Sporopollen record during Mid-Late Pleistocene from West Ujimqin Banner, Inner Mongolia, and its paleoclimatic significance

In order to reconstruct the paleoclimate and explore its evolution model and response to the global paleoclimate during the Mid−Late Pleistocene in the Bayinhua Basin, West Ujimqin Banner, Inner Mongolia, the sporopollen of ZK03 and ZK04 in the basin were systematically identified. Combining Coniss analyze with Co−existence Approach, we quantitatively reconstruct the palaeoclimate parameters in research area. 68 genera are identified and divided into 3 assemblages as: (Ⅰ) Pinus−Betula−Typha assemblage; (Ⅱ) Quercus−Ephedra−Artemisia assemblage;(Ⅲ) Cyperaceae−Typha−Polypodiaceae assemblage. The age of assemblage Ⅰ and assemblage Ⅱ was Middle Pleistocene, while the age of assemblage Ⅲ was Late Pleistocene. The vegetation types experienced the transformation as broadleaved − steppe type with a small amount of coniferous forest vegetation→broadleaved − steppe type vegetation→savanna− steppe vegetation. Palaeoclimate experienced three periods of transition from relatively warm and humid climate to relatively warm and cool semi−arid climate and then to relatively warm and humid climate. The annual average temperature and annual rainfall corresponding to each period also showed a numerical process of change from high to low and then to high. The trend from cool to warm at the turn of the Middle Pleistocene/Late Pleistocene can be well coupled with the trend of global mean temperature that indicated by the oxygen isotopes of Greenland ice core.