Formation and breaching of two palaeolakes around Leh, Indus valley, during the late Quaternary
S. A. I. Mujtaba, Ravish Lal, H. S. Saini, Pawan Kumar, N. C. Pant, 2018. "Formation and breaching of two palaeolakes around Leh, Indus valley, during the late Quaternary", The Himalayan Cryosphere: Past and Present, N.C. Pant, R. Ravindra, D. Srivastava, L.G. Thompson
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Of the several types of Quaternary deposits formed by glacial, alluvial and mass-wasting processes, with vast climatic and tectonic significance lake deposits stand out prominently in the Indus valley around the town of Leh. We studied a number of palaeolake deposits between the Zinchan–Indus confluence and Shey village and carried out optically stimulated luminescence (OSL) quartz dating of samples from critical sections. Our results indicate that, during the late Quaternary, the Indus River was dammed at least twice in the narrow gorge downstream of Spituk Gompa, forming a reservoir up to 35 km long in which 20–68 m thick sediments were deposited under fluvial and lacustrine environments. During the older phase, the Indus was blocked by debris of moraines/landslides in the narrow zone near the Zinchan–Indus confluence. The resulting lake existed between c. 125 ± 11 and 87 ± 8 ka during marine isotopic stage (MIS) 5. No evidence of damming material is preserved. Present-day elevations of lake deposits suggest a possible extension of the lake up to Ranbirpura upstream. After the lake breach, the Indus River was again dammed near Phey village by the advancing alluvial fan of the Phyang River. This lake, extending up to Karu, formed at c. 79 ± ka. The lake existed in this phase during c. 72–49 ka, during cold-stage MIS-4. The lake was breached after c. 46 ± 3 ka, however.
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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.