Cenozoic Structure Features Of Wupoer Area In Northeastern Margin Of Pamir

Wupoer is located in the Northeastern margin of Pamir, occupying the transitional zone of Pamir plateau, Western Kunlun, Tarim basin and Southwestern Tianshan. This area has important scientific significance because the Cenozoic strong deformation caused by the collision between Indian and Eurasian plate. Moreover, this area has practical significance because it is the key oil and gas exploration area. In this thesis, geological survey, geophysical data like CEMP and seismic profiles, combined with borehole data, have been used to determine the structural architecture, deformation patterns and their evolution. Following conclusions have been drawn.First, interpretation of CEMP and geological survey results indicate that south of the study area is controlled by northward thrusting of Pamir thrust belt. Middle part is dominated by deep-seated blind thrust system and Quaternary piggy-back basin patterns in the shallow, which both are the results of activity of Wupoer fault. North part is occupied by Kashi depression, filled by huge Cenozoic sediments.Second, 3-layered architecture is evident in the east segment of the study area. Shallow layer is Quaternary piggy-back basin. Middle layer is dominated by imbricate structures, consisting of Neogene thrust sheets. Deep layer is occupied by duplex structures composed with pre-Cenozoic sequences.Third, geological survey discovered Pliocene overlies Paleogene in an unconformity, with Miocene sediments absent in the hanging wall of Wupoer fault. While in the basin area, Miocene sequences are evident. This implies that Wupoer fault activated during end Miocene to early Pliocene.Forth, Wupoer area initiated its Cenozoic tectonic activity at end-Miocene to early-Pliocene, indicated by northward thrusting of Wupoer fault belt. By end of Pliocene, intense deformation was prevailing as a result of sustained thrust of Pamir tectonic knot. Since early Pleistocene, three unconformities are evident, between Xiyu Formation and underlain strata, between mid- and lower-Pleistonece, and between Pleistocene and Holocene. Hanging wall of Wupoer thrust fault has been discovered to be thrust over Holocene strata, which implies that the Wupoer fault continues activity at present.Fifth, balanced-section results indicate shortening of an order of 38.9-48.6 km, while shortening rate reach 55.4-48.4%. Deformation intensity decreases eastwardly.