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Soil production and transport on postorogenic desert hillslopes quantified with (super 10) Be and (super 26) Al

Martin Struck, John D. Jansen, Toshiyuki Fujioka, Alexandru T. Codilean, David Fink, David L. Egholm, Reka-Hajnalka Fulop, Klaus M. Wilcken and Steven Kotevski
Soil production and transport on postorogenic desert hillslopes quantified with (super 10) Be and (super 26) Al
Geological Society of America Bulletin (January 2018) 130 (5-6): 1017-1040

Abstract

Hillslopes stand at the top of the geomorphic conveyor belt that produces and transports mass throughout landscapes. Quantification of the tempo of hillslope evolution is key to identifying primary sediment production and understanding how surface processes shape topography. We measured cosmogenic (super 10) Be and (super 26) Al on three desert hillslopes in postorogenic central Australia and quantified their soil dynamics and evolution. We found that hillslope morphology is governed by lithological factors, and differing nuclide abundances reflect the main sediment transport processes. Slope wash is widespread, and shrink-swell soil processes drive downslope creep and upward migration of gravels detached from underlying bedrock. We applied Monte Carlo-based inversion modeling to reconstruct soil production and the exhumation histories of stony mantle gravels. Underlying silty soils derive from eolian dust inputs dating to at least 0.2 Ma and possibly more than 1 Ma, in line with intensified aridity. Exposed bedrock erodes at approximately 0.2-7 m/m.y., and under soil, it erodes at maximum rates of <0.1 m/m.y. up to 10 m/m.y. Accordingly, particles spend 2-6 m.y. or more in the upper 0.6 m of the bedrock column and an additional approximately 0.2-2 m.y. or more within hillslope soils. Such long periods near the surface result in surface particles acquiring inherently low (super 26) Al/ (super 10) Be ratios. Bedrock erodibility underpins regional variations in erosion rate, and the slow tempo of hillslope evolution is largely independent of base level. This suggests a distinctive top-down evolution among postorogenic hillslopes set by authigenic rates of sediment production, rather than by fluvial incision as in tectonically active settings.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 130
Serial Issue: 5-6
Title: Soil production and transport on postorogenic desert hillslopes quantified with (super 10) Be and (super 26) Al
Affiliation: University of Wollongong, School of Earth and Environmental Sciences, Wollongong, N.S.W., Australia
Pages: 1017-1040
Published: 20180102
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 127
Accession Number: 2018-032328
Categories: SoilsGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017400
Illustration Description: illus. incl. sects., 4 tables, sketch maps
S33°00'00" - S19°00'00", E131°00'00" - E147°00'00"
Secondary Affiliation: Aarhus University, DNK, DenmarkAustralian Nuclear Science and Technology Organisation, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, 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: 201817
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