RELATIONSHIPS BETWEEN LANDSLIDE FORMING MECHANISMS AND CLIMATE CHANGES SINCE EARLY MID-PLEISTOCENE IN THE UPPER REACHES OF YELLOW RIVER AND THE THREE GORGES RESERVOIR AREA
中更新世早中期以来黄河上游与三峡库区滑坡形成机理与气候变化关系研究

The relationships between landslide forming mechanisms and climate changes are one focus in the landslide study in recent years.In the study,paleo-landslides and modem landslides since the early mid-Pleistocene in China were studied and the relationships among the landslide active period,climate change,and the climate change-driven mechanism of landslide were also done.It was found three characteristics.1) Landslide development would be closely related to climate changes.Most landslides developed in warm and wet periods,such as in marine oxygen isotopic odd stages (MIS).Rapid and continuous climatic fluctuation periods usually were also high-frequency active periods of landslide.2) There are 3 active periods of paleo-landslide in the region of Longyang Gorge to Liujia Gorge of the upper reaches of Yellow River.Landslides in the first active stage,whose OSL and ESR dating ages are 24～35kaB.P.,developed on the 3~(rd)～4~(th) fluvial terraces of Yellow River.Landslides in the 2nd active stage,whose ages are 5kaB.P.,developed on the 2nd fluvial terraces of Yellow River.Modern landslides in the 3rd active stage developed on the 1st fluvial terraces of Yellow River.The study shows that the Gonghe tectonic movement caused the region uplift and in turn strong down-cutting erosion along the river to form 300～600m steep slopes.In addition,the rapid climatic fluctuation in the MIS 3 induced landslide development of the first stage.During 5kaB.P.of Holoeene Optimal,strong monsoonal rainfall and a large number of melted snow and ice converged into the Yellow River to lead landslides development of the second stage.Modern landslides were mainly trigged by human activities.3)In the Three Gorges Reservoir area,there also were 3 high-frequency periods of landslide since early mid-Pleistocene,which were corresponding to warm and wet climatic periods.Since the later mid-Pleistocene,the amount of landslides obviously increased and the lasting time of landslide active period also lengthened.Particularly,most landslides developed on marine oxygen isotope stages,MIS 5 and MIS 3.During these two landslide active periods,the paleo-climate was warm and wet and a large amount of rainfall in Tibetan Plateau was converged into the Yangtze River to lead strong down-cutting erosion,and in turn to form cliffy slopes with weak slope stability and then a large of landslides.