Late Cenozoic central Asian drying inferred from a palynological record from the northern Tian Shan

Sediments contained in basins adjacent to great mountains provide opportunities to reconstruct the aridification history of central Asia. Here we use a palynological record from the fluviolucustrine Jingou River section collected from the northern Tian Shan, NW China, to reconstruct aridification in central Asia during the late Cenozoic. Biogeomagnetic results show that the section was continuously deposited through the interval 28-4.2 Ma. The palynological record, with the auxiliary of the principal component analysis and the diversity index, indicates that a late Oligocene wet condition existed in central Asia and shifted to dry conditions at 23.8-23.3 Ma. The dry condition remained until 17.3 Ma and subsequently ameliorated to a relatively wet stage to 16.2 Ma, but then began to increase once again and reached a peak at 13.5 Ma that last throughout the late Miocene and the early Pliocene. Comparing the aridification process to the global temperature trend and history of tectonics, we suggest that the long-term drying trend in central Asia is dominated by late Cenozoic cooling, while the dry events that occurred at 23.8-23.3 Ma and 16.2-13.5 Ma are more likely associated with regional mountain building. The land-sea redistribution further complicated the drying processes. (c) 2010 Elsevier B.V. All rights reserved.