Shallow Marine Sands
Published:January 01, 1975
1975. "Shallow Marine Sands", 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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In this section we present four case history studies of shallow marine sand bodies to illustrate how sedimentary structures and their sequences can be used to interpret processes within a broad depositional environment for which there are few well-established models, based either on modern or ancient sediments. And, knowing that a number of processes operate in present-day shallow marine waters to create a complex, time-variable hydraulic regime, there probably cannot be anything like “THE” shallow marine sedimentation model. However, several appropriate shallow marine models can be suggested.
Compared to models discussed previously, relatively few offshore shallow marine models are described in the geological literature. No doubt the lack of knowledge of modern shallow marine sand bodies and their internal structures contribute to this deficiency. This opinion does not ignore the growing body of oceanographic data on modern shallow marine sediments (see Stanley and Swift, 1974). But what modern sediment studies commonly lack, particularly those in shallow marine or shelf settings is vertical control. For example, though morphological forms of modern equilibrium shelf sand bodies are continually being discovered, their internal structures are practically unknown. But what is so lacking from the modern is abundantly supplied by the ancient. Thus our knowledge of internal structure and sequence of shallow marine bodies comes from the ancient, unlike fluvial and shoreline environments where modern sediment studies have contributed significantly.
Is a thoroughly known modern model absolutely necessary to “validate” a depositional environment interpretation made of an ancient sedimentary rock sequence? We
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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.