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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union
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Volume 6, issue 2 | Copyright
Earth Surf. Dynam., 6, 329-349, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 07 May 2018

Research article | 07 May 2018

Tracking the 10Be–26Al 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 Martin Struck et al.
  • 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 ( ∼ 100000km2) in central Australia with the aim of tracking downstream variations in 10Be–26Al inventories and identifying the factors responsible for these variations. By comparing 56 new cosmogenic 10Be and 26Al measurements in stream sediments with matching data (n = 55) from source areas, we show that 10Be–26Al 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. Post-orogenic ranges yield catchment erosion rates of  ∼ 6–11mMyr−1 and silcrete-dominant areas erode as slow as  ∼ 0.2mMyr−1. 10Be–26Al inventories in stream sediments indicate that cumulative-burial terms increase downstream to mostly  ∼ 400–800kyr and up to  ∼ 1.1Myr. 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 10Be–26Al 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 and (ii) juxtaposition of sediment storages with notably different exposure histories.

Publications Copernicus
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 Myr-1) are preserved downstream despite sediment mixing. Conversely, downstream-increasing sediment burial signals (> 400 kyr) 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...