The lower portions of large delta systems typically consist of natural levee deposits which contain clay, silt, swamp peat, and organic-rich sediment. In the upper portions, the delta plain deposits are very similar to backswamp and floodplain activity of the fluvial environment. The delta plain deposits are usually thin and laterally discontinuous, except where thicker natural levees form. The deposits are often cut by younger distributaries which form channel fills.
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