PALEOMAGNETISM PALEOMAGNETISM This is Volume 73 in the INTERNATIONAL GEOPHYSICS SERIES A series of monographs and textbooks Edited by RENATA DMOWSKA, JAMES R HOLTON, and H THOMAS ROSSBY A complete list of books in this series appears at the end of this volume PALEOMAGNETISM Continents and Oceans MICHAEL W.McELHINNY Gondwana Consultants Hat Head, New South Wales, 2440 Australia PHILLIP L McFADDEN Australian Geological Survey Organisation Canberra, 2601 Australia ACADEMIC PRESS A Harcourt Science and Technology Company San Diego San Francisco N e w York Boston London Sydney Tokyo Front cover photograph: A depiction of a dipole field Courtesy of Michael W McElhinny and Phillip L McFadden Back cover photograph: Global paleogeographic map for Late Permian (See Figure 7.11 for more details.) This book is printed on acid-free paper Copyright © 2000 by ACADEMIC PRESS All Rights Reserved No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the pubUsher Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt, Inc., 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Academic Press A Harcourt Science and Technology Company 525 B Street, Suite 1900, San Diego, California 92101-4495, U.S.A http \ll^^^ apnet com Academic Press 24-28 Oval Road, London NWl 7DX, UK http://www.hbuk.co.uk/ap/ Harcourt/Academic Press A Harcourt Science and Technology Company 200 Wheeler Road, Burhngton, Massachusetts 01803 http://www.harcourt-ap.com Library of Congress Catalog Card Number: 99-65104 International Standard Book Number: 0-12-483355-1 International Standard Serial Number: 0074-6142 PRINTED IN THE UNITED STATES OF AMERICA 99 00 01 02 03 04 MM Contents Preface xi Chapter Geomagnetism and Paleomagnetism 1.1 Geomagnetism 1.1.1 Historical 1.1.2 Main Features of the Geomagnetic Field 1.1.3 Origin of the Main Field 1.1.4 Variations of the Dipole Field with Time 1 12 1.2 Paleomagnetism 1.2.1 Early Work in Paleomagnetism 1.2.2 Magnetism in Rocks 1.2.3 Geocentric Axial Dipole Hypothesis 1.2.4 Archeomagnetism 1.2.5 Paleointensity over Geological Times 1.2.6 Paleosecular Variation 14 14 16 18 22 25 26 Chapter Rock Magnetism 2.1 Basic Principles of Magnetism 2.1.1 Magnetic Fields, Remanent and Induced Magnetism 2.1.2 Diamagnetism and Paramagnetism 2.1.3 Ferro-, Antiferro-, and Ferrimagnetism 2.1.4 Hysteresis 31 31 34 35 37 2.2 Magnetic Minerals in Rocks 2.2.1 Mineralogy 2.2.2 Titanomagnetites 2.2.3 Titanohematites 38 38 40 45 vi Contents 2.2.4 Iron Sulfides and Oxyhydroxides 2.3 Physical Theory of Rock Magnetism 2.3.1 Magnetic Domains 2.3.2 Theory for Single-Domain Grains 2.3.3 Magnetic Viscosity 2.3.4 Critical Size for Single-Domain Grains 2.3.5 Thermoremanent Magnetization 2.3.6 Crystallization (or Chemical) Remanent Magnetization 2.3.7 Detrital and Post-Depositional Remanent Magnetization 2.3.8 Viscous and Thermo viscous Remanent Magnetization 2.3.9 Stress Effects and Anisotropy 46 48 48 51 54 56 60 64 68 71 74 Chapter Methods and Techniques 3.1 Sampling and Measurement 3.1.1 Sample Collection in the Field 3.1.2 Sample Measurement 79 79 82 3.2 Statistical Methods 3.2.1 Some Statistical Concepts 3.2.2 The Fisher Distribution 3.2.3 Statistical Tests 3.2.4 Calculating Paleomagnetic Poles and Their Errors 3.2.5 Other Statistical Distributions 84 84 87 91 98 99 3.3 Field Tests for Stability 3.3.1 Constraining the Age of Magnetization 3.3.2 The Fold Test 3.3.3 Conglomerate Test 3.3.4 Baked Contact Test 3.3.5 Unconformity Test 3.3.6 Consistency and Reversals Tests 100 100 101 108 109 111 112 3.4 Laboratory Methods and Applications 3.4.1 Progressive Stepwise Demagnetization 3.4.2 Presentation of Demagnetization Data 3.4.3 Principal Component Analysis 3.4.4 Analysis of Remagnetization Circles 114 114 119 124 125 3.5 Identification of Magnetic Minerals and Grain Sizes 3.5.1 Curie Temperatures 3.5.2 Isothermal Remanent Magnetization 3.5.3 The Lowrie-Fuller Test 3.5.4 Hysteresis and Magnetic Grain Sizes 127 127 128 131 133 Contents 3.5.5 Low-Temperature Measurements vii 13 Chapter Magnetic Field Reversals 4.1 Evidence for Field Reversal 4.1.1 Background and Definition 4.1.2 Self-Reversal in Rocks 4.1.3 Evidence for Field Reversal 137 137 139 141 4.2 The Geomagnetic Polarity Time Scale 4.2.1 Polarity Dating of Lava Flows 0-6 Ma 4.2.2 Geochronometry of Ocean Sediment Cores 4.2.3 Extending the GPTS to 160 Ma 143 143 146 149 4.3 Magnetostratigraphy 4.3.1 Terminology in Magnetostratigraphy 4.3.2 Methods in Magnetostratigraphy 4.3.3 Quality Criteria for Magnetostratigraphy 4.3.4 Late Cretaceous-Eocene: The Gubbio Section 4.3.5 Late Triassic GPTS 4.3.6 Superchrons 154 154 15 157 158 159 162 4.4 Polarity Transitions 4.4.1 Recording Polarity Transitions 4.4.2 Directional Changes 4.4.3 Intensity Changes 4.4.4 Polarity Transition Duration 4.4.5 Geomagnetic Excursions 164 164 166 171 172 174 4.5 Analysis of Reversal Sequences 4.5.1 Probability Distributions 4.5.2 Filtering of the Record 4.5.3 Nonstationarity in Reversal Rate 4.5.4 Polarity Symmetry and Superchrons 175 175 177 179 180 Chapter Oceanic Paleomagnetism 5.1 Marine Magnetic Anomalies 5.1.1 Sea-Floor Spreading and Plate Tectonics 5.1.2 Vine-Matthews Crustal Model 5.1.3 Measurement of Marine Magnetic Anomalies 5.1.4 Nature of the Magnetic Anomaly Source 183 183 188 189 191 5.2 Modeling Marine Magnetic Anomalies 5.2.1 Factors Affecting the Shape of AnomaHes 195 195 viii Contents 5.2.2 Calculating Magnetic Anomalies 199 5.3 Analyzing Older Magnetic Anomalies 5.3.1 The Global Magnetic Anomaly Pattern 5.3.2 Magnetic Anomaly Nomenclature 5.3.3 The Cretaceous and Jurassic Quiet Zones 204 204 208 209 5.4 Paleomagnetic Poles for Oceanic Plates 5.4.1 Skewness of Magnetic Anomalies 5.4.2 Magnetization of Seamounts 5.4.3 Calculating Mean Pole Positions from Oceanic Data 212 212 214 216 5.5 Evolution of Oceanic Plates 5.5.1 The Hotspot Reference Frame 5.5.2 Evolution of the Pacific Plate 221 221 224 Chapter Continental Paleomagnetism 6.1 Analyzing Continental Data 227 6.2 Data Selection and Reliability Criteria 6.2.1 Selecting Data for Paleomagnetic Analysis 6.2.2 Reliability Criteria 6.2.3 The Global Paleomagnetic Database 228 228 228 230 6.3 Testing the Geocentric Axial Dipole Model 6.3.1 The Past Million Years 6.3.2 The Past 3000 Million Years 6.3.3 Global Paleointensity Variations 6.3.4 Paleoclimates and Paleolatitudes 232 232 236 239 241 6.4 Apparent Polar Wander 6.4.1 The Concept of Apparent Polar Wander 6.4.2 Determining Apparent Polar Wander Paths 6.4.3 Magnetic Blocking Temperatures and Isotopic Ages 245 245 246 249 6.5 Phanerozoic APWPs for the Major Blocks 6.5.1 Selection and Grouping of Data 6.5.2 North America and Europe 6.5.3 Asia 6.5.4 The Gondwana Continents 251 251 252 261 269 Chapter Paleomagnetism and Plate Tectonics 7.1 Plate Motions and Paleomagnetic Poles 7.1.1 Combining Euler and Paleomagnetic Poles 281 281 Contents 7.1.2 Making Reconstructions from Paleomagnetism \\ 287 7.2 Phanerozoic Supercontinents 7.2.1 Laurussia 7.2.2 Paleo-Asia 7.2.3 Gondwana 7.2.4 Pangea 7.2.5 Paleogeography: 300 Ma to the present 289 289 291 295 298 301 7.3 Displaced Terranes 7.3.1 Western North America 7.3.2 The East and West Avalon Terranes 7.3.3 Armorica 7.3.4 The Western Mediterranean 7.3.5 South and East Asia 303 303 306 308 310 312 7.4 Rodinia and the Precambrian 7.4.1 Rodinia 7.4.2 Paleomagnetism and Rodinia 7.4.3 Earth History: Ma to the Present 7.4.4 Precambrian Cratons 315 315 317 321 323 7.5 Non-Plate Tectonic Hypotheses 7.5.1 True Polar Wander 7.5.2 An Expanding Earth? 325 325 330 References 333 Index 311 380 reversals, 15 susceptibility (x), 33-35, 37-38, 53-54 susceptibility anisotropy, 75-77 variation - see declination viscosity, 54-56 Magnetite, ^ Magnetocrystalline anisotropy, 51-53, 135 Magnetoelastic energy, 51 Magnetostatic energy, 48-51 Magnetostratigraphy, 154-164 Gubbio section, 158-159 Late Carboniferous-Permian, 162-164 methods, 155-167 Newark Basin, 159-161, 181 quality criteria, 157 terminology, 154-155 Magnetostriction, 51-53 Magnetostrictive strain energy, 51 Mammoth subchron, 146 Marie Byrd Land, 275, 279 Marine magnetic anomalies, 15,188 antisymmetric, 199 calculations, 199-203 measurement of, 189-191 nomenclature, 205-209 quiet zones, 209-212 reduction to pole, 196-197 relative amplitude factor, 200-201, 213, 217-220 shape, 195-199 skewness, 200-203 symmetric, 199 variation with latitude, 196-197 Matuyama chron, 144-146 Mean direction, calculation of, 89-90 comparisons of, 93-94 Mean lithosphere framework, 326-327 Mesosphere, 185 Mesozoic dipole low, 25-26, 211-212 Microscopic coercivity, 52-55 Midland craton, 256-257 Mongolia, 261 Morin transition, 45, 135 Multidomain (MD) grains, 50, 56-60, 62-63, 133-136 Lowrie-FuUer test, 131-133 Natural remanent magnetization (NRM), 14-17 Navier-Stokes equation, 11 Neckham,Alexander, N6el temperature, 37 Newark Basin section, 159-161, 181 Index Nondipole field, 6-7, 24 Nonzonal harmonics, Normal (gaussian) distribution, 84-87 Norman, Robert, North Australia craton, 275-276 North Britain terrane, 256-261, 269, 289-291, 321-322 APWP, 258-261 North China, 261-262, 265-267, 291-296, 301-302,324 APWP, 265-267 North magnetic pole, 4-5 Null hypothesis, 87 Nunivak subchron, 146 Ocean crust model, 191-192 Offset-dipole model, 234-235 Olduvai subchron, 144-146 Omega (co) effect, 11-12 Omolon terrane, 262, 314-315 Oxidation of magnetic minerals, and polarity, 141 high temperature, 42-45, 127-128 low temperature, ^ , 127-128, 192-193 Pacific plate APWP, 219-220 evolution, 224-226 Paleoclimates and paleolatitudes, 21-22, 231245 coal deposits, 243-244 evaporites, 242-243 organic reefs, 242 phosphate deposits, 244-245 Paleointensity, 21, 24-26, 239-241 Mesozoic dipole low, 25-26, 211-212 Paleomagnetic Euler pole, 248 latitude, 19 Paleomagnetic poles, 20-22 combined with Euler poles, 281-286 errors in, 98-99 from oceanic plates, 216-227 Paleomeridian method, 329-332 Paleosecular variation, 26-29 from lavas (PSVL), 28-29 Pangea, 298-301, 323-324 Pannotia, 321-324 Paramagnetism, 34, 55 Partial thermoremanent magnetization (PTRM), 61 Peninsular terrane, 252-253, 303-305 Index Peregrinus, Petrus, 1-2 Phoenix plate, 225-226 Pilbara craton, 275-276 Piston cores, 81 Plate tectonics, 183-188 velocity (minimum), 286-287 Poisson distribution (polarity intervals), 177178, 181 Polarity bias, 145, 180-182 Polarity intervals, distribution, 177-178 lengths, 162-164 Polarity transitions, directional changes, 166-171 duration, 172-174 intensity changes, 171-172 preferred paths, 157-171 Poloidal magnetic field, 10-12 Post-depositional remanent magnetization (PDRM), 16-17,70-71 Precision parameter comparison of, 92-93 definition, 87-90 Primary magnetization, 17 Principal component analysis, 124-125 Pseudobrookite, 38-46 Pseudo-single-domain (PSD) grains, 56-60, 133-135 Pyrrhotite, 40, 46-47, 130-131 Qiangtang terrane, 262, 275, 279, 313-314 Random directions, conglomerate test, 108-109 test for, 94 Reconstructions from paleomagnetism, 287288 Redbeds, CRM, 66 Relaxation time, 54-56, 59-60, 72-74 Reliability criteria, 227-230 Remagnetization circles, 125-126 Reunion subchron, 144-146 Reversal sequences, analysis, 175-182 filtering of record, 177-178 probability distribution, 175-177 Reversals of the geomagnetic field, definition, 137-139 evidence for, 141-143 381 Reversals test, 112-114 Rheic Ocean, 301, 323-324 Right-handed effect, 234 Rio de la Plata craton, 269, 273, 322-324 Rodinia, 315-325 Rotational remanent magnetization (RRM), 115 Sample collection, 79-81 definition, 80 measurement, 82-84 Sao Francisco craton, 269, 273, 322-324 Saturation magnetization, 37-38 remanence, 37-38 Sea-floor spreading, 183-185 equatorial rate, 187-188 half-rate, 183 map, 207 rate, 183-187 Seamount magnetization, 214-216, 218-219 Secondary magnetizafion, 17, 25 Secular variadon 5-6, 14, 26-29 Self-reversal of magnetization, 139-141 Shape anisotropy, 49, 52-53 Siberia, 261-265, 291-292, 301-302, 316, 320, 322-324 Aldan block, 262-263 Anabar block, 262-263 APWP, 263-265 Sidufjall subchron, 144, 146 Sikhote Alin terrane, 261-262, 314-315 Single-domain (SD) grains, 50-60, 133-136 critical size, 56-60 Lowrie-Fuller test, 131-133 Site, definition of, 79-80 Skewness (of magnefic anomalies), 200-203, 212-214 anomalous skewness, 202-203, 212-214 South America APWP, 273-275 South China, 261-262, 267-268, 291-296, 301-302,316,324 APWP, 265-268 South magnetic pole, 4-5 Spherical harmonics, 6-9, 12-14 Spontaneous magnefization, 35-37 Standard deviafion, 85, 90 error of the mean, 86 Sfikine terrane, 252-253 Stress induced anisotropy, 52-53, 74-77 Subchron, definition, 154 382 Superchron, 154, 162-164, 179-182 Cretaceous Normal, 152, 163-164, 179182,209-210 Kiaman Reverse, 162-164 Superparamagnetism, 55, 59-60 Susceptibility (x) - see magnetic susceptibility, initial susceptibility Sveconorwegian loop, 320 SWEAT connection, 315 Symmetric families, 12 Synfolding magnetization, 107-108 Tarim, 261-262, 267-268, 291-293, 324 APWP, 267-268 Tasman Fold Beit, 275-277 Terrane trajectories, 305-306 Tethys Ocean, 301-302, 324 Thermal demagnetization, 117-118 Thermoremanent magnetization (TRM), 16-17, 60-64 Thermoviscous remanent magnetization (TVRM), 71-74 Thurston Island-Eights Coast terrane, 275, 279 Thvera subchron, 146 Time-averaged paleomagnetic field, 18 Titanohematite, 38-45 Titanomaghemite, 38-45, 192-193 Titanomagnetite, 38-45, 108, 192-193 Toroidal magnetic field, 10-12 True polar wander (TPW), 297, 325-330 Index U-channels, 81,84 Ulv5spinel, 38-45 Unconformity test, 111- 112 Variance, 85 Velocity field, 10 Verwey transition, ^ , 135-136 Vine-Matthews crustal model, 188-189 Virtual dipole moment (VDM), 24-29 Virtual geomagnetic pole (VGP), 21-24 Viscous partial thermoremanent magnetization (VPTRM) - see thermoviscous remanent magnetization (TVRM) Viscous remanent magnetization (VRM), 17, 71-74 West Africa craton, 269, 316, 322-324 West Avalon terrane, 252-253, 306-310, 322324 Westward drift, 6-7, 13-14 Wrangell terrane, 252-253, 303-305 Yilgam craton, 275 Zijderveld diagram, 119-123 Zonal harmonics, 9, 235 International Geophysics Series EDITED BY RENATADMOWSKA Division of Engineering and Applied Science Harvard University Cambridge, Massachusetts JAMES R HOLTON Department of Atmospheric Sciences University of Washington Seattle, Washington H THOMAS ROSSBY Graduate School of Oceanography University of Rhode Island Narragansett, Rhode Island Volume BENO GUTENBERG Physics of the Earth's Interior 1959* Volume JOSEPH W CHAMBERLAIN Physics of the 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Paleoseismology 1996 Volume 63 RONALD T MERRILL, MICHAEL W MCELHINNY, AND PHILLIP L MCFADDEN The Magnetic Field of the Earth: Paleomagnetism, the Core, and the Deep Mantle 1996 386 International Geophysics Series Volume 64 NEIL D OPDYKE and JAMES CHANNELL Magnetic Stratigraphy 1996 Volume 65 JUDITH A CURRY and PETER J WEBSTER Thermodynamics of Atmospheres and Oceans 1998 Volume 66 LAKSHMI H KANTHA and CAROL ANNE CLAYSON Numerical Models of Oceans and Oceanic Processes Volume 67 LAKSHMI H KANTHA and CAROL ANNE CLAYSON Small Scale Processes in Geophysical Fluid Flows Volume 68 RAYMOND S BRADLEY Paleoclimatology, Second Edition 1999 Volume 69 LEE-LUENG FU and ANNY CAZANAVE Satellite Altimetry Volume 70 DAVID A RANDALL General Circulation Model Development Volume 71 PETER WARNECK Chemistry of the Natural Atmosphere, Second Edition Volume 72 M C JACOBSON, R J CHARLESON, H RODHE, and G H ORIANS Earth System Science: From Biogeochemical Cycles to Global Change Volume 73 MICHAEL W MCELHINNY and PHILLIP L MCFADDEN Paleomagnetism: Continents and Oceans 1999 m cs m ^^ ^ 1• (TV s f< VO • '^ • '"* ^ ^ 1•m (^.^ O •^ •I• ON ""^ otaH • ,-^ ^ 3; I1 t^ CM ^ 11 ^ Id ^ [ o o M- E ir> B li B m M V*i^ o tn W) CO sa & o g •* ^cd *n f^- 20S HOE 180E MOW lOOW 60W HOE 180E HOW lOOW 60W 140E 180E HOW lOOW 60W 1401 1801 MOW lOOW 60W 60N 40N 20N 20S 60N 40\ 20N 20S 60N 40N 20N 20S (a) Penman 255 Ma ,s.»^' PANTHALASSK OCEAN iNGEA PALI () l i n n s ^