Elements of Structural Geology

Elements of Structural Geology

Slate with sandy laminae, showing two directions of shearing. Donnolly's Creek, Victoria. x 4

ELEMENTS OF STRUCTURAL GEOLOGY E. SHERBON HILLS Research Professor of Geology in the University of Melbourne CHAPMAN AND HALL LTD & SCIENCE PAPERBACKS

First published 1963 by Methuen & Co Ltd 11 New Fetter Lane, London E.C.4 Reprinted 1964, 1969,1970 Second edition 1972 published by Chapman and Hall Ltd 1963, 1972 E. Sherban Hills First published in Science Paperbacks 1965 Reprinted 1966, 1969, 1970 Second edition published as a Science Paperback 1972 ISBN-13: 978-0-412-20750-1 e-isbn-13: 978-94-009-5843-2 DOl: 10.1007/978-94-009-5843-2 Filmset in Photon Times 11 on 12 pt by Richard Clay (The Chaucer Press) Ltd, Bungay, Suffolk This book is available both as a hardbound and as a paperback edition. The paperback edition is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, re-sold, hired-out, or otherwise circulated without the publisher's prior consent in any form of binding "Of cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser.

Contents PREFACE TO SECOND EDITION PREFACE TO FIRST EDITION page VB viii THE DOMAIN AND CONTENT OF STRUCTURAL GEOLOGY II DEPOSITIONAL TEXTURES AND STRUCTURES 6 III NON-DIASTROPHIC STRUCTURES 49 IV PHYSICS OF DEFORMATION 78 V ENVIRONMENT, TIME, AND MATERIAL 106 Appendix: Mohr Diagrams 139 VI PLANAR AND LINEAR STRUCTURES AND JOINTING 143 VII FAULTS 164 VIII FOLDS 216 IX TECTONIC ANALYSIS OF FOLDS 261 X CLEAVAGE 295 XI MAJOR STRUCTURES AND TECTONICS 320 XII IGNEOUS ROCKS 356 XIII STRUCTURAL PETROLOGY BY E. DEN TEX 402 XIV GEOMORPHOLOGY AND STRUCTURE TECTONIC S INDEX OF AUTHORS INDEX OF SUBJECTS INDEX OF LOCALITIES MORPHO- 442 481 489 501 v

Preface to Second Edition During the ten years which have passed since the manuscript of the first edition of this book was completed, most of the topics to which the chapters are devoted have themselves been dealt with in important monographic publications, and it is increasingly difficult to condense the volume of knowledge and number of examples which may properly be grouped under Structural Geology, within one volume. I nevertheless believe that there is still a place for the general textbook, although its writing may, in future, well be a task for several collaborators. For this edition, complete recasting of the book was not practicable, but many errors have been corrected, references have been brought up-to-date, and certain sections have been rewritten, while others have been expanded to deal with new concepts. It is not long since, in an earlier work, it was apposite to refer to gravitational tectonics and flowage as a burgeoning branch of structural geology; but it must now be said that rigid-plate tectonics and ocean-floor spreading are even more remarkable concepts, which must have fundamental effects on regional structural geology and on our understanding of global phenomena. Additionally to the Journals mentioned in the Preface to the first edition, my thanks are due to the editors of the Journal of Geophysical Research and the Seismological Society of America, as well as to the authors concerned, for permission to publish illustrations in the revised edition. I am indeed grateful to the many colleagues who have suggested improvements in the book, among which it has been salutary to find that what is praised by some is criticized by others. I am also again much indebted to Professor E. den Tex (Leiden), who kindly consented to revise Chapter XIII on Structural Petrology. and to Miss Cecily Finlay for her constant help during the revision of the manuscript. University of Melbourne March 1970 E. S. H. Vll

Preface to First Edition The range of fundamental topics that should be included in a general work on structural geology is indeed very wide, but, despite the condensation needed to reduce these matters to a reasonable compass, I have tried to adhere to certain standards as to completeness of coverage, style of presentation, and adequacy of illustration. Particular attention has been paid to definitions, both for the realities of structures and for concepts and notions, since definitions, far from being dryas-dust material for rote learning, express much of what emerges from the systematization of knowledge, and it is desirable that the student should realize the extent to which they are conceptual and thus subjective. Experimental analogues and the relevant physical or chemical principles have been freely referred to, with as much discussion of pros and cons as is possible within the limits of a textbook. It is hoped that in these ways the reader may himself be induced to consider and weigh propositions, and thus to inculcate something of the author's own abhorrence of the cult of the fashionable theory, which so often in geology involves personal loyalties rather than intellectual integrity. and certainly does nothing to raise the scientific status of the subject. For the Chapter on Geomorphology and Structure I have, of necessity, relied upon Davisian or genetic geomorphology, partly because quantitative terrain analysis, despite the 'precise and coldly analytical' methodology claimed for it. has not yet so far as I am aware, included sufficient of structure in its premises to make it applicable to structural geomorphology, and partly because I have found Davisian principles, modified as required by new knowledge, most warmly satisfying in the field. It may, however, readily be foreseen that morphometric studies will in due course add their contribution to structural geomorphology and morphotectonics, at scales ranging from micro to megatectonics. For the latter. I have briefly referred to several generalizations and theories. but have emphasized the need for further precise knowledge as to the morphological and geological data. Palaeomagnetic results. although of great potential applicability in tectonics. are not discussed because the book deals mainly with the optically demonstrable features of rocks and rock masses, so that the implications of palaeoclimatology, the viii

PREFACE TO FIRST EDITION IX past distribution of animals and plants, the distribution of magma-types and such, and similar topics of significance in megatectonics are not dealt with. Although the principles of structural geology are of general applicability, the particular needs of oilfield geology. engineering geology, and mining geology call for certain specialized field and laboratory methods, including the geometrical processing of data according to the needs of particular problems. Detailed reference to such matters would be inappropriate in a book intended to deal with fundamentals, and indeed each of these specialities is itself treated in well-known textbooks. It is. however, well to note that, unless data are correctly diagnosed in the field, their geometrical processing is valueless, and the stress in this book is accordingly on the understanding of geological structures. although reference is made throughout to certain wellknown methods of representation and reconstruction of structures. The sequence of topics in my small 'Outlines of Structural Geology' has broadly been adhered to. as it permits a gradual introduction of notions, and appears to have been acceptable to many teachers, but I have not hesitated to make repeated reference to the same notion, for example, soft-rock deformation, under several headings. as the student often fails to transfer knowledge from one compartment of his mind to another. The Chapter on Structural Petrology was kindly written at my request by my former colleague in Melbourne. Dr E. den Tex, now Professor of Petrology in the University of Leiden, Netherlands. I am indeed grateful to him for having undertaken the difficult task of presenting this subject in a style and with a philosophy conforming generally with the rest of the book, and in so satisfying a manner in a single chapter. I am much indebted also to Dr J. V. Harrison of Oxford for critically reading the MS. and for assistance in various other ways. It is a pleasure to acknowledge the kindness of those numerous colleagues who over the years have sent me their publications from many countries. as I have tried to draw examples and illustrations from a wide area. geology being par excellence a global science. Acknowledgement is made to the under-mentioned Publishers, Journals, and Serials for permission to use previously published illustrations as a basis for line drawings specially made in a uniform style for this book. Acknowledgement to authors. and to the sources of half-tone illustrations other than the author's own photographs, are made in the captions. Addison-Wesley Press Inc., Edward Arnold & Co., Cambridge University Press, Julius Springer Verlag. McGraw-Hill Book Co. Inc., Macmillan & Co., Ed. Masson & Cie. Oliver and Boyd. Thomas Nelson & Sons, Ltd., University of Chicago Press. John Wiley & Sons, The Williams & Wilkins Company, American Association of Petroleum Geologists, American Geophysical Union. American Journal of Science. Economic Geology, Geographical Review. Geologie en Mijnbouw. Geologische Rundschau,

x PREFACE TO FIRST EDITION Geological Society of America, Geological Society of South Africa, Geological Magazine, Geologists' Association, Geological Society of London, Journal of Geology, Koninklijke Nederlandische Akademie Van Wetenschappen, Mineralogical Magazine, Neues Jahrbuch fur Geologie, etc., New Zealand Journal of Science and Technology, N.V. de Bataafsche Petroleum Maatschappig, Physical Society of London, Royal Society of London, Royal Society of New Zealand, U.S. Geological Survey, Geological Society of Australia, Geological Survey of Great Britain, Geological Survey of Victoria. My personal thanks are due to Miss P. Carolan and Miss C. Finlay for secretarial and technical assistance. University of Melbourne March 1961 E. S. H.