The presence of isolated sand bodies surrounded by mud and the scarcity of soil features suggest that Lower Holocene sediments reflect a period of rapid floodplain aggradation during which crevassing, lacustrine sedimentation, and avulsion dominated floodplain construction. Upper Holocene deposits contain abundant soil features, and sandy and silty soils are Entisols, Inceptisols, and Alfisols whereas clayey soils are Vertisols. Natural-levee silts and sands and well drained backswamp muds are present between meander-belt sands. Upper Holocene deposits (< 5000 yr B.P.) are represented by large Mississippi River meander-belt sand bodies that are up to 15 km wide and 30 m thick. Muds encase crevasse-splay and floodplain-channel sand bodies (< 1 km wide), and collectively these deposits represent a mosaic of shallow lakes, poorly drained backswamps, and multichannel streams, similar to modern examples in the Atchafalaya Basin ( approximately 100 km south of Ferriday). Lower Holocene deposits (> 5000 yr B.P.) consist of lacustrine and poorly drained backswamp muds that contain authigenic siderite, pyrite, and vivianite and show little evidence of soil formation. On the basis of differences in sediment grain size, sediment-body geometry, and the abundance of soil features, the Holocene deposits are subdivided into Lower and Upper Holocene units.
approximately 20 m) of sands, silts, and clays, which overlie Late Wisconsin sands and gravels.
Floodplain cores acquired near Ferriday, Louisiana show that Holocene deposits consist of 15-30 m (ave. The alluvial architecture and soil characteristics of Holocene Mississippi River floodplain deposits in the southern Lower Mississippi Valley provide evidence for significant changes in floodplain development in response to sea-level rise.
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