塔里木盆地巴楚-柯坪地区新生代断裂系统

A studying of Cenozoic fracture systems in Bachu-Kalpin area, Tarim Basin

巴楚隆起是塔里木盆地的一个次级构造单元,内部断裂系统走向以北北西向为主,北侧与之相邻的柯坪冲断带断裂走向近东西向,属于南天山构造体系。两个断裂系统在平面上呈近于正交的关系。巴楚隆起大面积缺失中、新生界,其内部断裂体系起始活动时间的确定较为困难。通过对巴楚和柯坪地区新生代层序特征对比研究及其接触关系分析,结果表明中新世巴楚隆起南北向断裂体系开始形成,向北一直延伸到柯坪构造带之中。两个构造单元的南北向断裂有较好的对应性。柯坪东西向断裂系统的主要活动期是上新世(N2)以后。现今柯坪构造带南北向和东西向断裂体系是不同时期构造的叠加。在此基础上,构建了巴楚和柯坪断裂体系形成的构造地质模型。

Strikes of fault system in Bachu uplift, a secondary structural unit in Tarim basin, are mainly NNW, while those in the neighboring Kalpin thrust belt to the north, part of South Tianshan tectonic system, are nearly EW. These two fracture systems are nearly orthogonal in the plane view. Mesozoic and Cenozoic are absent in a large area in Bachu uplift, so it is difficult to determine the exact time of activity of the fracture system. Comparing the features of Cenozoic sequences and analysing their contact relations shows that the N-S fracture system in Bachu uplift began to come into being in Miocene and extended northward into Kalpin structural belt. The corresponding relations between the N-S fracture systems in the two structural units are studied in this paper.It is pointed out that the E-W fracture system in Kalpin area was active mainly after Pliocene(N 2). The present N-S and E-W fracture systems in Kalpin structural belt are the results of superimposition of structures in different stages. Structural geologic models of Bachu and Kalpin fracture systems are also presented in this paper.