The planar distribution and significance of the organic reefs in the Lower Cretaceous Nangshan Formation in the Coqen Basin, Xizang

The Coqen Basin is located in the hinterland of the Qinghai-Xizang Plateau. Eight organic reef sections have been identified in the basin along the Qiekan-Guchang-Luobo-Dangqiongco fault zone. It is inferred, from the radiolarian siliceous rocks and volcanic rocks, that the fault zone should be a facies-controlling fault zone, where the deep-water deposits including platform-margin slope and basin deposits were once (accumulated). Afterwards these deep-water deposits disappeared within the fault zone due to subsequent reactivation of faulting. The organic reefs along the both sides of the fault zone should be assigned to the platform-margin reefs.