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Impulsive alluviation during early Holocene strengthened monsoons, central Nepal Himalaya

2002; Geological Society of America; Volume: 30; Issue: 10 Linguagem: Inglês

10.1130/0091-7613(2002)030 2.0.co;2

1943-2682

B. A. Pratt, Douglas W. Burbank, Arjun M. Heimsath, T. P. Ojha,

Geological formations and processes

Research Article| October 01, 2002 Impulsive alluviation during early Holocene strengthened monsoons, central Nepal Himalaya Beth Pratt; Beth Pratt 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA Search for other works by this author on: GSW Google Scholar Douglas W. Burbank; Douglas W. Burbank 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA Search for other works by this author on: GSW Google Scholar Arjun Heimsath; Arjun Heimsath 2Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Search for other works by this author on: GSW Google Scholar Tank Ojha Tank Ojha 3Himalayan Experience, P.O. Box 5674, Kathmandu, Nepal Search for other works by this author on: GSW Google Scholar Author and Article Information Beth Pratt 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA Douglas W. Burbank 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA Arjun Heimsath 2Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Tank Ojha 3Himalayan Experience, P.O. Box 5674, Kathmandu, Nepal Publisher: Geological Society of America Received: 02 Jan 2002 Revision Received: 12 Jun 2002 Accepted: 19 Jun 2002 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2002) 30 (10): 911–914. https://doi.org/10.1130/0091-7613(2002)030 2.0.CO;2 Article history Received: 02 Jan 2002 Revision Received: 12 Jun 2002 Accepted: 19 Jun 2002 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Beth Pratt, Douglas W. Burbank, Arjun Heimsath, Tank Ojha; Impulsive alluviation during early Holocene strengthened monsoons, central Nepal Himalaya. Geology 2002;; 30 (10): 911–914. doi: https://doi.org/10.1130/0091-7613(2002)030 2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The steep-walled bedrock gorges of the Greater Himalayan rivers currently lack significant stored sediment, suggesting that fluvial erosion and transport capacity outpace the supply of sediment from adjacent hillsides. Despite this appearance of sustained downcutting, such rivers can become choked with sediments and aggrade during intervals of higher precipitation. Cosmogenic dating (10Be and 26Al) of fluvially carved bedrock surfaces indicates that sediment at least 80 m thick filled the Marsyandi River valley in central Nepal during a time of strengthened early Holocene monsoons. Despite threefold differences in height (43–124 m) above the modern river, these fluvial surfaces display strikingly similar cosmogenic exposure ages clustering around 7 ± 1 ka. We speculate that enhanced monsoonal precipitation increased pore pressure and the frequency of landsliding, thereby generating a pulse of hillslope-derived sediment that temporarily overwhelmed this alpine fluvial system's transport capacity. After the easily liberated material was exhausted ca. 7 ka, the hillslope flux dropped, and the river incised through the aggraded alluvium. It concurrently eroded adjacent rock walls, thereby removing previously accumulated 10Be and 26Al and resetting the cosmogenic clock in the bedrock. Unlike previous studies, these exposure ages cannot be used to derive river-incision rates; instead they record a coupled fluvial-hillslope response to climate change. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.