Ordos basin was part of the North-China platform in the early Paleozoic

while the western Qilian geosynelins was located on oceanic crust.In between them

there was a trunsitional continental slope inclined westward.This tectonic setting had played a evident part in controlling the formation of marginal depression in western Ordos from Paleozoic to Jurassic.The hinge line of the westward dipping continental slope mightbe located at about 107癊.Carboniferous sediments of "depression type"are developed to the west of 117癊 along the mid-north segment of the west margin ordos basin

and farther east are sediments of "wide-spread type"The later distributed widely in the northern Ordos basin are less worth oil and gas prospecting.The hinge zone is lithologically developed with various transitional facies and altenated each other where the best association of oil source and reservoir rocks may occur.Moreover

oil and gas.originated in the marginal depression might have migrated toward the eastern area since the Late Paleozoic.So

there should be an area of good hope for oil and gas prospecting.