Abstract: The Hetao Basin in Inner Mongolia is a Cenozoic faulting basin. It is also called Paleo-Hetao Lake as an inherited and closed sag pond in the Late Pleistocene. The lake sedimentary system was mainly formed in the Late Pleistocene, encompassing the Donghecun, Wanshuiquan and Dalate Formations in its upper, middle and lower sections, respectively. As the lake basin continued to subside, the Dalate Formation was formed under semi-deep and deep lake sedimentary conditions in an alternating sulphate and carbonate water environment. In contrast, equilibrium between lake basin subsidence and sedimentation led to the formation of the Wanshuiquan Formation in shallow to semi-deep brackish waters. As the rate of sedimentation surpassed rate of subsidence, the Donghecun Formation was formed in brackish-water and at times in carbonate beach and shallow lake environment. At the end of Late Pleistocene, the Paleo-Hetao Lake experienced a high water period. River capture at the boundary between Inner Mongolia, Shanxi and Shaanxi, and strong fault activity and extremely powerful earthquake in the northern Hetao Basin, caused the outflow of the Paleo-Hetal Lake linking the Yingchuan and Hetao Basins and the gorge between Shanxi and Shaanxi to form the modern day Yellow River.

Key words: Hetao Basin, Paleo-Hetal Lake, Upper Pleistocene, environmental change, river capture, extremely strong earthquake, formation of Yellow River