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Eroding the land; steady-state and stochastic rates and processes through a cosmogenic lens

Arjun M. Heimsath
Eroding the land; steady-state and stochastic rates and processes through a cosmogenic lens (in In situ-produced cosmogenic nuclides and quantification of geological processes, Lionel L. Siame (editor), Didier L. Bourles (editor) and Erik T. Brown (editor))
Special Paper - Geological Society of America (2006) 415: 111-129


Quantifying erosion rates and processes remains a central focus of studying the Earth's surface. Measurement of in situ-produced cosmogenic radionuclides (CRNs) enables a level of quantification that would otherwise be impossible or fraught with uncertainty and expense. Remarkable success stories punctuate the field over the last decade as CRN-based methodologies are pushed to new limits. Inherent to all is an assumption of steady-state rates and processes. This paper focuses on the use of cosmogenic (super 10) Be and (super 26) Al, extracted from quartz in bedrock, saprolite, and detrital material to quantify sediment production or erosion rates and processes. Previous results from two very different field areas are reviewed to highlight the potential for non-steady-state processes in shaping soil-mantled landscapes. With this potential in mind, a numerical model is presented, following a review of the CRN conceptual framework, to test the effects of non-steady-state erosion rates and processes on CRN concentrations. Results from this model focus on (super 10) Be concentrations accumulated under modeled variations in erosion rates with different ranges, frequencies, and styles of variability. In general, the higher the maximum erosion rate, the higher the impact on the CRN concentration and, therefore, the more likely that point measurements will capture the variable signal. Conversely, the higher the frequency of erosional variation, the less likely point measures are to accurately determine rates, but the closer the inferred rate is to the mean of the long-term erosion rate. Modeling results are applicable for point-specific erosion rates, but endorse the catchment-averaged approach for determining average rates. Potentially large uncertainties emphasize the need for careful sample selection, with adequate numbers of samples collected for quantifying the processes eroding the land. The two field examples show how analyzing enough samples can define a clear soil production function despite the potential for non-steady-state processes. The model presented here is ready for application to catchment-averaged processes, as well as modeling the role of muons in variable erosion rate scenarios.

ISSN: 0072-1077
EISSN: 2331-219X
Serial Title: Special Paper - Geological Society of America
Serial Volume: 415
Title: Eroding the land; steady-state and stochastic rates and processes through a cosmogenic lens
Title: In situ-produced cosmogenic nuclides and quantification of geological processes
Author(s): Heimsath, Arjun M.
Author(s): Siame, Lionel L.editor
Author(s): Bourles, Didier L.editor
Author(s): Brown, Erik T.editor
Affiliation: Dartmouth College, Department of Earth Sciences, Hanover, NH, United States
Affiliation: Universite Paul Cezanne, Aix-en-Provence, France
Pages: 111-129
Published: 2006
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 73
Accession Number: 2007-038897
Categories: GeomorphologyIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
S37°30'00" - S28°15'00", E141°00'00" - E153°30'00"
Secondary Affiliation: University of Minnesota, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200721
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