Early Pleistocene (Olduvai Subchron) vegetation and climate change based on palynological records from the Yinchuan Basin of northwestern China
Abstract Many recent studies focus on the relatively cold and humid interval during the Early Pleistocene Olduvai Subchron (1.95–1.77 Ma), but detailed environmental records for this interval are still rare. Here we present a high-resolution pollen record from the PL02 core (38°55′26.62″N, 106°36′3.82″E) from the Yinchuan Basin of northwestern China to reconstruct vegetation and infer climatic changes. Vegetation was dominated by desert steppe from 1.95 to 1.89 Ma suggesting a cold and dry climate. High percentages of Picea and Abies pollen indicate cold and humid conditions between 1.89 and 1.87 Ma while pollen percentages of broadleaved taxa increased rapidly between 1.87 and 1.84 Ma reflecting relatively warm and humid conditions. Palynological assemblages from 1.84 to 1.82 Ma reflect a colder and drier climate with an increase in xerophytic taxa and a decrease in conifers. Further increases of xerophytic taxa suggest a relatively cold and dry climate prevailed after 1.80 Ma. The new high-resolution palynological record suggests that environmental changes in the Yinchuan Basin are synchronous with global fluctuations. The inferred climate fluctuations show 20-kyr cycles during the Olduvai Subchron, supporting the view that climate changes in the study region were mainly controlled by orbital factors.