Late Quaternary sedimentology and geochronology of small playas on the Southern High Plains, Texas and New Mexico, U.S.A.

Playas are small, circular basins forming a ubiquitous component of the southern High Plains landscape. They are filled with carbonaceous mud deposited since the terminal Pleistocene. The stratigraphy and geochronology of 30 playas was investigated to better understand the paleoenvironmental record of basin filling. At the base of the fill in some playas is a well sorted eolian sand dated between ~ 13,000 and ~ 11,00014C yr BP. The beginning of mud deposition, representing aggradation of eolian dust on a moist, vegetated playa floor was largely between ~ 12,000 and ~ 10,50014C yr BP. Playa filling slowed ~ 9000 to ~ 400014C yr BP, probably due to dry conditions, increased ~ 4000 to ~ 200014C yr BP, then slowed again. Eolian sand and loam, likely representing regional aridity, accumulated in some basins episodically just prior to ~ 10,70014C yr BP, between ~ 8600 and ~ 470014C yr BP, and at ~ 130014C yr BP. Stable C isotopes from one basin indicate that the playa was inundated only seasonally throughout the record beginning ~ 11,50014C yr BP. The phytolith record in that basin indicates an abrupt shift toward cooling ~ 11,400 to ~ 11,20014C yr BP and then increasing importance of xeric-adapted C4grasses through the Holocene.