F.M. Phillips, M.G. Zreda, New Mexico Tech

T.L. Ku, S. Luo, University of Southern California, Los Angles

Q. Huang, Salt Lakes Institute, China

D. Elmore, P.W. Kubik, P. Sharma, University of Rochester

The western Qaidam Basin contains numerons hydrologica!ly dosed lakes and playas. We have measured uranium, thorium, and chlorine radioisotopes in sediments from drill cores at two of these, Gasiktde Lake and Dalangtan dry playa, in order to date cycles of high and low lake level. The sediment chronologies from the two sub-basins are generally concordant, and the U/Th ages indicate transitions from high to low lake levels at 302 +- 56 ka, at 138 +- 6 ka, and at 16.3 +- 2.2 ka. These ages indicate that high lake stands in the Qaidam Basin were terminated at the end of continental glacial maxima. This result is unexpected because previously the large eolian dust fluxes out of Central Asia during glacial maxima have been considered to be associated with increased aridity in the region, not increased humidity. The lacustrine evidence, combined with previous data from ice cores, suggests instead that the persistence of strong winds may have played a more important role in enhanced dust fluxes than did variations in dust availability due to changes in aridity.