TH-230 U-234 AND CL-36 DATING OF EVAPORITE DEPOSITS FROM THE WESTERN QAIDAM BASIN, CHINA - IMPLICATIONS FOR GLACIAL-PERIOD DUST EXPORT FROMCENTRAL-ASIA/

The western Qaidam Basin contains numerous hydrologically closed lakes and playas. We have measured uranium, thorium, and chlorine radioisot opes in sediments from drill cores at two of these, Gasikule Lake and Dalangtan dry plays, in order to date cycles of high and low lake leve l. The sediment chronologies from the two sub-basins are generally con cordant, and the U/Th ages indicated transitions from high to low lake levels at 302 +/- 56 ka, at 138 +/-6 ka, and at 16.3 +/- 2.2 ka. Thes e ages indicate that high lake stands in the Qaidam Basin were termina ted at the end of continental glacial maxima. This result is unexpecte d because previously the large eolian dust fluxes out of Central Asia during glacial maxima have been considered to be associated with incre ased aridity in the region, not increased humidity. The lacustrine evi dence, combined with previous data from ice cores, suggests instead th at the persistence of strong winds may have played a more important ro le in enhanced dust fluxes than did variations in dust availability du e to changes in aridity.