The Tectonic Restoration Research On Thrust Belt Structure Of Dalongkou In The Northern Of Bogda Mountain

The areas between orogenic belt and sedimentary basins, which is rich in oil and gas resources, are always the main areas for oil and gas exploration at home and abroad. The piedmont of the northern border of Bogda is located between Bogda orogenic belt and Junggar Basin. It plays a very important role in oil and gas exploration to study the structural feature and tectonic evolution history of the piedmont of the northern border of Bogda.This study identified nine geological surfaces by the field investigation and predecessor's information. Using integrated geophysical interpretation method, four 2D seismic profiles have been explained. Combining seismic geological interpretation, previous data and typical profile explanation, current structural patterns were explained. In addition, a tectonic reconstruction for four profiles was conducted.Research results can be concluded as follows: ?. nine tectonic surfaces exist in the northern border of Bogda and its adjacent region, including C₁ and C₂l, P2l-h and P3q, T1sh and T2k, T2-3x and J1-2sx, J2x and J2t, J3 and K1, E1-2Z and K2d, the Pliocene and Miocene, plane of unconformity between Paleogene and Quaternary. ?. The imbricate thrust structure of the south to north is the basic style in the research area, there are three structural development from the south to the north: the first row structure-the nappe structure located in south of Demon Mountain Fault, is Carboniferous strata mostly; the second row structure- the nappe structure located in north of Demons fault and south of the Fukang fault thrust, is mainly the Permian strata; Fukang fault is the boundary fault of thrust nappe system, the footwall strata located in the north of Fukang fault developed relatively intact autochthonous system with little distortion, which is the third structure. ?.By recovering four profiles, it can be found that the shortening of research area was no more than lkm in indosinian period, which indicated that tectonic activity is not strong. In the Yanshanian period, the shortening of research area was about 3km or even more, indicating that tectonic activity is relatively strong. A prototype of Bogda mountain was developed in this period. In the Himalayan period, the shortening of research area was more than 10km, which indicated that tectonic activity is violent owing to the strong extrusion pressure from the north and the south in the Himalayan period. This period is the main uplift period of Bogda mountain and the present structural framework of Bogda mountain takes shape in this period.