Published:January 01, 1975
1975. "Bed Configurations", Depositional Environments as Interpreted from Primary Sedimentary Structures and Stratification Sequences, J. C. Harms, J. B. Southard, D. R. Spearing, R. G. Walker
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When fluids like air and water flow over beds of loose sediment at velocities great enough to transport some of the grains, a great number of different kinds of bed geometries can result, depending on the nature of the flow and the nature of the sediment. Study of these bed geometries, together with the modes and rates of grain movement on and above the transport surface (with which we will not be directly concerned), constitutes a major part of the field of “sediment transport mechanics” or “sedimentary physics”, whether practiced by engineers or by geologists. Engineers are concerned with bed geometries mainly because of the effect on the flow itself; geologists, on the other hand, are more concerned with what bed geometries can indicate about what the generating flows were like.
The aim of this chapter is to summarize the present state of observational knowledge on bed configurations, with particular emphasis on the continuing evolution of what we know from observation and also of the framework within which we think about bed configurations and organize the data. Most of the discussion deals with features produced by unidirectional flows, simply because our knowledge of features produced by more complicated flows is not yet good enough to be very useful in interpretation. Rather than trying to produce an exhaustive catalog of geometry and kinematics of the various bed features, we have aimed at making some important points about the major bed forms which will figure in interpretations in later chapters. Also
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Depositional Environments as Interpreted from Primary Sedimentary Structures and Stratification Sequences
The focus of these notes is on the use of primary sedimentary structures and stratification sequence as tools for interpretation of depositional environment of clastic sediments, emphasizing advances in understanding that the authors judge to be important. To accomplish the primary objective, several topics have been selected. Experimental flume studies are summarized with emphasis on work which extends the understanding of distribution of bed forms over increased ranges of grain size, flow depths, or velocity. Studies of modern and ancient sedimentary sequences are used to illustrate and interpret environments of deposition. Fluvial sediments are reviewed to show how experimentally derived generalizations are applied or qualified to interpret natural environments.