Sediment Provenance Analysis and Its Tectonic Significance in the Foreland Basin of the Ordos Southwestern Margin
Liu Shaofeng Ke Airong Wu Liyun and Huang Siji (China University of Geosciences, Wuhan 430074)
It is effective to determine thrust events of provenance, tectonic setting and provenance strata corresponding to basin sediments according to the clast dispersal style and the components of sediments in foreland basins. Test and study on the Upper Triassic stratigraphic section of the Ankou region in the southwestern margin of Ordos show that the provenances of stratigraphy are a set of meta clastics and meta volcanics which are Chenjiahe Formation (O 3 ch ) and Huluhe Formation (Z-O 2 hl ) contributed in teh eastern Qilian fold thrust belt. The provenance of the Upper Jurassic conglomerate in the southwestern margin is Longshan Formation (Pt 2 ln ). The dispersal style of the Upper Triassic is the blended clast composition, and the dispersal style of the both of the Upper Triassic and the Upper Jurassic is the inverted clast composition which is the sedimentary response to two times of large thrusting. The analysis on the QmFLt trianguler diagram representing the sandstone components of the Upper Triassic in the Ankou region shows that the Late Triassic basin in the southwestern margin of Ordos is a foreland basin located in the foreland of a collision orogen and the provenance is the fold thrust massif of the recycled orogen which is the eastern Qilian orogen.