The Yanchang Formation located in the north of Qinling-Qilian Orogenic Belt a forming part of Palaeo-Tethys Orogenic Belt.Because of its ultra-thick sedimentary layer,the abrupt changes of sedimentary facies,and the recording of the vanishing process of Qinling Ocean in late Triassic,it has drawn much attention at the southwestern margin of Ordos Basin in North China block.It even gives rise to the uncertainty of the uplifting time of Qinling-qilian orogenic belts and the suspicion of the existence of sedimentary provenance in southwestern Ordos basin during late Triassic,which attachs importance to the question whether there developed sedimentary provisions from the Qinling-Qilian Orogenic Belt during late Triassic in the Southerwest Ordos basin,and if there did,were they from the same origin?