塔里木盆地西部色力布亚断裂和康西断裂的主要特征及活动时代

塔里木盆地西部麦盖提斜坡和巴楚断隆两大构造单元的分界线的西段,原称色力布亚断裂带,呈北北西—南南东向展布,长约120km。本文基于系统的地震剖面解释,认为该断裂带内包括了切割深度、倾向和活动时代等均有不同的两条断裂,西部仍称色力布亚断裂,东部由本文新命名为康西断裂。前者是基底卷入型冲断层,由不同级别的背冲构造与主干断裂构成复杂的断裂带,向南东变窄;主干断裂向北东倾,中新世活动,背冲断层在上新世仍有活动。康西断裂是盖层滑脱型冲断层,向南西倾,加里东期活动,之后长期稳定,更新世复活。区域上,色力布亚断裂属巴楚北北西向断裂系,康西断裂属塔中北西向断裂系。这些新认识可能成为麦盖提斜坡区油气勘探的新思路。

Main characters and active ages of the Serikbuya and Kangxi flauIts in the western Tarim Basin

The western segment of boundary fracture between the Markit Slop and the Bachu Fault-Uplift in the western Tarim Basin was once called the Serikbuya fracture zone. Based on a systematic analyses of seismic profiles, the paper thought that the Serikbuya fracture zone included, actually, two faults with obviously different dissected depth, dipping and active age. The western sector of the fracture zone was still named the Serikbuya fault, which was a basement-involved fault, composed of a series of lower-order back-thrusts and became narrower southeastwards. The major Serikbuya fault dipped to the northeast and activated in Miocene, with some branch back-thrusts activating in Pliocene. The eastern sector of the fracture zone was renamed the Kangxi fault by the paper, which was a fault of superficial detachment. The Kangxi fault, dipped to the southwest and activated in the Caledonian movement, which rejuvenated in Pleistocene after a long-term stabilization. Regionally, the Serikbuya fault attached to the Bachu NNW-striking fracture system which created in Miocene and stretched northwards into the Kalpin area(the South Tianshan Cenozoic intracontinental orogen), while the Kangxi fault attached to the Tazhong(central Tarim) NW-striking fracture system which created in the Caledonian orogeny. The recent study demonstrated that the Central Tarim Lower Uplift was a multiple oil-gas accumulation play, so the new understanding for the former Serikbuya fracture zone might support a new thinking for oil-gas exploration in the Markit Slop. The obduction of the Bachu Fault-Uplift along the Serikbuya fault resulted in the Paleozoic and Eogene of the Markit Slop area deepend buried further, and the thick mudstone and siltstone of Pleistocene was a good capping bed for oil-gas. To analyse the role of Serikbuya fault both in early stage of petroleum accumulation and later stage of gas-filling adjustment, the oil-gas exploration in the Markit Slop area should have a new breakthrough in near future.