School Of Environment And Earth Sciences
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Item Luminescence chronology of alluvial fan in North Bengal, India: Implications to tectonics and climate(Walter de Gruyter GmbH, 2016) Singh, A.K.; Jaiswal, M.K.; Pattanaik, J.K.; Dev, M.Alluvial fans are important geomorphic archives because of its strategic location at mountain front which can provide clues to the past climate and tectonics. In general, they provide information about optimum climate condition suitable for fan formation. We provide a detailed luminescence chronology of alluvial fan in north West Bengal, India. The regional fan surface (T44) has been dissected by E-W trending Himalayan thrusts known as Matiali and Chalsa thrusts and have various terraces named as T3, T2 and youngest one as T1. Luminescence ages suggest that the formation of the alluvial fan (regional surface) started before 171 ka and continued till 72 ka covering a time span of nearly 100 ky; suggesting of weaker monsoon at 72 ka. Matiali fault activated after 171 ky. Chalsa fault is suggested to be active during 48-41 ka. The last aggradational phase was around 6 ka which led to the formation of T1a terrace. The study suggests that climatic fluctuation during the period were shaping the morphology of the alluvial fan, along with tectonic activities on the two faults. ? 2015 A. K. Singh et al.Item Late Quaternary evolution of Tista River terraces in Darjeeling-Sikkim-Tibet wedge: Implications to climate and tectonics(Elsevier Ltd, 2017) Singh, A.K.; Pattanaik, J.K.; Gagan, Jaiswal, M.K.Terraces in the Himalayas are important geomorphic archives which preserve the signature of tectonics and past environment. Terraces in eastern part of the Himalayan fold and thrust belt have not received much attention of the geologists. A geochemical approach using luminescence dating has been applied to understand the evolution of paired and deformed terraces between major thrust boundaries of the eastern Himalayas, on the either banks of the Tista River in Darjeeling-Sikkim-Tibet wedge. These terraces are located at the confluence of Tum Thang khola and the Tista River. Three levels of terraces are present in general and also in the study area. The terrace T3 was formed during last interglacial period and the T2 terrace during last glacial maximum (LGM) and in the humid phases after LGM. The top section of T2 terrace (?2.5 m thick) was formed in the transition phase (arid to humid) after Younger Dryas event. The region has experienced several deformational events, (i) one after 45 ka which raised the T3 terrace to its present level, (ii) another one after 11.9 ka which raised the T2 to its present level and this event is also associated with the shifting of the Tum Thang khola, and (iii) the region is still tectonically active as shown by the warping of the T1 and T0 surfaces, which are of recent origin. These terraces have complex input of sediments from Higher Himalayan Crystalline (HHC) rocks and from locally present Lingtse granites. ? 2016 Elsevier Ltd and INQUA