Abstract:

In this paper,a systematical description of tectonic attributes and history of evolution of the western Ordos margin is made from the viewpoint of plate tectonics. It is considered that the margin evolved from pre-Caledonian aulacogen through post-Caledonian aulacogen,via Mesozoic front depression to Cenozoic graben. An relative account of tectonic patterns,sedimentary characteristics,transgressive direction,magmatic activities and stress action of defferent times are given. The authors point out that the development mechanism of the above structures depends mainly on long-term convergence of north Qilian geosyncline and the adjacent Alashan block as well as dextral shearing of BaojiQingtongxia deep fault.The present area is characterized by sediments of huge thickness which formed a good few sedimentary cycles favourable to oil generation and preservation. Oil prospects of this area could not be underestimated though intensive reformation has later occurred in this area. The authors suggested that the hinge zone lying in between the area studied and Ordos platform,i. e.,the thrustclad area,should be promissing for oil and gas,when the middle Ordovician and the middle-upper Carboniferous are considered as rock sequences favourable to oil generation.