早更新世甘肃省临夏盆地的环境演化

Evolution of early pleistocene environment in Linxia basin,Gansu province

以孢粉分析为主,结合w(CaCO3),c(Cl-)和粒度指标,建立了临夏盆地早更新世的环境演化序列.临夏盆地早更新世环境演化大致经历了干(2.50～1.91Ma)湿(1.91～1.80Ma)干(1.80～1.76Ma)三个阶段,其中在1.89～1.87Ma期间云杉孢粉含量占绝对主导地位(77.8%～89.4%),是临夏盆地早更新世气候最湿润期.通过将孢粉资料同北大西洋深海底栖有孔虫氧同位素曲线和南海浮游有孔虫氧同位素曲线对比以及孢粉波谱分析发现,1.95Ma前后是临夏盆地气候转型的重要时期.在此之前,气候变化主要受热带季风控制,之后受高纬冰盖变化的驱动.根据前人相关研究结果推测,青藏高原在早更新世的强烈隆升可能是造成这一气候转型的原因之一.

Based mainly on the spore-pollen analysis, combining with w（CaCO3）, c（Cl^-） and grain size, we reconstructed a sequence of early pleistocene environmental changes in Linxia basin. It was divided into 3 phases： arid（2.50-1.91 Ma）-wet（1.91-1.80 Ma）-arid（1.80-1.76 Ma）. Especially, during 1.89-1.87 Ma, the content of Picea pollen was the highest （77.8%-89.4%）, indicating the humidest period during the whole early pleistocene. The climatic shift of early pleistocene in Linxia basin might have occurred near 1.95 Ma, by comparing the pollen data of shrub and herb with the north Atlantic deep-sea benthic oxygen isotope curve and the south China sea oxygen isotope curves of planktonic foraminifera. Moreover, were mainly controlled by the tropical monsoon before and spectral analysis results show that climate changes after 1.95 Ma, but after 1.95 Ma they were driven by the high-latitude ice sheets changes. According to previous research, we presumed that strong uplift of the Tibet plateau in the early pleistocene might be one of the reasons of climate changes.