Palynological record of Pliocene climate events in North China

Abstract The pollen flora of the Yushe Basin is dominated by Artemisia , 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.