A New Thick-Skinned Structure Model for the Kedo Thrust Belt in the West KunLun Mount, Tarim Basin, Northwestern China

Guizhong, Wang; Jianwei, Zhang; Peiling, Ma; Changwei, Han; Dongming, Ling; Bo, Xu; Xiangzhou, Zeng

Kedo thrust belt is located in the transition zone of West Kunlun piedmont tectonic belt in Tarim basin. The belt, composed mainly of thrust faults and folds, is interpreted to have formed under nearly N-S directional, strong compressional stress during late Cenozoic.

During the past decades, many scholars have considered that the Kedo thrust belt as passive-roof duplex, similar to the Alberta-style (the thin-skinned triangle model). This model is widely and successfully used in the gas and oil exploration of Kuqa depression, northern Tarim Basin. However, our study shows that the Kedo thrust belt is quite different from the Alberta Style: (1) the deep strata experienced several "open-and-close" periods, thus the strata were strongly faulted and fractured; (2) the anhydrite beds in the middle strata is only 0-100 meters thick, and its plasticity is poor; (3) the shallow strata are incomplete, and contain faults; (4) the geological outcrops randomly distributed. In addition, the thin-skinned triangle model is not consistent with drilling, outcrop, new seismic data, and other data. So the thin-skinned triangle model can not be applied in Kedo thrust belt.

By using the seismic data acquired by wideline and large array after 2007, in combination with large amounts of information of drilling, outcrop, field survey, digital sand box simulation results, three-dimensional modeling, and digital outcrop technique, we propose a new tectonic model. In this model, the Kedo thrust belt is interpreted as thick-skinned structure, and faults are considered as mainly basement-involved type of reverse listric fault which has a steep-dip in lower portion and gentle-dip in upper portion. The fault displays positive flower structure, is asymmetric, and gradually pinch-out in the shallow strata. The major differences between the viewpoints of this study and others' include: (1) the fault is interpreted to occur in the basal Cenozoic strata which cuts into the shallow formations rather than as passive roof detachment faults paralleling the shallow strata; (2) steep-dip rather than gentle-dip faults might have occur in the deep-buried strata. Strike-slip faults perpendicular to the structural trend are well developed. The Kedo thrust belt is divided into three Secondary tectonic belts from east to west by strike-slip faults. According to the new structural model, Kedo #1 condensate gas reservoir was discovered in 2010.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013