The large semi-elliptical to elliptical Rainwater Basins are the surface expression of older elliptical depressions developed in fluvial sands and gravels that are buried by a blanket of a thick sequence of layered loesses and associated paleosols. The loess, which overlies these features, consists of an undisturbed sequence, from bottom to top, of Middle Wisconsinan Gilman Canyon Formation (loess), a regional paleosol developed in Gilman Canyon Formation, Late Wisconsinan Peoria Loess, Brady Soil (paleosol) developed in the Peoria Loess, and Holocene Bignell Loess in which the modern soil has developed. This loess sequence lies upon a paleosol developed in the fluvial sands and gravels in which these depressions initially developed. Thus, the modern basin landscape is a direct result of the accumulation a few meters of loess that blankets an older basin landscape. These basins are palimpsest landforms created by the episodic accumulation of a blanket of loess over a prehistoric landscape with numerous basins.