Zheng Benxing, Wang Sumin
The lake basin area in the source of the Yellow River is a tectonic depression zone since Neozonic. During the Tertiary, there was a typical high peneplain with a lot of hills and lower mountains of 500～1000 m a.s.l. In those years, the climate was warm and humid. There were a lot of karst features appeared on the limestone massif and red debris deposits in the piedmont, with large paleolakes. Up to the end of the Tertiary, the plateau uplifted and the climate turned to cold, but it was still a bigger lake basin during the early Pleistocene, and in the Xixiabangma Glaciation, no glacier developed in these mountains because the snowline altitude was over the altitude of the mountains. During the Cahaxili Glaciation of the middle Pleistocene, there were glaciers developing in the Bayan Har, Zarijia, Buqingshan and Anyemaqen Mountains and four big ice caps with a diameter of about 30～50 km. Up to the late stage of the middle Pleistocene, penultimate glaciation, glaciers extended downward to valleys and Ngoring Lake was a large glaciofluvial lake. Some lakes such as Xinxinhai Lake on the north slope of the Mianshaling range also appeared. During the last glaciation of the late Pleistocene, medium valley glaciers developing in the mountains and the climate was cold and dry with strong wind. In Mianshaling area the eolian sand deposited largely and the glaciofluvial lakes shrank, because the lake water outflowed eastwards owing to neotectonic fault with a direction of east-west. The Yellow River system became connected together and a large of water with sand from lake area of the source of the Yellow River run into the Zoige Lake area. In the middle of the Holocene, lake area greatly shrank and large lake bench and valley plain with a dry grassland appeared, and meanders in the Yellow River were developing.
