Kuqa Depression, The Eastern Section Of The Piedmont With The Structural Characteristics

Foreland basin is rich in oil and gas and foreland thrust fault belt is the focus of current exploration. More than twenty both large- and small-scaled foreland basins have been found worldwide. Over the years, exploration on the Kuche foreland basin makes significant breakthrough and it indicates a prosperous future on gas and oil exploration. Hence, it is of great importance to study structural characteristics of the piedmont belt, eastern Kuche Depression.In this paper, a tentative study on the post-Cenozoic successions in eastern Kuche Depression, with a focus on the structural evolution history of these post-Cenozoic rocks within the depression area, has been done. On the basis of this study, it is possible to illustrate spacial and temporal relationship between piedmont and buried structure, and to discuss timing and evolutionary history of the piedmont belt. In addition, this study also can provide insights into the investigation of southern Tianshan structural belt and post-Cenozoic successions within the Tarim Basin as well as provide new data for the study of regional orogenic belt.On the basis of filed investigation and geophysical data, both surficial and subsurface structure of the Yiqilike, Tuziluoke, Tugeermin, and Dongqiulitage anticlines as well as both quantitative and semi-quantitative analysis of the evolutionary sections and stratigraphic contact relationships of strata with different ages, have been documented in this paper and conclusions are summarized as following:(1) Previously recognized angular unconformity between the Yageliemu Formation and underlying successions is more like a conformity and/or parallel unconformity and thus impact comes from the late Jurassic Yanshan movement is weak.(2) The Yageliemu and Shushanhe formations occur in northern wing of the Tugeermin anticline, while the absence of coeval successions in southern wing is due to denudation occurred during post-Shushanhe Formation period.(3) Extensively occurred angular unconformity between the Jidike Formation and underlying successions is actually an overlap, which indicates intense late Yanshan movement after deposition of the Shushanhe Formation. (4) There was a sub-surface upswell in the Tugeermin area during the Late Triassic and Early Jurassic. Formation of the Tugeermin and Yiliqike anticlines initiated during the late Yanshan movement. Formations of the Tuziluoke, Qiutage, and Yake anticlines started when the Kuche, early and late Xiyu (eopleistocene) formations were depositing, respectively.(5) On the basis of two equilibrium sections' reconstruction of the eastern Kuche Depression, it was suggested that the deformation of piedmont belt, eastern Kuche Depression has been progressively increased from the Oligocene. Calculated distance that resulted from structural shortening is 26 km. Given that the shortening started from the Oligocene, a shortening rate of 1 mm/a can be obtained.