The Rhame bed (Slope Formation, Paleocene), a silcrete and deep weathering profile, in southwestern North Dakota

The Rhame Bed is a unit at the top of the Slope Formation (for merly part of the Ludlow Formation ) in the Fort Union Group deposited during Paleocene time. The Rhame Bed was mapped in western Slope County and north central Bowman County. The bed outcrops on the tops of buttes, at the present groJnd surface in large level areas, or in steep slopes. Although the bed is laterally discontinuous, it is a clearly mappable unit. The Rhame Bed typically consists of two dominant lithologies: siliceous rock and white sediment. The siliceous rock is hard, gray, and made of silt-sized detrital quartz grains in a matrix of microcrystal line quartz. It contains abundant casts and molds of branches, stems or roots of plants. It is underlain by sediment that is white to medium gray, consists of sand, silt, or clay, is very irregular in thickness, and lacks calcium carbonate. Comparison of the Rhame Bed with similar material described in Australian, African, and European literature indicates that the material in the Rhame Bed is silcrete overlying a deep-weathering profile. It probably formed during a period of little erosion or deposition, under a stable land surface covered by thick vegetation, in a warm and humid climate