The Palaeornorphologic Features of the Basement of the Jurassic Coal Measures and Its Control on the Sedimentation of Fuxian Formation in Yulin, Shaanxi

The palaeomorphologic feature is one of the primary geological parameters in basin analysis. This paper demonstrates the palaeomorphologic features of the basement of the Jurassic coal measures, the depositional characteristics of Fuxian Formation and the relationships between them in Yulin district. Ordos Basin. It has been revealed that there is a buried-valley Shenyu Buried-Valley) in the eastern study area, and a buried-hill (Wushenqi Buried-Hill) in the western. Fuxian Formation, which directly overlies on the basement with 0-131.11 mthick, consists of conglomerate, sandstone, mudstonc. claystone and coal line. The principal components recognized in outcrops and drill cores are alluvial fan. lacustrine beach, small delta, lacustrine, fluvial and swamp deposits. Controlled by the palaeomorphologic relief, the lacustrine environment dominated the eastern study area, the alluvial fan and fluvial environment developed in the northeastern and western parts, and in the transition part, the lacustrine beach and samll delta were deposited. As a whole, the general depositional features of the Shenyu Buried -Valley are determined by the associations between buried-hills and buried-valleys in Ordos Basin.