Geoarchaeology of the Boca Negra Wash Area, Albuquerque Basin, New Mexico, USA

Dozens of Paleoindian sites, including the Boca Negra Wash (BNW) Folsom site (LA 124474), are scattered across a basalt plateau (the West Mesa) on the western side of the Albuquerque Basin, and adjacent uplands. The BNW site, like many others in the area, is located near a small (∼60 × 90 m) playa basin that formed in a depression on the basalt surface and was subsequently covered by an eolian sand sheet (Unit 1) dated by OSL to ∼23,000 yr B.P. Most of the basin fill is ∼2 m of playa mud (Units 2 and 3) dating ∼13,970 ¹⁴C yr B.P. (17,160-16,140 cal yr B.P.) at the sand-mud interface to ∼2810 ¹⁴C yr B.P. (∼2960-2860 cal yr B.P.) at the top. C/N ratios suggest that the BNW playa basin probably held water more often during the Folsom occupation; stable carbon isotope values indicate C3 vegetation was more common as well, but C4 grasses became dominant in the Holocene. Cores extracted from four playa basins nearby revealed a similar stratigraphy and geochronology, documenting presence of wetlands on playa floors during the Paleoindian occupation of the area.