acknowledgements 86
Part 4: Neoproterozoic-Cambrian Evolution of the Rio de La Plata Palaeocontinent 88
Chapter 4.1. Extension and General Evolution of the Río de la Plata Craton 90
Chapter 4.2. Lithostratigraphy 104
4.2.1. Introduction 104
4.2.2. Tandilia System, Argentina 104
4.2.3. Nico Pérez Terrane, Uruguay 109
4.2.4. Piedras de Afilar Formation 116
Acknowledgements 118
Chapter 4.3. Biostratigraphy 120
4.3.1. Introduction 120
4.3.2. Tonian and Cryogenian Fossil Record 120
4.3.3. Ediacaran Fossil Record 122
4.3.4. Cambrian Fossil Record 129
4.3.5. Biostratigraphic Correlations and Discussion 130
Acknowledgements 131
Chapter 4.4. Chemostratigraphy 132
4.4.1. Introduction 132
4.4.2. Carbon-Isotope Chemostratigraphy 132
4.4.3. Strontium-Isotope Chemostratigraphy 137
4.4.4. Synthesis 138
Acknowledgements 139
Chapter 4.5. Palaeoclimatic Events 140
4.5.1. Palaeoclimatic Evolution of the Río de la Plata Palaeocontinent in the Neoproterozoic-Cambrian 140
4.5.2. Diamictites of the Las Ventanas and Playa Hermosa Formations 141
4.5.3. Diamictites in Tandilia 143
4.5.4. Other Units 143
4.5.5. Indirect Evidence of Late Ediacaran Glaciation 144
4.5.6. Record of Cambrian Global Warming 146
4.5.7. Discussion and Summary 146
Acknowledgements 147
Chapter 4.6. Palaeogeography 148
4.6.1. Río de la Plata Craton: A Part of Rodinia 148
4.6.2. Latest Cryogenian-Early Ediacaran Rifting 150
4.6.3. Ediacaran Drift Phase and Passive Margin 153
4.6.4. Evolution of the Western Boundary of the Río de la Plata Palaeocontinent 154
4.6.5. Lower Cambrian Búzios Orogeny 156
4.6.6. Cambrian Anorogenic Magmatism 157
4.6.7. Palaeomagnetic Constraints 158
4.6.8. Conclusions 158
Acknowledgements 158
4.1. Introduction 90
4.12. Main Outcrop Areas 92
4.13. Conclusions 100
Acknowledgements 102
Part 5: Neoproterozoic to Early Palaeozoic Evolution of Southwestern Africa 160
Chapter 5.1. guration of Pan-African Orogenic Belts in Southwestern Africa 162
Chapter 5.2. Continental Rifting 170
5.2.1. Introduction 170
5.2.2. Pre-Rift Magmatism 170
5.2.3. Rift Sedimentation 172
5.2.4. Syn-Rift Magmatism 174
Acknowledgements 176
Chapter 5.3. Passive Continental Margin Evolution 178
5.3.1. Introduction 178
5.3.2. Spreading-Phase Sedimentary Successions in the Damara Orogen 179
5.3.3. Post-Rift Evolution in the Gariep Belt 193
5.3.4. Relics of Oceanic Crust 195
Acknowledgements 198
Chapter 5.4. Syn- to Late-Orogenic Sedimentary Basins of Southwestern Africa 200
5.4.1. Introduction 200
5.4.2. Stratigraphy and Depositional Environment 201
Acknowledgements 220
Chapter 5.5. Orogenic Tectono-Thermal Evolution 222
5.5.1. The Kaoko Belt 222
5.5.2. The Damara Belt 229
5.5.3. The Gariep Belt 233
5.5.4. The Saldania Belt 235
Acknowledgements 235
Chapter 5.6. Syn- to Post-Orogenic Magmatism 236
5.6.1. Plutonic Rocks in the Kaoko Belt 236
5.6.2. Plutonic Rocks in the Damara Belt 237
5.6.3. Post-Orogenic Plutonism in the Gariep Belt 241
5.6.4. Plutonism in the Saldania Belt 241
Acknowledgements 243
Chapter 5.7. Mineral Deposits 244
5.7.1. Introduction 244
5.7.2. Rifting- and Spreading-Phase Deposits 244
5.7.3. Syn- and Post-Tectonic Deposits 245
Acknowledgements 246
5.8. Geodynamic Synthesis of the Damara Orogen Sensu Lato 248
Acknowledgements 252
Part 6: Neoproterozoic-Cambrian Evolution of The Pampean Orogen 254
Chapter 6. The Pampean Orogen: Ediacaran-Lower Cambrian Evolutionary History of Central and Northwest Region of Argentina 256
6.1. Introduction 256
6.2. Geological Setting 257
6.3. Interpretation of the Regional Outline 257
6.4. The Puncoviscana Basin 260
6.5. Tilcarian Orogeny 268
6.6. Plutonic Rocks 268
6.7. Conclusions 270
Acknowledgements 271
Part 7: Microcontinents and Suspect Terranes in SW Gondwana 272
Chapter 7.1. The Paranapanema Lithospheric Block: Its Nature and Role in the Accretion of Gondwana 274
7.1.1. Introduction 274
7.1.2. Support from Regional Geology and Geotectonics 275
7.1.3. Support from Gravity: Means and Methods 280
7.1.4. Magnetotellurics and Magnetometry 283
7.1.5. Seismic Data 284
7.1.6. Support from Geochemistry and Isotope Geology 284
7.1.7. The Paranapanema Block and Its Role in the Accretion of Gondwana 287
Acknowledgements 289
Chapter 7.2. The Evolution and Tectonic Setting of the Luis Alves Microplate of Southeastern Brazil: An Exotic Terrane during the Assembly of Western Gondwana 290
7.2.1. Introduction 290
7.2.2. Regional Geological Divisions 292
7.2.3. Basement Rocks of the Luís Alves Microplate 292
7.2.4. Neoproterozoic Units of the Luís Alves Microplate 293
7.2.5. The Age of the Luís Alves Microplate Basement 297
7.2.6. Interpretation and Discussion of Radiometric Results 300
7.2.7. Tectonic Implications 300
7.2.8. Conclusion 303
Acknowledgements 304
Section III: Synthesis and Global Implications 310
Part 8: Palaeogeographic Evolution from Rodinia to Gondwana 310
Chapter 8. Tectonic Events and Palaeogeographic Evolution of Southwestern Gondwana in the Neoproterozoic and Cambrian 312
8.1. Introduction 312
8.2. Ocean Basins and Corresponding Sedimentary Successions 313
8.3. Key Blocks in Southwestern Gondwana Amalgamation 315
8.4. Evidence of Westward Sequential Opening and Closure of Basins 319
8.5. Proposed Geodynamic Model and Possible Causes 328
8.6. Discussion and Environmental Consequences 332
Part 9: Neoproterozoic-Cambrian Biota 334
Chapter 9.1. Neoproterozoic Acritarch Evolution 336
9.1.1. Tonian to Early Cryogenian Diversification (gt1,000-700Ma) 336
9.1.2. Mid-Cryogenian Crisis (770-740Ma) 339
9.1.3. Mid-Cryogenian Recovery (ca. 740-700Ma) 339
9.1.4. Late Cryogenian Crisis (ca. 700-635Ma) 339
9.1.5. Early Ediacaran Recovery (635-ca. 580Ma) 340
9.1.6. Middle Ediacaran Explosive Diversification (ca. 580-560Ma) 340
9.1.7. Late Ediacaran Plankton Crisis (ca. 560-542Ma) 341
9.1.8. Cambrian Explosive Radiation (542-470Ma) 342
9.1.9. Discussion 342
9.1.10. Conclusions 342
Acknowledgements 343
Chapter 9.2. Skeletonised Metazoans and Protists 344
9.2.1. Introduction 344
9.2.2. Calcareous Skeletons 345
9.2.3. Siliceous Skeletons 349
9.2.4. Phosphatic Skeletons 350
9.2.5. Agglutinated Skeletons 351
9.2.6. Discussion and Conclusions 354
Acknowledgements 355
Chapter 9.3. Trace Fossils and the Agronomic Revolution at the Neoproterozoic-Cambrian Transition in Southwest Gondwana 356
9.3.1. Introduction 356
9.3.2. Trace Fossils in Northwest Argentina (South America) 357
9.3.3. Trace Fossils of the Nama Group 359
9.3.4. Trace Fossils of the Vanrhynsdorp Group (ca. 550-535Ma) 361
9.3.5. Conclusions 362
Acknowledgements 364
Part 10: Neoproterozoic-Cambrian Biogeochemical Evolution 366
Chapter 10. Neoproterozoic-Cambrian Biogeochemical Evolution 368
10.1. Introduction 368
10.2. Tectonics and Palaeoclimate 369
10.3. The Carbon Isotope Record 371
10.4. The Strontium Isotope Record 373
10.5. The Sulphur Isotope Record 374
10.6. Ediacaran-Cambrian Palaeobiology 376
10.7. Late Neoproterozoic-Cambrian Ocean Redox 379
10.8. Reorganisation of the Marine Carbon Cycle 381
10.9. Conclusions 382
Acknowledgements 382
Part 11: Neoproterozoic-Cambrian Palaeoclimatic Events 384
Chapter 11.1. Neoproterozoic to Cambrian Palaeoclimatic Events in Southwestern Gondwana 386
11.1.1. Constructing a Global Record of Neoproterozoic Palaeoclimatic Variations 386
11.1.2. Age Constraints for Cryogenian Glacial Deposits in Southwestern Gondwana 388
11.1.3. Chemostratigraphic Records of Palaeoclimatic Events in Southwestern Gondwana 390
11.1.4. A Synthesis of the Palaeoclimatic Puzzle from Southwestern Gondwana 400
11.1.5. Conclusions 405
Acknowledgements 405
Chapter 11.2. Neoproterozoic Glacial Events in Eurasia 406
11.2.1. Introduction 406
11.2.2. Middle Cryogenian Glaciations 406
11.2.3. Late Cryogenian Glaciations 409
11.2.4. Middle Ediacaran Glaciation 416
11.2.5. Late Ediacaran Glaciations 417
11.2.6. Discussion 419
11.2.7. Conclusions 420
Acknowledgments 420
References 422
Subject Index 472