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- 저자 : Rahul Devrani (검색결과 2 건)
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Rahul Devrani,Vimal Singh,Hari S. Saini,Syed Ali I. Mujtaba 한국지질과학협의회 2023 Geosciences Journal Vol.27 No.1
The valley-fill deposits in a tectonically active setting play a key role in understanding a river’s response to climatic/tectonic shifts. These deposits are a result of the interaction between the regional and the local processes, which in turn are controlled by tectonics and climate. In this study, valley-fill deposits in the widest reach of the Alaknanda River (a headwater tributary of the Ganga River)—the Srinagar valley—in the northwest Himalaya is investigated for the interaction between, 1) the axial channel (representing regional processes) and local tributary (representing local processes) and 2) axial channel and hillslope (representing local processes). We identified eight levels of terraces and five levels of debris flow surfaces in the Srinagar valley. The terraces are composed of axial river deposits and local stream deposits, whereas debris flow surfaces mainly consist of hillslope deposits. Strath terraces are also present towards the western part of the valley. The 1D resistivity survey and field data show that thick sedimentary cover caps the bedrock in the eastern part of the Srinagar valley. Geochronology data based on optically stimulated luminescence (OSL) datingsuggests that some of the sediments in the Alaknanda valley are older than 80 ± 5 ka. Integration of results shows that the width of the Srinagar valley is controlled structurally by the presence of the North Almora Thrust (NAT), a regional structure present in the Alaknanda River basin. The valley width increases around the central part of the Srinagar valley; this increase in width has provided accommodation space and resulted in thick sedimentation. Major filling and evacuation of the Srinagar valley occurred between 80 ± 5 ka and 8 ± 1 ka. The study demonstrates that the long-term interaction of the axial river, tributaries, and the hillslope processes can often be masked by the younger sediments to give a deceptive morphology and evolution history, if not thoroughly investigated.
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Manish Mehta,Rahul Devrani,Khayingshing Luirei,Vinit Kumar 한국지질과학협의회 2022 Geosciences Journal Vol.26 No.2
In the present study, we are reporting an unnamed glacier located (30.28089N- 80.69344E) in the upper Kali Ganga valley, Pithoragarh district, Uttarakhand, India, which has been affected by active fault and climate change. Recent tectonic activity and change in climatic conditions have changed the course and morphology of this glacier. An active fault has produced a fault scarp that measures about 250 m in height with a northerly dip, the fault trace is 6.2 km in length and trend towards NW-SE. The observation is based on the satellite image, toposheet and Google Earth images. We observed that the 5 km long unnamed glacier, which covered ~4 km2 area in Kuthi Yankti valley (Tributary of Kali River) has abruptly changed its main course. The NE moving glacier has been abruptly truncated and forced to move towards SE and ultimately merges with the adjacent glacier named Sumzurkchanki as a result of tectonic forcing. It is one of the unique behaviors of the glacier, which is for the first time reported from the Himalayan glacier as no such observation have so far been reported on this type of glacier kinematics. The study will help to understand the glacial-tectonic interaction and provides key information for future studies.
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