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Debris-flow-dependent variation of cosmogenically derived catchment-wide denudation rates

F. Kober, K. Hippe, B. Salcher, S. Ivy-Ochs, P. W. Kubik, L. Wacker and N. Haehlen
Debris-flow-dependent variation of cosmogenically derived catchment-wide denudation rates
Geology (Boulder) (August 2012) 40 (10): 935-938

Abstract

Catchment-wide denudation rates (CWDRs) obtained from cosmogenic nuclides are an efficient way to determine geomorphic processes quantitatively in alpine mountain ranges over Holocene time scales. These rate estimations assume steady geomorphic processes. Here we use a time series (3 yr) in the Aare catchment (central Swiss Alps) to test the impact of spatially heterogeneous stochastic sediment supply on CWDRs. Our results show that low-frequency, high-magnitude debris-flow events significantly perturb cosmogenic nuclide ( (super 10) Be, (super 14) C) concentrations and thus CWDRs. The (super 10) Be concentrations decrease by a factor of two following debris-flow events, resulting in a doubling of inferred CWDRs. The variability indicates a clear time and source dependency on sediment supply, with restricted area-weighted mixing of sediment. Accordingly, in transient environments, it is critical to have an understanding of the history of geomorphic processes to derive meaningful CWDRs. We hypothesize that the size of debris flows, their connectivity with the trunk stream, and the ability of the system to sufficiently mix sediment from low- and high-order catchments control the magnitude of CWDR perturbations. We also determined in situ (super 14) C in a few samples. In conjunction with (super 10) Be, these data suggest partial storage for colluvium of a few thousand years within the catchment prior to debris-flow initiation.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 40
Serial Issue: 10
Title: Debris-flow-dependent variation of cosmogenically derived catchment-wide denudation rates
Affiliation: Eidgenoessische Technische Hochschule Zuerich, Institute of Geology, Zurich, Switzerland
Pages: 935-938
Published: 20120801
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 20
Accession Number: 2012-075413
Categories: GeomorphologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2012263; accessed on August 6, 2012
Illustration Description: illus. incl. sketch map
Source Medium: WWW
N46°37'60" - N46°43'60", E08°00'00" - E08°25'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, 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: 201239
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