Samuel J. Bentley, Sr., 2003. "Wave-Current Dispersal of Fine-Grained Fluvial Sediments Across Continental Shelves: the Significance of Hyperpycnal Plumes", Siltstones, Mudstones and Shales: Depositional Processes and Characteristics, Erik D. Scott, Arnold H. Bouma, William R. Bryant
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Recent studies of fluvial-marine sediment dispersal have demonstrated that, under conditions of adequate sediment supply and intense turbulence in the bottom- boundary layer, wave-enhanced gravity flows can develop on shelves with gradients <0.7°. These conditions can exist seasonally on many continental shelves proximal to river mouths. Therefore, such flows (and resultant deposits) are probably more widespread than previously thought. Examples from a high-energy active-margin setting (Eel Shelf, California) and a lower energy passive margin (Atchafalaya River/Louisiana Inner Shelf) indicate that similar bedding can be produced by high- concentration near bed flows in apparently contrasting depositional settings, due to the occurrence of similar physical processes in the bottom boundary layer. Because such hyperpycnal flows can carry much more sediment mass than can buoyant plumes of suspended sediment, and can move at velocities on the order of cm s-1, such benthic sediment flows on shelves could represent a significant and previously underestimated transport mechanism for fine sediment across continental shelves.
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Siltstones, mudstones and shales have been studied mainly with regard to clay mineralogy and general transport-deposition. Recent studies on deepwater deposits from cores and outcrops have shown that fluid flow properties of deepwater reservoirs are greatly affected by the presence of finer-grained deposits in the reservoir. Initial analysis indicates that the majority of these finer grained deposits have a large silt component and are closer to siltstones rather than mudstones, commonly called shales To date, little attention has been given to their characteristics resulting from different depositional processes.