Structural geology A. Nicolas, 1989. Principes de Tectonique. 2nd edition, Masson, Paris, 223 pp., fig., price: FF 138.00 (paperback). The second edition of Principes de Tectonique by A. Nicolas differs from the first one published in 1984 only by a better printing quality and some minor revisions. The success of this book, attested by English and Spanish translations (1987) shows that it meets a real requirement in geology. In this small book, the author makes reviews of the present-day knowledge and hypotheses on deformation of rocks and the resulting geological structures largely based upon physical arguments and experiments, but in a straightforward presentation requiring no mathematical development. Accordingly, no local or regional description is given, but an account of the general principles and analytical elements leading to the interpretation of field observations. The book is divided in eight short chapters completed by three annexes. The three first chapters are devoted to the theory of strain: strain and stress (15 p.), theory of discontinuous strain (19 p.), continuous strain mechanisms (23 p.). The next five ones concern the structures developed in response to discontinuous strain (17 p.), then homogeneous strain (17 p.) with their interpretation (17 p.), continuous heterogeneous strain (22 p.) and finally folds (24 p.). The annexes are related to the tensorial analysis of strain and stress (17 p.), the measure of finite strain (21 p.) and the cyclospherical representations (11 p.). The text is clear and concise, supported by
numerous figures and rather comprehensive although limited to the main points; among other matters a good account on the role of fluids and on the deformation at the crystal scale is given. However, a too compendious treatment is sometimes prejudicial to a rigorous formulation and somewhat dogmatic. On account of the shortness there is no discussion which could disclose the complexity of structural problems and the difficulty of interpretations. The figures portraying natural cases are only illustrations of the text developments without an explanation of their context and localization. It is unfortunate that there is no concrete example which shows a better understanding of the application of theoretical principles to prevent against abuse of criteria uncommonly univocal. This book is not intended for specialists but may be very useful for non-structural geologists; they will find the meaning of most of the French terms used in structural geology (unfortunately without their English equivalents) and also an easily readable and accurate account on the theoretical principles and methods. It may be very valuable too for students in an elementary course if it is supplemented by a more practical teaching to counterbalance the dogmatism of the text. But for those wishing to go further, the abridged bibliography of five or six titles at the end of each chapter, without any orientation, is quite inadequate: the only reference to the 568 pages of J. Ramsay (1967) or to the 705 pages of A. Nadai (1963) is not the good way " p o u r en savoir plus".
Maurice Lelubre, Toulouse