Eastern Qiulitag Displacement Transfer Structure and Its Evolution in the Kuqa Fold-Thrust Belt, Tarim Basin: Discuss Concurrently the Trap-Forming of Lateral Ramp-Related Anticline
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P548.2

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    Abstract:

    In the Kuqa fold-thrust zone, a lateral ramp-related displacement transfer structure is developed in the eastern Qiulitag structural belt. The strata broken by the eastern Qiulitag thrust, a north-dipping blind thrust fault, gradually decline from east to west, that is, Neogene salt and gypsum rocks west of Well Dongqiu 5 are transformed into Paleogene salt and gypsum rocks in Well Dina 201, and then into Jurassic coal measures in Well Dina 11, which is very distinctly delineated in the seismic cross section. The eastern and western fault flat is respectively in the Neogene salt and gypsum rocks of the Jidike Formation and in the Jurassic coal measures, and a lateral ramp is developed in a combined structure with coal in the upper and salt in the layer position. The recovery of structural evolution sections such as DQ99-196, DQ00-226, DQ00-263, indicates that the displacement gradient of the salt-in-the-upper-part stratum is around 103.72 m/km in the eastern Qiulitag structural belt, while that of the salt-in-the-lower-part stratum is about 61.65 m/km in the eastern Qiulitag-Dina subsection. On the above seismic sections, the positions of the axial lines of the salt-in-the-upper-part anticline and those of the salt-in-the-lower-part hidden anticline are relatively changed: they deviate southwards from east to west in the latter case. Besides, the outcrops show that folding is enhanced westwards in the salt-in-the-upper-part anticline. The structural subsection of the eastern Qiulitag structure in the strike direction suggest that sudden displacement of the lateral ramp divides it into two sections: the western section is named the Kuqatawu structure and the eastern section is called the eastern Qiulitag-Dina structure. The salt-in-the-lower-part anticline in the Kuqatawu structure is a kind of fault-related fold, which is controlled by the eastern Qiulitagh thrust, and the anterior and posterior fault flat is in salt and gypsum rocks of the Jidike Formation and Jurassic coal measures. The hidden structural wedge and the southern Qiulitag back-thrust constitute the Kuqatawu triangle zone. The hidden anticline in the eastern Qiulitag-Dina sector has a similar style as that of the Kuqatawu section, but there fewer back-thrust faults on its southern with no triangle zone. The dating age of the apatite fission track of the eastern Qiulitag structural zone shows that the lateral ramp can be traced back to the Kangcun Period. The formation of the lateral ramp-related anticlines in the eastern Qiulitag belt are related with a combination of two associated parts: a blind thrust from north to south and regional sinistral shear-compression. The main characteristics of the lateral ramp-related anticline are that the lateral ramp can adjust the strain differences between the upper and lower slip layers and serves as a channel of hydrocarbon between source rocks and reservoirs. In this way, gas can move from coal source rocks up to lateral ramp-related anticline traps. That is the case of the Dina 2 gas pool.

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YANG Minghui~ ),JIN Zhijun~ ),LU Xiuxiang~ ),SUN Dongsheng~ ),PENG Gengxin~ ),LEI Ganglin~ ) ) Basin & Reservoir Research Center, China University of Petroleum, Key Laboratory for Hydrocarbon Accumulation, Ministry of Education, Beijing,) Inst.2006. Eastern Qiulitag Displacement Transfer Structure and Its Evolution in the Kuqa Fold-Thrust Belt, Tarim Basin: Discuss Concurrently the Trap-Forming of Lateral Ramp-Related Anticline[J]. Acta Geologica Sinica,80(3):321-329

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  • Revised:November 14,2005
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