Cenozoic Qaidam basin, China: A stronger tectonic inversed, extensional rifted basin

Qaidam basin is a composite sedimentary basin developed on typical continen tal crust. It comprises a Jurassic foreland basin and a Cenozoic extensiona l basin. The geologic history of the Cenozoic Qaidam basin can be divided i nto two megastages on the basis of stratigraphy and structure. The first me gastage, from latest Cretaceous to Oligocene, consisted of two periods of r ifting due to upwelling of the hot upper mantle. This is demonstrated by tw o tectono-sequences formed by the rifting, the synrifting magmatic thermal activity, and the control of protobasin development by syndepositional faul ts. The second megastage comprises three tectonosequences that developed in the Miocene and Pliocene and was a period of structural inversion that con sisted of compressive downwarping and reverse faulting. This tectonic inver sion may be ascribed to the long-distance propagation of compressive stress caused by the collisions of the Indian and Eurasian plates. The thick sequence of primary oil source rocks was deposited in the major r ifted depression and the restricted drainage graben of the rifted protobasi n. During the tectonic inversion megastage they were subject to deep burial and prolonged heating. A major and a minor oil-generating basin have devel oped. The tectonic inversion processes produced several structural features that may contain potential hydrocarbon reservoirs and traps.