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Ice dams, outburst floods, and glacial incision at the western margin of the Tibetan Plateau; a >100 k.y. chronology from the Shyok Valley, Karakoram

Dirk Scherler, Henry Munack, Juergen Mey, Patricia Eugster, Hella Wittmann, Alexandru T. Codilean, Peter Kubik and Manfred R. Strecker
Ice dams, outburst floods, and glacial incision at the western margin of the Tibetan Plateau; a >100 k.y. chronology from the Shyok Valley, Karakoram
Geological Society of America Bulletin (February 2014) 126 (5-6): 738-758

Abstract

Some of the largest and most erosive floods on Earth result from the failure of glacial dams. While potentially cataclysmic ice dams are recognized to have repeatedly formed along ice-sheet margins, much less is known about the frequency and longevity of ice dams caused by mountain glaciers, and their impact on landscape evolution. Here we present field observations and results from cosmogenic nuclide dating that allow reconstructing a >100-k.y.-long history of glacial damming in the Shyok Valley, eastern Karakoram (South Asia). Our field observations provide evidence that Asia's second-longest glacier, the Siachen, once extended for over 180 km and blocked the Shyok River during the penultimate glacial period, leading to upstream deposition of a more than 400-m-thick fluvio-lacustrine valley fill. (super 10) Be-depth profile modeling indicates that glacial damming ended with the onset of the Eemian interglacial and that the Shyok River subsequently incised the valley fill at an average rate of approximately 4-7 m k.y. (super -1) . Comparison with contemporary ice-dammed lakes in the Karakoram and elsewhere suggests recurring outburst floods during the aggradation period, while over 25 cycles of fining-upward lake deposits within the valley fill indicate impounding of floods from farther upstream. Despite prolonged damming, the net effect of this and probably earlier damming episodes by the Siachen Glacier is dominated by glacial erosion in excess of fluvial incision, as evidenced by a pronounced overdeepening that follows the glaciated valley reach. Strikingly similar overdeepened valleys at all major confluences of the Shyok and Indus Rivers with Karakoram tributaries indicate that glacial dams and subsequent outburst floods have been widespread and frequent in this region during the Quaternary. Our study suggests that the interaction of Karakoram glaciers with the Shyok and Indus Rivers promoted valley incision and headward erosion into the western margin of the Tibetan Plateau.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 126
Serial Issue: 5-6
Title: Ice dams, outburst floods, and glacial incision at the western margin of the Tibetan Plateau; a >100 k.y. chronology from the Shyok Valley, Karakoram
Affiliation: University of Potsdam, Institute of Earth and Environmental Sciences, Potsdam, Germany
Pages: 738-758
Published: 20140213
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 105
Accession Number: 2014-014783
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2014082
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N34°30'00" - N34°30'00", E77°30'00" - E77°30'00"
Secondary Affiliation: Deutsches GeoForschungsZentrum, DEU, GermanyEidgenoessische Technische Hochschule Zuerich,
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201410
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