Paleogene-Neogene deposits in the Tongtian River Basin, Qinghai and their geological implications

The integrated examination of stratigraphic sequences, depositional characteristics, provenances and sedimentary environments of the Paleogene-Neogene deposits in the Tongtian River Basin, Qinghai results in the construction of a vertical facies sequence, including the alluvial fan facies, delta facies and lake facies. During the Paleogene-Neogene, the provenance of the Tongtian River Basin was derived from the Kaixinling uplift in the north. According to the gypsum and limestone intercalations and grain sizes, the authors contend that the (climates) were hot and moist in the basin during the middle Eocene, hot and dry during the late Eocene, hot and humid during the Oligocene, and warm and wet during the middle Miocene. The uplifting of the (Qinghai-Xizang) Plateau is interpreted to be episodic.