Pollen evidence for the environmental context of the early Pleistocene Xiashagou fauna of the Nihewan Basin, north China

The Xiashagou fauna is one of the most abundant and representative faunas in East Asia and can be directly compared to the Olivola fauna of early Late Villafranchian age in Europe. Therefore, it is of great significance for understanding the evolution of the Quaternary faunas and environment of East Asia. We conducted pollen analyses of 163 fossil samples and 1045 surface samples, combining the results from the NHA drill core to characterize the patterns of vegetation and climate change in the Early Pleistocene and the early stage of the Xiashagou fauna. The results enable the definition of three cold periods (2.6-2.58 Ma, 2.55-2.34 Ma, 2.20-2.14 Ma) and two warm periods (2.58-2.55 Ma, 2.34-2.20 Ma). The pollen assemblages are dominated by Picea or Artemisia, Amaranthaceae and Poaceae during the cold periods, while dominated by Pinus and broadleaved trees during the warm periods. The annual average temperature (Tann) decreased by similar to 2 degrees C (up to similar to 10 degrees C), and average annual precipitation (Pann) decreased by similar to 200 mm (up to similar to 500 mm) during the cold period. The Xiashagou fauna emerged at the beginning of the third cold period (similar to 2.20 Ma) with Tann decreased by 3-4 degrees C and Pann by 100-200 mm, when the pollen spectra are dominated by Artemisia, Amaranthaceae and Poaceae (>80%), indicating that the vegetation was predominantly grassland. From 2.19 to 2.18 Ma, the climate became slightly warm and humid, with increased Pinus and Ulmus representation, which resulted in the development of forest; after 2.18 Ma the climate became colder and drier again. (C) 2020 Elsevier Ltd. All rights reserved.