Palynological record of Pliocene climate events in North China

The pollen flora of the Yushe Basin is dominated by Arternisia, Chenopodiaceae, Ulmus and Pinaceae. Carya, Carpinus and Juglans/Pterocarya are represented by lower values, but, being thermophilic, are of ecological significance in the pollen flora. Repeated appearances of the thermophiles along a continuous pollen sequence provide a good opportunity to produce a climate index curve for calibration of some significant temperature variations between 3.2 and 2.0 Ma. Pollen analysis of the Yushe Basin reveals several important Pliocene climate features. There is a temperature-declining trend with cyclic oscillations between about 3.2 and 2.0 Ma. A warm phase is recorded at about 3.05 Ma and a cooling event, at about 2.5 Ma that can be correlated with the marine record. The lengths of oscillations are estimated to be about 40-60 ka, which probably implies some astronomical influence(s) on the ancient climate of North China. (C) 2002 Elsevier Science B.V. All rights reserved.