East-west extension in the NW Indian Himalaya
East-west extension in the NW Indian Himalaya
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DOI：
10.1130/b26589.1
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发表时间：
2010-09-01
影响因子：
4.9
通讯作者：
Hacker, Bradley R.
中科院分区：
文献类型：
--
作者：
Hintersberger, Esther;Thiede, Rasmus Ch.;Hacker, Bradley R.
在整体挤压背景下解释正断层的存在是理解活动造山带构造的一个具有挑战性的问题。喜马拉雅-青藏造山系统是研究这一问题的一个极好的背景，因为它保存了一个最引人注目的长期、同期缩短和伸展的记录。在过去的几十年里，一些研究描述了伸展特征，不仅在青藏高原，而且在喜马拉雅山。长期以来，有利的模型解释了藏南拆离系统的功能，喜马拉雅山的一个主要断裂带，作为地壳缩短机制之间的解耦层位形成喜马拉雅楔南部和青藏高原的伸展机制向北。然而，近年来，越来越多的证据表明，喜马拉雅山中部的南北向正断层不仅横切藏南拆离体系，而且横切中央主逆冲断层。我们提出了在印度西北部喜马拉雅山脉内收集的新的构造数据和地质证据，并将它们与以前公布的地震活动性数据集联合收割机结合起来，以便记录沿着N-S-向南延伸至主中央逆冲断层下盘的断层。我们进行了脆性断层上的断层条纹的运动学分析，记录和绘制断层陡崖在第四纪沉积矿床使用卫星图像，并在大Sutlej地区（Spiti，Lahul，Kinnaur）和Garhwal喜马拉雅山进行了实地观察。对区域性北西-南东向西北印度喜马拉雅伸展特征的研究提供了一个优势，即与喜马拉雅中部相比，平行弧形伸展和东西向伸展可以分开。因此，我们在印度西北部喜马拉雅山的东西延伸的观测非常适合于测试整个喜马拉雅山目前的构造模型的适用性。我们倾向于将印度喜马拉雅山西北部的东西向伸展解释为青藏高原崩塌驱动的伸展传播。
Explaining the presence of normal faults in overall compressive settings is a challenging problem in understanding the tectonics of active mountain belts. The Himalayan-Tibetan orogenic system is an excellent setting to approach this problem because it preserves one of the most dramatic records of long-term, contemporaneous shortening and extension. Over the past decades, several studies have described extensional features, not only in the Tibetan Plateau, but also in the Himalaya. For a long time, the favored model explained the function of the Southern Tibetan detachment system, a major fault zone in the Himalaya, as a decoupling horizon between the regime of crustal shortening forming the Himalayan wedge to the south and the extensional regime of the Tibetan Plateau to the north. However, in recent years, increasing evidence has shown that N-S-trending normal faults in the Central Himalaya crosscut not only the Southern Tibetan detachment system, but also the Main Central thrust.Here, we present new structural data and geologic evidence collected within the NW Indian Himalaya and combine them with previously published seismicity data sets in order to document pervasive E-W extension accommodated along N-S-trending faults extending as far south as the footwall of the Main Central thrust. We conducted a kinematic analysis of fault striations on brittle faults, documented and mapped fault scarps in Quaternary sedimentary deposits using satellite imagery, and made field observations in the Greater Sutlej region (Spiti, Lahul, Kinnaur) and the Garhwal Himalaya. Studies of extensional features within the regionally NW-SE-trending NW Indian Himalaya provide the advantage that arc-parallel and E-W extension can be separated, in contrast to the Central Himalaya. Therefore, our observations of E-W extension in the Indian NW Himalaya are well suited to test the applicability of current tectonic models for the whole Himalaya. We favor the interpretation of E-W extension in the NW Indian Himalaya as a propagation of extension driven by collapse of the Tibetan Plateau.