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Evidence for late Quaternary brittle deformation and back thrusting within the Indus Suture Zone, Ladakh Himalaya
Tectonophysics ( IF 2.9 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.tecto.2020.228597
Anil Kumar , Pradeep Srivastava , Koushik Sen , Kristin Morell , Devajit Hazarika

Abstract Although the tectonic evolution of the southern Himalaya has been extensively studied, relatively few studies have focused on potential neotectonic activity in the most hinterland part of Himalaya, north of the region that separates the southern edge of the Tibetan plateau from the peaks of the Higher Himalayan Range. Here we use a combination of new structural and geomorphic field data, Optically Stimulated Luminescence (OSL) chronology, as well as previously published seismicity and denudation rate dataset, to suggest that the Trans-Himalaya within the region of the Indus Suture Zone (ISZ) is neotectonically active. Based on fault gouge, tilted paleolake deposits, and the chronology of deformed fluvial gravels constrained by OSL dating, the present study provides evidence for the tectonic activity along the ISZ between 78 and 58 ka. The occurrence of two earthquakes of Mw ≥ 4.0 and the focal mechanism solution of a shallow focus earthquake (Mw: 3.0, depth ~ 8 km) near the town of Upshi, shows a pure thrust mechanism. We suggest that this earthquake was likely associated with the Upshi-Bazgo thrust, a major structure which separates the mid-Miocene Indus Molasse from the Cretaceous Ladakh Batholith. It is envisaged that the fault and fold systems in the Ladakh region such as the Upshi-Bazgo thrust originated due to (1) acceleration in the northward movement of Indian plate relative to the Eurasian plate, and (2) post-collisional shortening parallel to plate convergence. On account of this, the Eocene to Miocene post-collisional sedimentary sequences, such as the Indus Molasse, rode over the now-extinct Ladakh Arc, as it acted as a rigid body, and formed a system of backthrusts, which are neotectonically active.

中文翻译:

拉达克喜马拉雅印度河缝合带内晚第四纪脆性变形和反冲的证据

摘要 尽管对喜马拉雅南部的构造演化进行了广泛的研究,但相对较少的研究集中于喜马拉雅最腹地部分的潜在新构造活动,该地区位于将青藏高原南缘与高山峰区分开的地区以北。喜马拉雅山脉。在这里,我们结合使用新的构造和地貌场数据、光激发光 (OSL) 年代学以及先前发布的地震活动和剥蚀率数据集,来表明印度河缝合带 (ISZ) 区域内的跨喜马拉雅山脉是新构造活动的。基于断层泥、倾斜古湖沉积物和受 OSL 定年约束的变形河流砾石年代学,本研究为 78 至 58 ka 之间沿 ISZ 的构造活动提供了证据。乌普施镇附近发生了两次 Mw ≥ 4.0 地震和一次浅源地震(Mw:3.0,深度~8 km)的震源机制解,显示出纯逆冲机制。我们认为这次地震可能与 Upshi-Bazgo 逆冲断层有关,这是一个将中新世印度河磨拉石与白垩纪拉达克岩基分开的主要结构。据推测,拉达克地区的断层和褶皱系统,例如 Upshi-Bazgo 逆冲断层,起源于(1)印度板块相对于欧亚板块向北运动的加速,以及(2)碰撞后平行于欧亚板块的缩短。板块收敛。有鉴于此,始新世至中新世碰撞后沉积序列,如印度河磨拉砂,骑在现已灭绝的拉达克弧上,因为它作为一个刚体,
更新日期:2020-10-01
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