Pleistocene rapid uplift of the Himalayan frontal ranges recorded in the Kathmandu and Siwalik basins
Pleistocene rapid uplift of the Himalayan frontal ranges recorded in the Kathmandu and Siwalik basins
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DOI：
10.1016/j.palaeo.2006.06.017
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发表时间：
2006-11
期刊：
影响因子：
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通讯作者：
H. Sakai;H. Sakai;Wataru Yahagi;R. Fujii;Tatsuya Hayashi;B. Upreti
中科院分区：
文献类型：
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作者：
H. Sakai;H. Sakai;Wataru Yahagi;R. Fujii;Tatsuya Hayashi;B. Upreti
在加德满都盆地南缘进行的岩心钻探项目显示，在 1.07 Ma 至 0.97 Ma 的 Jaramillo 亚纪元期间，泥石流沉积物堵塞了 Proto-Bagmati 河，形成了古加德满都湖。随后，来自南部摩诃婆罗多山脉隆起的冲积尖岩沉积，抬高了水坝，加深了湖水。 1 Ma之后，在盆地南部，古水流方向由南转为北，片麻岩和花岗岩碎屑的沉积被来自摩诃婆罗多山脉的变质沉积物所取代。与此同时，大约在 1 Ma 时，沿着尼泊尔和印度西北部的主要粪冲断层，巨石砾岩沉积在西瓦利克群的顶部，作为盆内高点前面的背负盆地。主要粪便逆冲运动的开始可追溯到 3 至 2.4 Ma [Mugnier, J.L., Huyge, P., Leturmy, P., Jouanne, F., 2003, 尼泊尔西部喜马拉雅山逆冲层运动的情景性和速率。是。副教授。汽油。地质学家，内存。 82，1-24]。目前，主额逆冲断层最为活跃，表明西瓦利克群的叠瓦状结构是由印度板块在过去 3 英里的聚合过程中形成的。堆积在主边界冲断层下方的西瓦利克群的增生楔可能自 1 Ma 起就开始抬升小喜马拉雅山的锋面范围。自 1 Ma 以来，小喜马拉雅山锋区和西瓦利克盆地内高压的同时期抬升和侵蚀可能是导致 0.9 Ma 孟加拉深海扇沉积物中碎屑石英沉积速率和粒度突然增加以及粘土矿物成分变化的原因。
Core-drilling project carried out in the southern margin of the Kathmandu Basin revealed that muddy debris flow deposits dammed up the Proto-Bagmati river to form the Paleo-Kathmandu Lake during the Jaramillo subchron from 1.07 to 0.97 Ma. Subsequent deposition of the alluvial fanglomerate, derived from the uplifting Mahabharat Range to the south, raised the dam deepening the lake-water. After 1 Ma, in the southern part of the basin, palaeo-current directions changed from southward to northward and deposition of gneissose and granitic detritus are replaced by meta-sediments derived from the Mahabharat Range. During the same time, at about 1 Ma, the boulder conglomerates were deposited on top of the Siwalik Group as piggy-back basins in front of an intra-basinal high, along the Main Dung Thrust in Nepal and NW India. Onset of movement of the Main Dung Thrust is dated back to 3 to 2.4 Ma [Mugnier, J.L., Huyge, P., Leturmy, P., Jouanne, F., 2003, Episodicity and rates of thrust-sheet motion in the Himalayas, Western Nepal. Am. Assoc. Petrol. Geol., Mem. 82, 1–24]. The Main Frontal Thrust is most active at present suggesting that imbricated structure of the Siwalik Group was formed by convergence of the Indian plate during the last 3 myr. The accretionary wedge of the Siwalik Group, stacked beneath the Main Boundary Thrust, might have started to jack up the frontal range of the Lesser Himalaya since 1 Ma. Coeval uplift and erosion of the frontal range of the Lesser Himalaya and the intra-basinal high in the Siwalik since 1 Ma are possible causes of an abrupt increase in both sedimentation rate and grain size of detrital quartz, and changes in composition of clay minerals, recorded in the sediments of the Bengal Deep Sea Fan at 0.9 Ma.