The Blackwater Draw Formation (Quaternary): a 1.4 plus-m.y. record of eolian sedimentation and soil formation on the Southern High Plains

The Southern High Plains of NW Texas and eastern New Mexico are mantled by a vast (>100 000 km ² ) sheet of Quaternary eolian sediment locally as much as 27 m thick and termed the "Blackwater Draw Formation'. These sediments generally fine from SW to NE indicating the source area to the Pecos River valley. As many as six well-developed buried soils (2.5 YR to 5 YR hues, Bt horizons 1-2 m thick, Stage II-III calic horizons), similar to the regional Paleustalf and Paleustoll surface soils, occur in the formation. The buried soils indicate episodic sedimentation separated by long periods of landscape stability. Eolian sedimentation probably occurred during prolonged aridity, and stability and pedogenesis likely obtained during subhumid to semiarid conditions, similar to those of the late Quaternary. The presence of the 0.62 m.y. Lava Creek B Ash and 1.4 m.y. Guaje Ash in the formation shows that the deposit accumulated throughout most of the Quaternary. -Author