The Characteristics And Evolution Of Thrust Nappe Structare In The West Margin Of Ordos Basin

Based on fully using the predecessor's achievement in geological research, this paper carried on detailed investigation and research about the geological structure and sedimentary characteristics of the key region of the Zhuozishan-Helanshan, Niushoushan-Liupanshan in the west margin of Ordos basin, testified and falsified some controversial or unclear problems, the new views and main research progress as follows:1. The deposition-tectonics evolutionary history in the west margin of Ordos basin include 6 stages: crystalline basement formation stage in the Archaean-Terminal Palaeoproterozoic, stable continental-margin deposition stage in Middle-late Proterozoic-Ordovician, starting stage in the Caledonian thrust nappe structure, marine-continental alternation and inland lake basin formation stage in the late Palaeozoic-Triassic, dominant development stage of the thrust nappe structure in the Jurassic-Neogene period and continuously thrusting nappe stage in the Cenozoic period. Multistage thrust nappe structure function in the west margin of Ordos basin associated with the multistage foreland basin formation in the Devonian period (Liupanshan region), Jurassic-Cretaceous period and Palaeogene-Neogene period (partial region).2. The thrust nappe structure system in the west margin of Ordos basin consists of thrust fault system, nappe /thrust bodies/fold-thrust belts /foreland or back extentional basins, thrust sheets, thrust and its companionate structure. The system is divided into 5 first order structure, 11 second order r structure and 26 third order structure units; elaborated the structure characteristics of each unit in detail.3. The northern segment in the west margin of Ordos basin is a compound thrust system of the Henanshan, including the Alashan crystalline thrust sheet and autochthones or allochthones thrust structure system of north China, its front is continental margin fold-thrust belt of the Zhuozishan-Hengshanpu; There exists at least 3 stage thrust functions.The first stage took place in the Terminal Jurassic period, had at least three large-scale thrust functions along the three main detachment surfaces of the crystalline basement.The second stage formed the large-scale Zongbieli-Zhengyiguan allochthone nappe which has upper-lower double structure layers ,its main detachment is the coal bearing strata of the Carboniferous-Permian system, and constituted complicated duplex and link thrust. The third stage pushed the Ordovician System of the lower allochthone nappe to the Earth's surface in the western part, while in the eastern part formed continental margin fold-thrust and recoil fault belts in the meantime.4. There exists at least 4 stage thrusting functions in the Liupanshan arcuate thrust system of the southern segment in the west margin of Ordos basin, of which have no involvement of crystalline basement; The thrust nappe function of the first stage (Terminal Caledonian) mad the western Silurian uncomfortable terrace towards...