Multiproxy Isotopic and Geochemical Analysis of the Siwalik Sediments in NW India: Implication for the Late Cenozoic Tectonic Evolution of the Himalaya
Multiproxy Isotopic and Geochemical Analysis of the Siwalik Sediments in NW India: Implication for the Late Cenozoic Tectonic Evolution of the Himalaya
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DOI：
10.1029/2018tc005200
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发表时间：
2018-11
期刊：
影响因子：
4.2
通讯作者：
S. Mandal;D. Scherler;R. Romer;J. Burg;M. Guillong;A. Schleicher
中科院分区：
文献类型：
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作者：
S. Mandal;D. Scherler;R. Romer;J. Burg;M. Guillong;A. Schleicher
对Dehradun再入地区晚中新世-更新世亚喜马拉雅前陆盆地沉积（siwalik）的物源分析提供了印度喜马拉雅西北部长达10 - Myr的剥蚀历史和构造演化记录。我们利用碎屑锆石U - Pb年代学、主微量元素和Sr - Nd同位素地球化学研究了Mohand - Rao和Haripur - Khol剖面暴露的Siwalik沉积物。结果表明，自晚中新世以来，侵蚀模式相对稳定，沉积物来自特提斯喜马拉雅（THS）、大喜马拉雅（GHS）、外喜马拉雅（oLHS）和内喜马拉雅（iLHS）序列。物源资料表明，小喜马拉雅结晶层序（LHCS）的侵蚀剥落始于6 Ma左右，可能与Ramgarh - Munsiari逆冲的层序外运动有关。我们的数据还表明，自~5.5 Ma以来，较老的前陆盆地沉积在较年轻的Siwaliks中发生了侵蚀再循环，这可能表明了从小喜马拉雅到前陆盆地的冲断传播时间。虽然iLHS暴露于侵蚀至少约10 Ma，但siwalik主要是来自GHS和THS来源的物质。我们将这些结果解释为构造隆起和造山带的侵蚀是对大喜马拉雅和特提斯喜马拉雅地区iLHS和伴随的高地形和岩石隆升率的双重反应。将siwalick沉积物的物源与现代恒河和亚穆纳河沉积物的物源进行比较，进一步表明晚新生代的沉积很可能是由喜马拉雅横向河流南下完成的，与现代相似。
Provenance analysis of the Sub‐Himalayan Late Miocene‐Pleistocene foreland basin deposits (Siwaliks) from the Dehradun reentrant area provides a 10‐Myr long record of the denudation history and tectonic evolution of the northwestern Indian Himalaya. We studied Siwalik sediments exposed along the Mohand‐Rao and Haripur‐Khol sections, using detrital zircon U‐Pb geochronology, major and trace elements, and Sr‐Nd isotope geochemistry. Results suggest that the erosion pattern has been relatively stable since the Late Miocene with sediments derived from the Tethyan Himalayan (THS), Greater Himalayan (GHS), and outer‐ (oLHS) and inner‐Lesser Himalayan (iLHS) sequences. Provenance data indicate that erosional unroofing of the Lesser Himalayan Crystalline sequences (LHCS) initiated around 6 Ma, possibly related to out‐of‐sequence movement of the Ramgarh‐Munsiari Thrust. Our data also suggest erosional recycling of older foreland basin deposits into younger Siwaliks since ~5.5 Ma, which may indicate the time of thrust propagation from the Lesser Himalaya into the foreland basin. While the iLHS has been exposed to erosion since at least ~10 Ma, the Siwaliks were dominated by materials derived from the GHS and THS sources. We interpret these results as an indication that tectonic uplift and erosion of the orogenic wedge occurred in response to duplexing of the iLHS and concomitant high topography and rock uplift rate in the Greater and Tethyan Himalaya. Comparing the provenance of the Siwalik sediments with that of the modern Ganga and Yamuna river sediments further indicates that deposition during the Late Cenozoic was most likely accomplished by southward flowing transverse Himalayan rivers, analogous to the modern ones.