Abstract: There is a prolonged global hyperthermal period in the early Paleogene. Based on the analysis of fossil sporopollen assemblages, from the lower first submember of the Kongdian Formation to the lower third submember of the Shahejie Formation in the Dongying Depression, we systematically analyzed the paleoclimate evolution process of the Dongying Depression during the early Paleogene. We selected 23 kinds of fossil sporopollen species with statistical significance, and quantitatively classified these species into 5 categories (thermophilic, mesothermophilous, coldtolerant, xerophytic and hygrophytic groups) on the basis of three climate parameters: MAT, CMT and PER. According to the temperature index (TI) variation trend, the temperature evolution process of the Dongying Depression during the early Paleogene can be divided into three stages: continuous hot, warmhot alternation and continuous warm periods. Accordingly, the humidity evolution process can be divided into four stages: droughtpluvial alternation, continuous drought, second droughtpluvial alternation and continuous pluvial periods in terms of the humidity index (HI) variation. There were obvious hysteresis effects in the humidity evolution relative to temperature evolution in this prolonged hyperthermal period that went on from 53.89 to 47.48 Ma, with a total duration now estimated to be 6.41 Ma. Through identification of the specific strata corresponding to three worldwide greenhouse warming events in the Paleogene in the Dongying Depression, the pivotal effect of the ETM2 and EECO events on the hyperthermal period in the Dongying Depression is confirmed. In addition, by combining paleoclimate and lithofacies analyses, the control of paleoclimate over sedimentary system in the lacustrine basin is clarified.

Key words:  Paleogene, paleoclimate evolution, fossil sporopollen, warming climatic events, Dongying Depression