There is no need to argue about the value of structural geology. Geologists appear to be unanimous in stressing its usefulness both in pure science and in industrial applications. It is, moreover, an essential part of the education of a geologist even in such diverse fields as mining geology, petrology of igneous and metamorphic rocks, and petroleum geology. Petroleum geologists, for whom this text is primarily written, make continued use of structural geology during the course of their professional activities. In fact, petroleum geology is based essentially on structural geology and stratigraphy.
This book is designed to give petroleum geologists the structural knowledge they will need for their profession. The structures of sedimentary rocks are naturally emphasized, and particular attention is given to structures which are important in the discovery or development of oil and gas fields.
In this volume the relations of structural geology to stratigraphy have been stressed, for it appears that this will make the work more useful. The stratigraphic aspects of structural geology have come to be recognized fairly recently, and it appears that they are a promising field for investigation. Furthermore, it is generally recognized that promising traps for oil or gas accumulation which are of purely structural origin are steadily becoming scarcer compared to those produced wholly or partly by stratigraphic causes. Since the stratigraphic-type fields are likely to become of increasing importance in petroleum geology, it is desirable to understand thoroughly their structural features and relations.
This text is designed to be used with the writer's previous book, " Principles of Petroleum Geology."1 In order to avoid unnecessary repetition, subjects treated thoroughly in one book have in general not been discussed at length in the other. When it is necessary to treat the same subject in both books, as in the case of unconformities and salt domes,____________________