Geomorphic evolution of glacier-fed Baspa Valley, NW Himalaya: record of Late Quaternary climate change, monsoon dynamics and glacial fluctuations
S. Dutta, S. A. I. Mujtaba, H. S. Saini, R. Chunchekar, P. Kumar, 2018. "Geomorphic evolution of glacier-fed Baspa Valley, NW Himalaya: record of Late Quaternary climate change, monsoon dynamics and glacial fluctuations", The Himalayan Cryosphere: Past and Present, N.C. Pant, R. Ravindra, D. Srivastava, L.G. Thompson
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In glacier-fed Baspa River valley, Late Quaternary climatic changes are archived in the terraces, fan and landslide deposits. An initial optically stimulated luminescence (OSL) based stratigraphy of these deposits is developed to deduce geomorphic evolution and palaeoclimatic changes. The data show large alluvial fan progradation around Sangla till c. 45 ka (middle of marine isotope stage 3 or MIS-3) due to glacial retreat and readjustment of glacigenic sediment under warm and humid conditions followed by incision. During the end phase of MIS-3 (>23 ka), intensified precipitation blocked the river course near Sangla and Kharogla by rock avalanches and imposed lacustrine conditions which recorded sedimentation until the beginning of Holocene (c. 11.4 ka). Reduced sedimentation in these lakes during the last glacial maximum (LGM) c. 23–18 ka suggests a cold and arid climate, whereas increased sedimentation during c. 18–11.5 ka indicates a warm and humid climate post-LGM. A palaeolake breach occurred during early Holocene and incision continued throughout the Holocene, with a pulse of fluvial aggradation during c. 9.1–6.5 ka over lacustrine remnant. In the upper reach of the valley (Chitkul area), coeval aggradation continued from >28 ka until c. 19 ka (MIS-3 to LGM) under cold and relatively arid conditions. This study emphasizes that Late Quaternary geomorphic evolution of Baspa valley is well synchronous with glacial fluctuations and the rapid response of the glacifluvial system to Indian summer monsoon (ISM) dynamics.
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The Himalaya mountains contain not only one of the largest concentrations of ice outside the polar regions, but contribute to the hydrological requirements of large populations spread over seven nations. The exceptionally high elevations of this low-latitude cryosphere presents a natural laboratory and archives to study climate–tectonics interactions as well as regional v. global climate influences. The existing base-level data on the Himalayan cryosphere are highly variable. Several climate fluctuations occurred during the late Quaternary (MIS1–MIS5, especially the last c. 100 ka), which led to the evolution of the Himalayan landscape. Detailed studies of these archives, along with those of the present cryosphere and related hydrosphere, are essential for understanding the controls on present and future hydrology of the glacial-fed mountain rivers.
This volume, a follow-up of the XII International Symposium on Antarctic Earth Science, Goa (A SCAR symposium), provides new data from locales spread over the entire Himalaya region and from Tibet. It provides a glimpse of the late Quaternary cryosphere, as well as a discussion in the last section on sustainability in the context of geohazard mitigations as well as the hydrological budget.