East Pamir Arc Piedmont Structural Characteristics And Geological Significance

Breakthrough advance of oil-gas exploration in foreland basin and thrust belt in abroad has been achieved, which is much valuable for researches on southwestern Tarim. By studying structural style, the formation and evolution of Pamirs arc structure belt, which is the most intensive collision and compression area in Qinghai-Tibet tectonic movement. We can know further about the history of Pamirs and western Kunlun collision orogenesis. It also can provide foundation for collisional uplift and thrust process of northern Qingzang plate, and at last as a direction to oil-gas exploration at foreland and thrust belt of southwestern Pamirs.Basing on geologic section and seismic data, this paper discusses the structure, composition, formation and evolution of eastern Parims structural belt, by using geology, petrology, sedimentology, geochemistry and geophysics knowledge. It is believed that the structural feature of nappe structure of Parims submountain region, from root zone to foreland zone, is thick-skinned structure to thin-skinned, and in the plain it is apparent zonality and sectionlization.The nappe structure is transverse to the strick of the orogenic zone, and divides into root zone, middle zone, frontal zone and outer zone from south to north according to the altitude of thrust fault, intensity of deformation, distribution of klippe, and clad relationship between autochthon and allochthon.Through the surface structural manifestation of extruding stress, the eastern Pamirs can be divided into three sections, each of which has different extention forms of thrusting and liberation ways of stress.The seismic interpretation indicates that the nappe structure extends to foreland mainly with the piggyback imbricate thrust fault, and the overlying strata forms fault-propagation fold by the affection of faults.The eastern Pamirs arc experiences three main compressional orogeny, which is separately in the early Paleozoic, the end of Paleozoic, and the Cenozoic. Among the three orogeny, the Himalaya tectonic stereotype period is the strongest one. At last, three main target exploration area has been proposed by researching the source bed, reservoir, seal and the evolution of basin.By using the rule of balanced cross section, the stratum reduction is about 8.7km and the contraction is 23.2%. Basing on the movement distance of the klippe, the minimum nappe displacement distance is 39km. The analyzing of apatite fission track suggests that the orogen uplift rate of Pamirs Mountain is 0.21mm/a to 0.29mm/a from 13.2Ma to 9.4Ma.