Events of the Pleistocene left their mark on major US rivers. A conspicuous band of alternating Pleistocene and Holocene deposits characterizes the broad, flat alluvial plain of the Mississippi River Embayment, its tributaries to the west, and coastal Texas. The irregularly striped pattern owes its origin to extensive and accelerated deposition by streams during interglacial phases of the Pleistocene, followed by erosion of these materials by Holocene river systems, over the last 1-2 million years. - USGS