230Th dating of stem carbonate deposits from Tai Cuo lake, western Tibetan Plateau, China

The saline lake Tai Cuo, located in western Tibetan Plateau, China, is a closed endorheic basin mainly recharged by meteoric water and groundwater. Carbonate sediments, mainly showing stem structure, are extensively developed in the first terrace of Tai Cuo lake area and are over 3 m thick. The U-series method has been applied to those carbonate deposits. Sieved carbonates samples, smaller than 0.595 mm (#30) and larger than 0.177 mm (#80), were the research object for 230Th dating. The results indicate that the uranium contents are high, up to 6∼14 ppm, and activity ratios of 234U/238U range from 1.533 at the top to 1.437 at the base of the succession, indicating that the sedimentary environment was relatively stable during the period. Ages obtained with precision of 1∼3% have recorded environmental evolution history in this area during the period 13,340∼5200 yr BP, with an error bar of only 240∼89 yr, and are consistent with the lithological deposition sequence and greatly improved compared to previously published 230Th chronologies. This chronology will be of great importance for interpreting the environmental changes in the study area.