塔里木盆地吐木休克构造带断裂构造分析

Tectonic analysis on Tumuxiuke fault belt in the western Tarim Basin

吐木休克断裂位于塔里木盆地西部,是一条大型基底卷入型断裂构造带,构成塔里木盆地次级构造单元阿瓦提凹陷和巴楚断隆的分界。根据系统的地震资料解释,可以将吐木休克断裂分为西段、中段和东段3部分,各段构造特征有所差异。西段,为单一的基底卷入型高角度逆冲断层,倾向巴楚断隆;中段,除倾向巴楚断隆的主冲断层外,倾向相反的反冲断层越来越清晰,楔状冲断构造的轮廓逐渐显现出来。同时,在断层上盘还发育第四纪正断层;东段,倾向巴楚断隆的主冲断层,向上断至中寒武统,未断开中寒武统以上的地层,其冲断位移量完全为倾向阿瓦提凹陷的反冲断层所吸收,形成典型的楔状冲断构造。根据地震资料解释,认为吐木休克断裂带主要存在两期断裂构造:深部高角度基底卷入型逆冲断裂带和其上叠加的浅部正断层。前者形成于库车组沉积前,在库车组沉积期间持续活动,并在新近纪晚期定型;后者是本次研究首次发现的,形成于第四纪早中期,仅发育在吐木休克断裂带的中部。

The Tumuxiuke fault belt, which locates in the western Tarim Basin, is a large-scale basement-involved fault zone and forms the boundary between the Awati Sag and Bachu fault- uplift（sub tectonic units of Tarim Basin）. Based on systematic interpretation on seismic data, three sections of different tectonic features can be divided：the west, the middle and the east section. In the west section, there only develops a basement-involved high-angle thrust fault which dips towards the Bachu fault-uplift; while in the middle section, besides the main Bachu- inclining fault mentioned above, a reversed-inclination recoil fault becomes increasingly clear and gradually draws the outline of wedge-shaped thrust structures. Meantime, on the upper plate of the recoil fault, a series of Quaternary normal faults develop ; however, in the east section, the Bachu-inclining main fault has its top stopped at Mid-Cambrian, while the unbroken strata above Mid-Cambrian have their thrust displacement completely absorbed by the Awati-inclining recoil fault, which finally make up of the typical wedge-shaped thrust structures. According to the seismic interpretation, we conclude that mainly two generations of fault tectonics exist in the Tumuxiuke fault belt： the deeper high-angle basement-involved thrust fault zone and the shallower overlaid normal faults. The former formed in early Neogene and finally stabilized in Late Neogene; the latter is a new discovery in this paper which formed in the Early-Middle Quaternary and it only developed in the middle section of the Tumuxiuke fault belt..