Abstract: 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.