Marine Dispersal of Fluvial Sediments as Fluid Muds: Old Concept, New Significance
Kristina A. Rotondo, Samuel J. Bentley, Sr., 2004. "Marine Dispersal of Fluvial Sediments as Fluid Muds: Old Concept, New Significance", Depositional Processes and Reservoir Characteristics of Siltstones, Mudstones and Shales, Erik D. Scott, Arnold H. Bouma
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Fluid muds are high-concentration near-seabed suspensions of fine sediments, and have been recognized in coastal sedimentary systems for many years. However, in the past decade, fluid-mud development and transport have been identified in an increasing number of settings as important mechanisms for marine dispersal of fluvial sediments. It has been shown that the combination of high-energy benthic hydrodynamics and sufficient fine sediment can result in cross-shelf gravity-driven flows (on very low slopes) that can blanket hundreds of square kilometers to thicknesses exceeding 10 cm. The sedimentary fabric that results from gravity-driven flows consists of a stacked pattern of predominantly fine-grained, fining-upward packages. The resulting morphology of the shelf can be a clinoform, with maximum deposition occurring on the foreset (convex-upward) region. The western Louisiana inner shelf has been experiencing fluid mud deposition in response to increased fine sediment supplied by the Atchafalaya River since ∼1950’s. A review of observations collected during recent studies of the Eel and Fly rivers, and their similarities to the Atchafalaya shelf indicate that wave-enhanced gravity driven flows are responsible for the sedimentary features and clinoform morphology present along the Chenier plain coast of Louisiana.
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Siltstones, mudstones and shales have been studied mainly with regard to general transportdeposition processes and clay mineralogy. A small group of investigators, with differing backgrounds, have worked on these fine-grained deposits. Recent studies on deepwater deposits from cores and outcrops indicate that the presence of finer-grained deposits greatly affect the fluid flow properties of deepwater reservoirs. Characteristics and rock properties of these deposits, which resulted from a variety of depositional processes, are just beginning to be understood.