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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/esurf-2017-76
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
16 Jan 2018
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Earth Surface Dynamics (ESurf) and is expected to appear here in due course.
Tracking the 26Al/10Be source-area signal in sediment-routing systems of arid central Australia
Martin Struck1, John D. Jansen2, Toshiyuki Fujioka3, Alexandru T. Codilean1, David Fink3, Réka-Hajnalka Fülöp1,3, Klaus M. Wilcken3, David M. Price1, Steven Kotevski3, L. Keith Fifield4, and John Chappell4 1School of Earth and Environmental Sciences, University of Wollongong, Wollongong 2522, Australia
2Department of Geoscience, Aarhus University, 8000 Aarhus C, Denmark
3Australian Nuclear Science and Technology Organisation, Lucas Heights 2234, Australia
4Research School of Earth Sciences, Australian National University, Canberra 0200, Australia
Abstract. Sediment-routing systems continuously transfer information and mass from eroding source areas to depositional sinks. Understanding how these systems alter environmental signals is critical when it comes to inferring source-area properties from the sedimentary record. We measure cosmogenic 10Be and 26Al along three large sediment-routing systems (~ 100,000 km2) in central Australia with the aim of tracking downstream variations in 26Al/10Be inventories and to identify the factors responsible. By comparing 56 new cosmogenic 10Be and 26Al measurements in stream sediments with matching data (n = 55) from source areas, we show that 26Al/10Be inventories in hillslope bedrock and soils set the benchmark for relative downstream modifications. Lithology is the primary determinant of erosion-rate variations in source areas and despite sediment mixing over hundreds of kilometres downstream a distinct lithological signal is retained. Postorogenic ranges yield catchment erosion rates of ~ 6–11 m/m.y. and silcrete-dominant areas erode as slow as ~ 0.2 m/m.y. 26Al/10Be inventories in stream-sediments reveal overall downstream-increasing minimum cumulative burial terms up to ~ 1.1 m.y. but more generally ~ 400–800 k.y. The magnitude of the burial signal correlates with increasing sediment cover downstream and reflects assimilation from storages with long exposure histories, such as alluvial fans, desert pavements, alluvial plains, and aeolian dunes. We propose that the tendency for large alluvial rivers to mask their 26Al/10Be source-area signal differs according to geomorphic setting. Signal preservation is favoured by i) high sediment supply rates, ii) high mean runoff, and iii) a thick sedimentary basin pile. Conversely, signal masking prevails in landscapes of i) low sediment supply, ii) discontinuous sediment flux, and iii) juxtaposition of sediment storages with notably different exposure histories.
Citation: Struck, M., Jansen, J. D., Fujioka, T., Codilean, A. T., Fink, D., Fülöp, R.-H., Wilcken, K. M., Price, D. M., Kotevski, S., Fifield, L. K., and Chappell, J.: Tracking the 26Al/10Be source-area signal in sediment-routing systems of arid central Australia, Earth Surf. Dynam. Discuss., https://doi.org/10.5194/esurf-2017-76, in review, 2018.
Martin Struck et al.
Martin Struck et al.

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Short summary
Measurements of cosmogenic nuclides 10Be and 26Al in sediment along central Australian streams show that lithologically-controlled magnitudes of source-area erosion rates (0.2–11 m/m.y.) are preserved downstream despite sediment mixing. Conversely, downstream-increasing sediment burial signals (> 400 k.y.) indicate sediment incorporation from adjacent, long-exposed storages, which, combined with low sediment supply and discontinuous flux, likely favours source-area 10Be-26Al signal masking.
Measurements of cosmogenic nuclides 10Be and 26Al in sediment along central Australian streams...
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