Sedimentary structures and their relation to bedforms and flow conditions
Sedimentary structures that show up in outcrops and cores tell us about physical, biological and sometimes also chemical conditions at the time they were formed. Varying hydraulic or aerodynamic conditions result in assemblages of structures that often bear diagnostic features of sedimentary environments. Therefore an understanding of the origin of sedimentary structures and their assemblages is a prerequisite for sedimentologists and petroleum geologists involved in core description and interpretation. The main objective of this book is to bring together the present basic knowledge on the relation between sedimentary structures, bedforms and hydraulic conditions. The book is part of post-graduate Short Courses in Advanced Sedimentology and Stratigraphy for the petroleum industry offered by ENRES International. In these courses much attention is given to the recognition of sedimentary environments from diagnostic features of sedimentary structures and assemblages of structures. For this purpose practicals are given using a selection of lacquer peels and cores representing typical fluvial to estuarine, coastal and eolian environments. This material including its interpretation is published as a regularly updated stand-alone document that can be obtained from ENRES. One of the pioneering publications on this subject was a series of SEPM symposium papers published in 1965 (Middleton, 1965b). A more comprehensive publication on sediment movement by fluid flow and the resulting sedimentary structures was followed in 1972 (Blatt, Middleton and Murray, 1972). After that many excellent publications and textbooks were published (e.g. Allen, 1984, 1985; Bridge and Demicco, 2008; Collinson and Thompson, 1989; Harms et al., 1982; Hs?, 1989; Leeder, 1999; Reineck and Singh, 1980). These publications are partly covering a much wider scope as presented in this book, but are at some points not going into the desired details and are partly outdated. We have no intention to offer a new comprehensive textbook. The main goal of this book is to introduce the terminology and fundamental concepts that are necessary for the description and interpretation of the hydraulic background of sedimentary structures in siliciclastic deposits. Another objective of this book is to put this topic within the newly developed framework of modern stratigraphy (e.g. sequence stratigraphy and climate stratigraphy). Also some important new insights from recent research at the University of Utrecht and unique data of sedimentary structures from outcrops up to 15m below mean sea level have been added. A specially-designed Core Simulation software has been developed in cooperation with Statoil which will be used during the course and the practicals.