Late Pliocene-Early Pleistocene normal faulting in Trim Basin（NW China）： A tectonic pause under the far-field effect of India-Asia collision
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摘要: 受控于印度—亚洲碰撞的远程效应，中亚地区的晚新生代挤压冲断构造异常发育，同时发育少量区域挤压构造背景下派生的局部伸展构造。以往的研究没有发现晚新生代区域性伸展构造。我们通过认真、系统的地震资料解释，在塔里木盆地发现一系列上新世晚期—更新世早期的正断层。这些正断层主要分布于塔里木盆地西部的阿瓦提坳陷、巴楚隆起、麦盖提斜坡以及塘古孜巴斯坳陷。正断层走向NW-SE和NE-SW，剖面上组合成堑-垒构造，仅塔里木盆地西北缘沿沙井子断裂带分布的上新世晚期—更新世早期正断层带组合成负花状构造，显示出张扭性断层带的特征。根据生长指数计算，正断层活动的起始时间是上新世晚期（ca.3 Ma），持续演化至更新世早期（ca.2 Ma），然后停止活动。这些正断层形成于一个弱的区域性伸展构造背景；这期正断层活动代表印度—亚洲碰撞远程效应下，中亚地区脉动挤压冲断过程中的一个构造间歇期。
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关键词:
- 上新世晚期—更新世早期（ca.3～2 Ma） /
- 正断层 /
- 印度—亚洲碰撞远程效应 /
- 区域性伸展构造 /
- 构造间歇期 /
- 塔里木盆地 /
- 地震解释
Abstract: Due to the far-field effect of the India-Asia collision, the Late Cenozoic normal faults are rather rare compared with the abnormally developed Late Cenozoic compressional structures in the Tarim Basin, a large Cenozoic sedimentary basin in the central Asia. The normal faults were often overlooked previously. The previous studies saw them as local structures derived from the compressional structures under the regional compressive tectonic setting. Our intensive systematic seismic interpretation discovered the Late Pliocene-Early Pleistocene normal faults in the Tarim Basin. They distribute mainly in the western half Tarim Basin. Two possible Late Pliocene-Early Pleistocene normal faults were found in the northeastern Tarim Basin. The normal faults appear both on tectonic unit boundary and within tectonic unit, in both rise and depression. They tend NW-SE and NE-SW forming a conjugated system horizontally, and combine into graben-horst structures or staircase-like cross-sections in profile. The Late Pliocene-Early Pleistocene normal faults in the Tarim Basin are regional but not local tensional structures. According to the fault growth-indexes, the normal faults were formed in Late Pliocene-Early Pleistocene. The normal faulting occurred in ca.3～2 Ma. The ca.3～2 Ma normal faulting phase in the Tarim Basin represents a regional tensional tectonic stage which is a tectonic pause between 2 successive thrust pulses under the far-field effect of the India-Asia collision. -
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