This photographic atlas illustrates the structures and other geometric aspects of sediments and sedimentary rocks. It has been translated into English from the 1992 second Italian edition, with some modifications and additions. The first edition, dating back to 1970, was directed mainly to students graduating in earth sciences; it was more technical than the present one and required some previous knowledge of sedimentology and geology. The second edition has been written in a more accessible style and is addressed to students approaching sedimentology and sedimentary geology for the first time. It should also pique the interest of amateur scientists and people who are curious about natural objects. These specific objects, i.e., sedimentary strata and their features, are visible to the naked eye in several places: mountainous areas, river banks, seashores, quarries, and road cuts. A book like this can thus be used as a sort of guide to a large, open-air museum to be visited on foot or, in many cases, also by car. I wish to point out, however, that it is not a complete catalog of these phenomena.
In sediments and sedimentary rocks, structures represent what lineaments are to a face; they reveal the sediment or rock character and reflect its origin. Their shape often has the elegance and the grace of sculpture, painting, and tapestry.
Many other aspects of sediments--chemical and mineralogical composition, texture, physical, and technical properties--can be observed or measured. All of them are useful for identifying and characterizing sedimentary products. They have been covered in other books and manuals on sedimentology, both general and specialized, but a previous knowledge of their content is not necessary for reading and consulting this book. Here, basic concepts and processes are introduced along with the description and presentation of sedimentary structures; this is done in the simplest possible way, which obviously cannot satisfy a reader who demands every detail. The point is that you do not need to read other books on sedimentology or geology before enjoying this one. In this sense, Sedimentographica, although dealing with only one aspect of sediments and consequently being complementary to other works, can claim a certain autonomy: you can approach it with the support of the essential scientific basics learned in high school. Frequent analogies are made with objects and phenomena familiar to everyday life to ease understanding of processes and mechanisms; many cross-references also help the reader to compare, contrast, and discriminate among structures.
All kinds of structures, both primary and secondary, are dealt with in this atlas. They are grouped into broad genetic categories; not every specific type, however, is illustrated. The main purpose is not to show all known structures but a selection of the most significant ones, reflecting the more basic and representative processes that act on sedimentary materials: water currents, waves, glaciers, wind, tides, gravity, living organisms.
I cannot avoid a certain bias toward examples and areas more familiar to me, but I have tried to remedy this as much as possible by using pictures taken during excursions to various parts of the world or asking colleagues for them. Approximately 70% of the images are from Italian environs, 30% from the rest of the world. Italy is famous for its vast collection of manmade monuments and art treasures, less for its natural rocks and geology (except, perhaps, for the active volcanoes and the Serapes market with its perforated columns, immortalized by Lyell's treatise). The book will show that this small area at the center of the Mediterranean is also a repository of geological treasures. In particular, the mountainous backbone of the Italian peninsula boasts many superb exposures of ancient carbonates, evaporites, and deep-water deposits, including classical examples of turbidites.
The photographic documentation of sedimentary structures is immense: at least 1,500 references can be quoted for the last twenty years. The main inconvenience is that most of this iconographic material is scattered among too many papers, generally but not always available in university libraries: only a few general articles and textbooks exist (see References). Among them, the atlas of Pettijohn and Potter (1964) stands out as a milestone, and has greatly influenced the original project of this book.
Providing a tool for geological curricula and fieldwork is the main purpose of an atlas, but not the only one; not the least of my intentions, especially in preparing a new edition, was to attract the curiosity of the layperson and to make the public at large more aware of earth science phenomena. Sedimentary structures, after all, are out there to be used not only for technical or scientific purposes, but simply to be looked at; they are "forms that show themselves to the world" (A. Portmann 1969).
The book is dedicated to the memory of a person who encouraged me and made the first edition possible--Delfino Insolera, whom friends remember for his curiosity about nature, his love of science as a human achievement, and his great ability in communicating his enthusiasm to other people.
I wish to thank all the colleagues and students who kindly provided pictures and suggestions. In particular, I want to express my gratitude to Guido Piacentini and Vanna Rossi, two photographers gifted with a bright and delicate touch, who provided many fine images. My thanks also to Paolo Ferrieri, who printed the 2,000 pictures that served as a base for the final selection; to Maria Angela Bassetti, who helped prepare the pictures, the glossary, and the index; to my wife, Nevia, who read the text and improved the language; and to researchers and technicians of the Institute for Marine Geology of C.N.R. in Bologna, who opened their archive of cores and seismic records to me.
My last thought, however, is for several generations of students, who suffered before, during, and after examinations, and thus helped to reveal deficiencies, limits, and inconsistencies of the first edition.