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Contrasting river incision in north and south Tian Shan piedmonts due to variable glacial imprint in mountain valleys

Malatesta, Luca C. and Avouac, Jean-Philippe (2018) Contrasting river incision in north and south Tian Shan piedmonts due to variable glacial imprint in mountain valleys. Geology, 46 (7). pp. 659-662. ISSN 0091-7613. http://resolver.caltech.edu/CaltechAUTHORS:20180612-083811607

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Abstract

Fluvial terraces carved by incising rivers are widely used to investigate external forcing by climate and tectonics. In the Eastern Tian Shan (Central Asia), the north piedmont rivers are much more deeply incised (mean: 124 m) compared to the south piedmont (mean: 17 m) despite very similar tectonic and climatic settings. We attribute the incision contrast to a difference in glacial imprint between southern and northern catchments. Whereas the upper halves of the valleys in the northern higher subrange are formerly glaciated, wide and gently sloping, U-shaped valleys flowing into V-shaped valleys, the valleys of the lower southern subrange are entirely V-shaped. The glacially widened valleys act as capacitors that accumulate and release glacial and periglacial sediment onto the piedmont. The resulting discrete pulse in sediment flux, Q_s, forces aggradation and steepening, followed by incision and gentler slopes of the piedmont rivers. The fluvial valleys do not accumulate sediment, and changes in water discharge primarily control the slope of the piedmont rivers. Today, incision in the north is associated with the drop in Q_s that occurred after depletion of the upstream reservoir, while aggradation in the south is due to Central Asian aridity. The same climatic forcing can have strikingly distinct morphological expressions downstream of catchments with different glacial imprints.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1130/G40320.1DOIArticle
ORCID:
AuthorORCID
Avouac, Jean-Philippe0000-0002-3060-8442
Additional Information:© 2018 Geological Society of America. Manuscript received 25 March 2018; Revised manuscript received 17 May 2018; Manuscript accepted 6 June 2018. This study was supported by a Petroleum Research Fund (PRF) New Direction grant of the American Chemical Society (grant PRF #53814-ND8) and a Doc. Mobility fellowship of the Swiss National Foundation (project P1SKP2_158716) to Malatesta. We thank R. Heermance for insightful comments and his suggestion to test the model in the Northwest Tian Shan, We also thank L. Guerit, Guangwei Li, and two anonymous reviewers.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
American Chemical Society Petroleum Research Fund53814-ND8
Swiss National Science Foundation (SNSF)P1SKP2_158716
Record Number:CaltechAUTHORS:20180612-083811607
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180612-083811607
Official Citation:Luca C. Malatesta, Jean-Philippe Avouac; Contrasting river incision in north and south Tian Shan piedmonts due to variable glacial imprint in mountain valleys. Geology ; 46 (7): 659–662. doi: https://doi.org/10.1130/G40320.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86988
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Jun 2018 16:18
Last Modified:05 Jul 2018 20:38

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