M. Stute, J.F. Clark, Columbia University

F.M. Phillips, New Mexico Institute of Mining and Technology

D. Elmore, Purdue University

The climate history (temperature and precipitation minus evaportranspiration) of southern Texas was reconstructed for the past 35 ka, based on groundwater data from the Carrizo aquifer. Paleotemperatures derived from noble gases dissolved in groundwater indicate an mean annual temperature 5degrees C lower than today for the last glacial maximum. Recharge rates (a measure of precipitation - evapotranspiration) were estimated from Cl- and from 36Cl concentrations after performing corrections for variations of atmospheric Cl- and 36Cl deposition rates. The two lines of evidence are consistent and indicate that the recharge rate between 16 and 20 ka was up to 100% higher than today. The occurence of high lake levels in the Great Basin during that period suggests that the shift to a wetter climate during the late glacial was a common feature of the southwestern US.