Aridification of central Asia during late Oligocene and Early Miocene has been documented by numerous eolian records from the North Pacific and central Asia. However, direct evidence of aridity from the interior of the arid zone is still rather scarce. To better reconstruct the climate history in central Asia during the late Oligocene, we have analyzed ostracod assemblages and gypsum content in the sediments from the lacustrine Jingou River section in the northern Tianshan Mountains. Our results show that the cold water species Candona cf. Neglecta and Pseudocandona albicans replaced the warm water species Ilyocypris bradyi and Ilyocypris sp. to become the dominant species at 23.8 Ma, indicating significant cooling in central Asia at that time. At the same time, a substantial increase in gypsum content indicates the intensification of central Asian drying. The synchronous cooling and drying approximately coincided with the Oi2b.1 and/or Mi1 events, implying a causal linkage between late Oligocene global cooling and central Asian aridity.
