Glacial advances constrained by 10Be exposure dating of bedrock landslides, Kyrgyz Tien Shan

Sanhueza-Pino, Katia, Korup, Oliver, Hetzel, Ralf, Munack, Henry, Weidinger, Johannes, Dunning, Stuart, Ormukov, Cholponbek and Kubik, Peter (2011) Glacial advances constrained by 10Be exposure dating of bedrock landslides, Kyrgyz Tien Shan. Quaternary Research, 76 (3). pp. 295-304. ISSN 0033-5894

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Numerous large landslide deposits occur in the Tien Shan, a tectonically active intraplate orogen in Central Asia. Yet their significance in Quaternary landscape evolution and natural hazard assessment remains unresolved due to the lack of "absolute" age constraints. Here we present the first 10Be exposure ages for three prominent (N107 m3) bedrock landslides that blocked major rivers and formed lakes, two of which subsequently breached, in the northern Kyrgyz Tien Shan. Three 10Be ages reveal that one landslide in the Alamyedin River occurred at 11–15 ka, which is consistent with two 14C ages of gastropod shells from reworked loess capping the landslide. One large landslide in Aksu River is among the oldest documented in semi-arid continental interiors, with a 10Be age of 63–67 ka. The Ukok River landslide deposit(s) yielded variable 10Be ages, which may result from multiple landslides, and inheritance of 10Be. Two 10Be ages of 8.2 and 5.9 ka suggest that one major landslide occurred in the early to mid-Holocene, followed by at least one other event between 1.5 and 0.4 ka. Judging from the regional glacial chronology, all three landslides have occurred between major regional glacial advances. Whereas Alamyedin and Ukok can be considered as postglacial in this context, Aksu is of interglacial age. None of the landslide deposits show traces of glacial erosion, hence their locations and 10Be ages mark maximum extents and minimum ages of glacial advances, respectively. Using toe to-headwall altitude ratios of 0.4–0.5, we reconstruct minimum equilibrium-line altitudes that exceed previous estimates by as much as 400 m along the moister northern fringe of the Tien Shan. Our data show that deposits from large landslides can provide valuable spatio temporal constraints for glacial advances in landscapes where moraines and glacial deposits have low preservation potential.

Item Type: Article
Uncontrolled Keywords: rock avalanche, 10Be exposure dating, quaternary glaciations, Tien Shan
Subjects: F600 Geology
F800 Physical and Terrestrial Geographical and Environmental Sciences
T400 Other Asian studies
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Helen Pattison
Date Deposited: 19 Apr 2012 14:10
Last Modified: 13 Oct 2019 00:31

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