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Tracking the 10Be-26 Al source-area signal in sediment-routing systems of arid central Australia.
- Source :
- Earth Surface Dynamics; 2018, Vol. 6 Issue 2, p329-349, 21p
- Publication Year :
- 2018
-
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 <superscript>10</superscript>Be and <superscript>26</superscript>Al along three large sediment-routing systems (~100 000 km<superscript>2</superscript>) in central Australia with the aim of tracking downstream variations in <superscript>10</superscript>Be-<superscript>26</superscript>Al inventories and identifying the factors responsible for these variations. By comparing 56 new cosmogenic <superscript>10</superscript>Be and <superscript>26</superscript>Al measurements in stream sediments with matching data (n D55) from source areas, we show that <superscript>10</superscript>Be-<superscript>26</superscript>Al 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 ~6-11 mMyr<superscript>-1</superscript> and silcrete-dominant areas erode as slow as ~0.2 mMyr<superscript>-1</superscript>. <superscript>10</superscript>Be-<superscript>26</superscript>Al inventories in stream sediments indicate that cumulative-burial terms increase downstream to mostly ~400-800 kyr and up to ~1.1 Myr. 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 <superscript>10</superscript>Be-<superscript>26</superscript>Al 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. [ABSTRACT FROM AUTHOR]
- Subjects :
- SOIL erosion
RESERVOIRS
Subjects
Details
- Language :
- English
- ISSN :
- 21966311
- Volume :
- 6
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Earth Surface Dynamics
- Publication Type :
- Academic Journal
- Accession number :
- 130808959
- Full Text :
- https://doi.org/10.5194/esurf-6-329-2018