The paleoclimate change of Qaidam Basin during the last 2.85 Ma recorded by Gamma-ray logging

The geographical location of Qaidam Basin corresponds to N36°05’-38°10’ and E90°10’-98°05’. The thickness of the Quaternary deposits in the basin reaches 2000-3000 m. This paper deals mainly with the aspect of paleoclimate change of the basin. The approach used for the study consisted of (1) establishing the paleoclimate curve of the basin according to the climate indices, including the spore-pollen statistics, carbonate content and δ¹⁸O, obtained from the samples of the 760 m continuously-cored exploration holes sited in the basin, (2) comparing the paleoclimate curve with the natural gamma-logs of the same exploration holes, and (3) determining the paleoclimatic changes in the last 2.85 Ma on the basis of detailed geochronological calculations. These results are extremely important for comparison with the δ¹⁸O-based climate curve derived from the ODP659 in the Atlantic Ocean and with the cycles of paleosol in the Chinese loess.