Geochronology of Playas Lake, Southwestern New Mexico

Playa lake basins contain valuable archives of late Quaternary paleoclimatic conditions in the southwestern United States. Previous research on lake basins in the region has revealed several pluvial intervals post-dating the last full glacial period; however, the timing of these intervals can only be assessed through the collective analysis of individual lake-level histories. While previous studies of lake core sediments have provided baseline data for climate modelers, the accuracy of most lake chronologies has been limited by uncertainties associated with 14C reservoir corrections. Further, most studies have used the sedimentological, chemical, and biological characteristics of lake sediments to infer relative lake-level. In contrast, radiocarbon-dated shoreline deposits—although unfortunately rare—can provide accurate information about the timing and duration of high stands, as well as a record of absolute lake-level during these events. Recent investigations at Playas Lake, NM, provide preliminary geochronological and paleoenvironmental information about two previous high stand intervals, represented as carbonate units within relict shoreline deposits. Both carbonate units contains an abundance of minute gastropods of the Succinidae family, which has been shown recently to yield reliable radiocarbon ages. The results of ongoing investigations at Playas lake are presented here.