Geological environment of Upper Triassic sediment in Shigouyi region of western Ordos Basin and its geological significance

The integrated analysis of the tectonic setting and regional stress field in western Ordos Basin and the rate of sedimentation,clastic composition and sedimentary filling shape in Shigouyi region in Late Triassic shows that the west margin of the Ordos Basin in Late Triassic was in overthrust-compression structural environment. The foredeep depression was formed by the compression function of foreland overthrust belt,and its provenance was the recycled fold-thrust belt. Compared with typical foreland basins,the Ordos Basin,in front of the thrust belt,is a quasi-foreland basin. The overthrust-compression in Shigouyi and the uprising in Liupanshan reveal that the fold-thrust belt in Niushoushan-Luoshan is the southwest boundary of the Ordos prototype basin in Late Triassic and the Upper Triassic sediment in Shigouyi region is of the margin of Yanchang Formation of the Ordos Basin. The new recognigation is beneficial to indicate more prospects of petroleum exploration in Mesozoic and Paleozoic in the west margin of the Ordos Basin.