Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information STRUCTURAL GEOLOGY An Introduction to Geometrical Techniques fourth edition Many textbooks describe information and theories about the Earth without training students to utilize real data to answer basic geological questions. This volume – a combi- nation of text and lab book – presents an entirely different approach to structural geology. Designed for undergraduate laboratory classes, it is dedicated to helping students solve many of the geometrical problems that arise from field observations. The basic approach is to supply step-by-step instructions to guide students through the methods, which include well-established techniques as well as more cutting-edge approaches. Particular emphasis is given to graphical methods and visualization techniques, intended to support students in tackling traditionally challenging two- and three-dimensional problems. Exer- cises at the end of each chapter provide students with practice in using the techniques, and demonstrate how observations and measurements from the field can be converted into useful information about geological structures and the processes responsible for creating them. Building on the success of previous editions, this fourth edition has been brought fully up-to-date and incorporates new material on stress, deformation, strain and flow. Also new to this edition are a chapter on the underlying mathematics and discussions of uncertainties associated with particular types of measurement. With stereonet plots and full solutions to the exercises available online at www.cambridge.org/ragan, this book is a key resource for undergraduate students as well as more advanced students and researchers wanting to improve their practical skills in structural geology. Don Ragan was educated at Occidental College, University of Southern California and at the University of Washington in Seattle, receiving his Ph.D. in 1960. He spent a year as a Fulbright Scholar at the University of Innsbruck, and later, with a National Sci- ence Foundation Fellowship, at Imperial College, London, where he received a Diploma of Membership in Geology (DIC). His teaching career at the University of Alaska, Fair- banks, and at Arizona State University has spanned a total of 34 years, and has focused on imbuing students with a thorough understanding of geometrical and analytical tech- niques in structural geology. His research interests center on the role of structural settings in structure-making processes, including studies of Alpine peridotites, glacial ice and welded tuffs. © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information STRUCTURAL GEOLOGY An Introduction to Geometrical Techniques fourth edition donal m. ragan Arizona State University, USA © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information cambridge university press Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao˜ Paulo, Delhi Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/ragan c D. M. Ragan 2009 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2009 Printed in the United Kingdom at the University Press, Cambridge A catalogue record for this publication is available from the British Library ISBN 978-0-521-89758-7 hardback ISBN 978-0-521-74583-3 paperback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information For Janne, Anneliese and Asta´ © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information Contents Preface page xv Acknowledgements xvii 1 Structural planes 1 1.1 Introduction 1 1.2 Definitions 1 1.3 Dip and strike 2 1.4 Accuracy of angle measurements 5 1.5 Graphic methods 10 1.6 Finding apparent dip 13 1.7 Analytical solutions 15 1.8 Cotangent method 17 1.9 True dip and strike 18 1.10 Dip vectors 20 1.11 Three-point problem 24 1.12 Observed apparent dips 25 1.13 Exercises 27 2 Thickness and depth 30 2.1 Definitions 30 2.2 Thickness determination 31 2.3 Thickness by direct measurement 31 2.4 Thickness from indirect measurements 32 2.5 Apparent thickness 36 2.6 Thickness between non-parallel planes 39 2.7 Thickness in drill holes 41 2.8 Depth to a plane 43 2.9 Distance to a plane 44 2.10 Error propagation 46 2.11 Exercises 54 vii © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information viii Contents 3 Lines and intersecting planes 57 3.1 Definitions 57 3.2 Linear structures 57 3.3 Plunge of a line 59 3.4 Pitch of a line 61 3.5 Intersecting planes 64 3.6 Cotangent method 65 3.7 Structure contours 66 3.8 Line vectors 67 3.9 Accuracy of trend determinations 69 3.10 Exercises 71 4 Planes and topography 72 4.1 Exposures on horizontal surfaces 72 4.2 Effect of topography 74 4.3 Dip and strike from a geological map 76 4.4 Linear interpolation 77 4.5 Parallel lines 79 4.6 Three-point problem 80 4.7 Structure contours 82 4.8 Predicting outcrop patterns 84 4.9 Exercises 87 5 Stereographic projection 88 5.1 Introduction 88 5.2 Stereogram 88 5.3 Stereonet 92 5.4 Plotting techniques 93 5.5 Measuring angles 99 5.6 Attitude problems 101 5.7 Polar net 104 5.8 Dip and strike errors 105 5.9 Intersection errors 106 5.10 Exercises 107 6 Rotations 109 6.1 Introduction 109 6.2 Basic techniques 109 6.3 Sequential rotations 114 6.4 Rotations about inclined axes 116 6.5 Rotational problems 118 6.6 Tilting problems 119 © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information Contents ix 6.7 Two tilts 121 6.8 Folding problems 122 6.9 Small circles 124 6.10 Exercises 128 7 Vectors 130 7.1 Introduction 130 7.2 Sum of vectors 134 7.3 Products of vectors 136 7.4 Circular distributions 143 7.5 Spherical distributions 147 7.6 Rotations 149 7.7 Rotational problems 154 7.8 Three-point problem 157 8 Faults 165 8.1 Definitions 165 8.2 Fault classification 166 8.3 Slip and separation 168 8.4 Faults in three dimensions 172 8.5 Slip and its determination 174 8.6 Overthrusts 179 8.7 Fault terminations 182 8.8 Faults and folds 184 8.9 Extension and contraction 185 8.10 Rotation 188 8.11 Facing on faults 194 8.12 Dilation of dikes 195 8.13 Exercises 197 9 Stress 198 9.1 Introduction 198 9.2 Traction 199 9.3 Stress components 201 9.4 Stress in two dimensions 204 9.5 Mohr Circle for stress 209 9.6 Superimposed stress states 215 9.7 Pole of the Mohr Circle 217 9.8 Role of pore pressure 222 9.9 Deviatoric and hydrostatic stress 223 9.10 Stress ellipse 224 © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M. Ragan Frontmatter More information x Contents 9.11 Tractions versus forces 227 9.12 Stress tensor 229 9.13 Exercises 238 10 Faulting 240 10.1 Introduction 240 10.2 Experimental fractures 240 10.3 Role of friction 241 10.4 Coulomb criterion 247 10.5 Limitations 250 10.6 Classification of faults 251 10.7 Faults and stresses 251 10.8 States of stress at depth 254 10.9 Magnitudes of stress components 257 10.10 Open fractures 261 10.11 Stress drop 262 10.12 Faults in anisotropic rocks 263 10.13 Oblique faults 264 10.14 Other limitations 266 10.15 Earthquakes 266 10.16 Exercises 267 11 Deformation 269 11.1 Introduction 269 11.2 Continuum assumption 273 11.3 Homogeneous deformation 276 11.4 Analysis of simple shear 278 11.5 Superimposed deformations 284 11.6 Inhomogeneous deformation 287 11.7 Deformation and related tensors 290 11.8 Exercises 300 12 Strain 302 12.1 Introduction 302 12.2 Deformed grains 302 12.3 Deformed fossils 304 12.4 Deformed pebbles 306 12.5 Geometry of the strain ellipse 309 12.6 Mohr Circle for finite strain 313 12.7 Pole of the Mohr Circle 315 12.8 Strain from measured angles 316 12.9 Strain from measured stretches 321 © in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-74583-3 - Structural Geology: An Introduction to Geometrical Techniques, Fourth Edition Donal M.