The Brahmaputra tale of tectonics and erosion: Early Miocene river capture in the Eastern Himalaya
The Brahmaputra tale of tectonics and erosion: Early Miocene river capture in the Eastern Himalaya
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雅鲁藏布江的构造与侵蚀故事：喜马拉雅东部早中新世的河流袭夺
DOI：
10.1016/j.epsl.2015.01.022
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发表时间：
2015-04-01
影响因子：
5.3
通讯作者：
Millar, Ian
中科院分区：
文献类型：
--
作者：
Bracciali, Laura;Najman, Yani;Millar, Ian
喜马拉雅造山带提供了一个典型的例子，许多地壳变形的原因和后果的模型都是以此为基础的，有人认为它是构造和侵蚀之间各种反馈的场所。在更广泛的造山带内，河流流域部分反映了地表抬升、不同的气候带和对地壳变形的响应。在喜马拉雅东部，雅鲁藏布江-雅鲁藏布江不寻常的排水形态被解释为被印度-亚洲碰撞扭曲的先行排水(并因此被用作侧向挤压的被动应变标志)、新近纪构造诱导的河流捕获或冰川筑坝诱导的河流分流事件。在这里，我们应用多种技术方法对苏尔玛盆地(孟加拉国孟加拉盆地)的新近纪古雅鲁藏布江沉积进行测试，以检验雅鲁藏布江被雅鲁藏布江夺取河流的长期争论的发生和时间。我们提供了与雅鲁藏布江在中新世早期捕获雅鲁藏布江一致的U-Pb碎屑锆石和金红石、同位素(锶-ND和Hf)和岩石学证据。我们记录了白垩纪-古近纪锆石在古雅鲁藏布江早中新世沉积中的流入，我们将其解释为来自亚洲板块(跨希玛拉雅弧)的第一次物质流入，表明雅鲁藏布江的贡献。在捕获之前，以前寒武纪-古生代为主的锆石表明，只有印度板块被排干。与反映河流捕获的陆相马拉雅侵入同时，我们记录了受新生代变质作用影响的碎屑物质的到来，如金红石和锆石的新生代U-Pb年龄，以及岩相学记录的碎屑变质程度的增加。我们认为这是由于造山带变质核的侵蚀作用逐渐增加所致。同一样品的全岩锶-钕同位素数据进一步支持了这一解释。河流捕获可能是由于青藏高原隆升导致相对基准面的变化造成的。假设这种河流捕获发生在中新世早期，我们驳斥了河流捕获和东部构造快速折返之间的构造侵蚀耦合的“构造动脉瘤”模型，因为现在证明了这两个事件之间至少有10 Ma的时间间隔。这项工作也是首次强调碎屑金红石U-铅年龄是研究喜马拉雅物源的有力手段，并与锆石U-铅年代学相结合。(C)2015爱思唯尔B.V.保留所有权利。
The Himalayan orogen provides a type example on which a number of models of the causes and consequences of crustal deformation are based and it has been suggested that it is the site of a variety of feedbacks between tectonics and erosion. Within the broader orogen, fluvial drainages partly reflect surface uplift, different climatic zones and a response to crustal deformation. In the eastern Himalaya, the unusual drainage configuration of the Yarlung Tsangpo-Brahmaputra River has been interpreted either as antecedent drainage distorted by the India-Asia collision (and as such applied as a passive strain marker of lateral extrusion), latest Neogene tectonically-induced river capture, or glacial damming-induced river diversion events.Here we apply a multi-technique approach to the Neogene paleo-Brahmaputra deposits of the Surma Basin (Bengal Basin, Bangladesh) to test the long-debated occurrence and timing of river capture of the Yarlung Tsangpo by the Brahmaputra River. We provide U-Pb detrital zircon and rutile, isotopic (Sr-Nd and Hf) and petrographic evidence consistent with river capture of the Yarlung Tsangpo by the Brahmaputra River in the Early Miocene. We document influx of Cretaceous-Paleogene zircons in Early Miocene sediments of the paleo-Brahmaputra River that we interpret as first influx of material from the Asian plate (Transhimalayan arc) indicative of Yarlung Tsangpo contribution. Prior to capture, the predominantly Precambrian-Paleozoic zircons indicate that only the Indian plate was drained. Contemporaneous with Transhimalayan influx reflecting the river capture, we record arrival of detrital material affected by Cenozoic metamorphism, as indicated by rutiles and zircons with Cenozoic U-Pb ages and an increase in metamorphic grade of detritus as recorded by petrography. We interpret this as due to a progressively increasing contribution from the erosion of the metamorphosed core of the orogen. Whole rock Sr-Nd isotopic data from the same samples provide further support to this interpretation. River capture may have been caused by a change in relative base level due to uplift of the Tibetan plateau. Assuming such river capture occurred via the Siang River in the Early Miocene, we refute the "tectonic aneurysm" model of tectonic-erosion coupling between river capture and rapid exhumation of the eastern syntaxis, since a time interval of at least 10 Ma between these two events is now demonstrated. This work is also the first to highlight U-Pb dating on detrital rutile as a powerful approach in provenance studies in the Himalaya in combination with zircon U-Pb chronology. (C) 2015 Elsevier B.V. All rights reserved.