Tectonic Evolution,Strike-slip and Thrust Reformation of Hoxtolgay Basin in Northwestern Xinjiang, China

Hoxtolgay basin, located in northwestern Xinjiang, is a Mesozoic-Cenozoic sedimentary basin developed on the thrust nappe system of the west Junggar orogenic belt formed in late Paleozoic. There exists an ongoing debate in understanding of the basin prototype and its evolutionary history in Mesozoic-Cenozoic period. To restore the history of formation and evolution, and determine the type of the basin, research ideas of reformed basin was applied to analysis of formation and development of the basin, the comprehensive geological studies and seismic structural analysis were carried out as well. Results show that the formation and evolution of Hoxtolgay Basin in Mesozoic-Cenozoic age is mainly influenced by west Junggar orogeny, and can be subdivided into at least three basin formation and reformation periodssince Triassic, respectively Indosinian, Yanshanian and Himalayan period. The prototype of the basin in Indosinianis a compressional depression controlled by the east-westtrending Xiemisitaishan piedmont thrust fault, and developed an extensional depression with a large scale subsidence in Yanshan period. At late Yanshanian, the basin was strongly reformed by folding and thrusting, and the north-south ramp framework of the basin wasformed. The sedimentary area of the basin was greatly narrowed and restricted to the middle depression belt of the basin in late Yanshanian to Himalayan period, and mainly exhibited the characteristics of the reactivity and inheritance of the pre-existing faults. Although the tectonic stress fields and basin features are different in different stages of formation and development of the basin, their regional tectonic stress fields are generally the same or similar in the later stage of each basin development, mainly due to Xiemisitaishan Piedmont fault thrusting southward and Daerbute sinistral transpressional faulting. It is therefore concluded that Hoxtolgay basin is generally a strike-slip and thrust reformed basin caused by the changes of the regional tectonic stress fields in the process of basin evolution.