Provenance Shifts During Neogene Brahmaputra Delta Progradation Tied to Coupled Climate and Tectonic Change in the Eastern Himalaya
Provenance Shifts During Neogene Brahmaputra Delta Progradation Tied to Coupled Climate and Tectonic Change in the Eastern Himalaya
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DOI：
10.1029/2021gc010026
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发表时间：
2021-11
期刊：
影响因子：
3.7
通讯作者：
P. Betka;S. Thomson;R. Sincavage;C. Zoramthara;C. Lalremruatfela;K. Lang;M. Steckler;D. Bezbaruah;P. Borgohain;L. Seeber
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作者：
P. Betka;S. Thomson;R. Sincavage;C. Zoramthara;C. Lalremruatfela;K. Lang;M. Steckler;D. Bezbaruah;P. Borgohain;L. Seeber
孟加拉盆地保存了喜马拉雅造山带晚新生代发展过程中耦合构造-气候变化的侵蚀信号，但这些信号的区域对比和解释仍然不完整。我们提出了一个新的地质图的河流-三角洲沉积的印度-缅甸山脉（IBR），5个碎屑锆石裂变径迹分析，和12个高氮碎屑锆石U-Pb年龄分布（dzUPb）从Barail（晚始新世-早中新世），Surma（早中新世-晚中新世），和Tipam（晚中新世-上新世）组的祖先雅鲁藏布江三角洲。我们使用dzUPb统计检验相关的IBR单位与整个孟加拉盆地的等效年龄层。跨喜马拉雅沉积物的流入和下苏尔马群（18 Ma-15 Ma）中冈底斯岩基的150 Ma颗粒的首次出现记录了原始雅鲁藏布江三角洲到孟加拉盆地的早中新世到达。随着跨喜马拉雅弧源的贡献增加，喜马拉雅源的贡献在整个中新世晚期系统地减少。苏尔玛群的中新世（距今18-8 Ma）沉积记录了古老的雅鲁藏布江向西藏东南部的上游扩张。晚中新世（<8 Ma）三角洲（Tipam群）河流部分的扩张将喜马拉雅山脉沉积物穿过陆架边缘到达尼科巴扇。我们建议，中新世的祖先雅鲁藏布江三角洲的侵蚀反映了增加的侵蚀率和海平面下降的南亚季风加强后，中新世气候最佳，同时与喜马拉雅腹地和西藏的构造隆起的脉冲。
The Bengal Basin preserves the erosional signals of coupled tectonic‐climatic change during late Cenozoic development of the Himalayan orogen, yet regional correlation and interpretation of these signals remains incomplete. We present a new geologic map of fluvial‐deltaic deposits of the Indo‐Burman Ranges (IBR), five detrital zircon fission track analyses, and twelve high‐n detrital zircon U‐Pb age distributions (dzUPb) from the Barail (late Eocene–early Miocene), Surma (early–late Miocene), and Tipam (late Miocene–Pliocene) Groups of the ancestral Brahmaputra delta. We use dzUPb statistical tests to correlate the IBR units with equivalent age strata throughout the Bengal Basin. An influx of trans‐Himalayan sediment and the first appearance of ∼50 Ma grains of the Gangdese batholith in the lower Surma Group (∼18–15 Ma) records the early Miocene arrival of the ancestral Brahmaputra delta to the Bengal Basin. Contributions from Himalayan sources systematically decrease up section through the late Miocene as the contribution of Trans‐Himalayan Arc sources increases. The Miocene (∼18–8 Ma) deposition of the Surma Group records upstream expansion of the ancestral Brahmaputra River into southeastern Tibet. Late Miocene (<8 Ma) progradation of the fluvial part of the delta (Tipam Group) routed trans‐Himalayan sediment over the shelf edge to the Nicobar Fan. We propose that Miocene progradation of the ancestral Brahmaputra delta reflects increasing rates of erosion and sea level fall during intensification of the South Asian Monsoon after the Miocene Climate Optimum, contemporaneous with a pulse of tectonic uplift of the Himalayan hinterland and Tibet.