Evolutionary char-acteristics of the Jiuquan basin and character of the Kuantaishan-Heishan fault on the northeastern margin of the Qinghai-Tibet Plateau

The Kuantaishan- Heishan fault, located on the north side of the Jiuquan basin and to the south of Huahai- Jinta basin, intersects with the Altyn Tagh strike- slip fault at the western end. Comparative study of the Cretaceous basins in the Jiuquan basin shows that the basins on either side of the Kuantaishan- Heishan fault have different basement natures and sedi- mentary characteristics though the basins then were mostly downfaulted ones and all controlled by E- W extensional tectonics. The Cretaceous strata in the Jiuquan basin, Changma basin and the North Qilian fold belt have the same Early Paleozoic basement and exhalative sediments and basalt interbeds are developed. The North Qilian marginal fault was not active in the Cretaceous. The Huahai- Jinta basin has the high- grade metamorphic pre- Changchengian basement,and in the basin exhalative sediments are not developed. The Kuantaishan- Heishan fault is an important lithospheric shear fault, which controlled the sedimentary and tectonic evolution of the Cretaceous basins on its both sides.