Fault that show compresso-shear pattern in plane and intersecting inprofile is called compresso-shear vertical-intersecting fault. Within the studyarea

since the sides of major mountains and uplifts were controlled bycompresso-shear vertical-intersecting faults

a structural framework whicharranged alternately in fault-uplifts and fault-depressions was formed under theeffect of unified stress field of the plateau. In the east part of the region

thefault uplift-fault depressed zone resulted by NWW (Xiyu System) compresso-shear vertical - intersecting faults and four uplift - depression alternatedzones resulted by NNW (Hexi System) dextral shear-compression verticalintersecting faults conjoined to form four dextro-diagonal basin zones asWuwei-Lintao

Minle-Hualong

Jiudong-Xinghai

Jiuxi-Gjarring and Ngoringlakebasin zones. In the west

NWW stretched compressive fault uplift-faultdepressed zone and NEE striking conjugated compressive sinistral diagonalzone (Altun Mountains)

conjoined to form Kumkuli-Jiuxi sinistral diagonalbasin zone. The Jiuxi Basin is a ladder-shaped basin placed at the joint partof two conjugated shear-compressive zone whereas the Qaidam Basin is a hugecomplex fault-depressed basin which is between two shear-compressive zonesduring the Meso-Cenozoic. The formation regime of the basins is not thatof rift

but that of compresso-rift which is between faults dipping backeach other. In the Qaidam Basin

a structural framework which is arrangedalternately in uplifts and depressions is also formed by the above men-tioned vertical-intersecting faults and it controlled the evolution of the basinand also the generation.accumulation of hydrocarbon. The Qaidam landmasswas disintegrated in the Indo-China Epoch

and a piedmont fault-depressionwith faults in marginal areas and overlaps in its inner part was formed. Inthe early stage

its subsidence center and depocenter was in the north (T

J

K) and west (J

K) margin. As the compression of the Indian Plateenhanced

these centers transfered gradually to the central (N

2

) and eastparts of the basin.