Erosion and the sediment conveyor in central Australia

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dc.contributor.authorJansen, JDen_AU
dc.contributor.authorChappell, Jen_AU
dc.contributor.authorStruck, Men_AU
dc.contributor.authorEccleshall, SVen_AU
dc.contributor.authorFujioka, Ten_AU
dc.contributor.authorCodilean, ATen_AU
dc.contributor.authorFülöp, RHen_AU
dc.contributor.authorFink, Den_AU
dc.contributor.authorCohen, TJen_AU
dc.contributor.authorNanson, GCen_AU
dc.date.accessioned2020-06-12T00:55:31Zen_AU
dc.date.available2020-06-12T00:55:31Zen_AU
dc.date.issued2016-02-29en_AU
dc.date.statistics2020-06-01en_AU
dc.description.abstractWhy are the Neogene sedimentary fills across central Australia generally thin and discontinuous? One long-standing explanation is that sluggish tectonism and intensified aridity have combined to suppress rates of erosion and sediment production yielding a landscape crowded with inherited, preMiocene forms. Quantifying rates of sediment production, residence time and transport is possible with numerous methods, but the recent growth of cosmogenic nuclide (CN) analysis has provided unprecedented quantitative insights to rates of landscape evolution. Measurements of in situ produced cosmogenic 10Be and 26Al integrate rates of surface processes over million-year timescales—the last part of the Neogene in which aridity has strengthened across the continental interior. We present a compilation of ~600 published and unpublished 10Be and 26Al measurements from central Australia with a focus on the Neogene Eyre Basin and its periphery. Outlying and inlying bedrock uplands serve as engines of sediment production via erosion of bedrock. Surrounding the bedrock outcrops are vast sediment conveyors of varying efficiency and tempo: hillslopes, pediments, and alluvial fans are interim storage/burial zones for sediment in transit to the network of low-gradient rivers, dunes, and playas towards base level. Interactions between fluvial and aeolian processes are especially pertinent to sediment flux in the Eyre Basin. Major rivers such as the Cooper and Finke traverse dunefields in their lower reaches where quantities of alluvia are recirculated into dunes and vice versa. Tracking the trajectories of sediment from source-to-sink (including aeolian recirculation) remains a major challenge, but is central to unravelling the sedimentary dynamics of central Australia's Neogene basins. Based on the CN compilation we estimate 1) spatially averaged erosion rates at the scale of a hillslope or river catchment; 2) pointbased erosion rates on bedrock surfaces; 3) residence time of sediment in hillslope regolith and alluvial fans; and 4) cumulative burial history of sediments in transit. Catchment-scale erosion rates (n~100) are consistently low (<10 m/Myr) and include some of the lowest rates ever measured (~0.3 m/Myr); however, a small group of catchments in the Flinders Ras yield higher erosion rates (~30–60 m/Myr). Bedrock hillslopes (n~200) tend to erode even slower (<5 m/Myr), with a subset of Flinders Ras sites again being the exception (~10–30 m/Myr) and suggesting the influence of recent tectonism. Several CN depth-profiles measured on hillslopes and alluvial fans indicate sediment residence times >0.5 Myr, and high-resolution sampling along three hillslopes with differing morphology (linear, convex, and concave) reveals major variations in sediment production and transport rates that hint at the long-term evolution. In the rivers, fluvial sediments show a weak tendency to increase cumulative burial history downstream (1–2 Myr), consistent with the expanding accommodation space for storage and burial. Dune sediments sampled in the Simpson and Tirari dunefields (n~16) contain cumulative burial histories (up to 1.5 Myr) similar to that of the intersecting rivers. This points to an intimate mix of fluvial and aeolian processes in areas approaching base level. Curiously, these sediments occur in the lowest part of the continent and contain the longest histories of cumulative burial, yet do not form part of the thickest sedimentary fills in the Eyre Basin.en_AU
dc.identifier.citationJansen, J. D., Chappell, J., Struck, M., Eccleshall, S. V., Fujioka, T., Codilean, A. T., Fülöp, R. H., Fink, D., Cohen, T. J., & Nanson. G. C. (2016). Erosion and the sediment conveyor in central Australia. Paper presented at the Neotectonics on the Australian Plate: New Science for Energy, Mineral and Groundwater Systems, and Hazard Assessment Seminar, 26th February to 1st March 2016, Canberra, Australia.en_AU
dc.identifier.conferenceenddate1 March 2016en_AU
dc.identifier.conferencenameNeotectonics on the Australian Plate: New Science for Energy, Mineral and Groundwater Systems, and Hazard Assessment Seminaren_AU
dc.identifier.conferenceplaceCanberra, Australiaen_AU
dc.identifier.conferencestartdate26 February 2016en_AU
dc.identifier.govdoc9621en_AU
dc.identifier.urihttps://www.gsa.org.au/Public/Specialist/Environmental_Engineering___Hydrogeology_EEHSG/Public/Specialist_Groups/Environmental_Engineering___Hydrogeology_EEHSG.aspx?hkey=ab786cde-2814-423d-8585-1fc08b14bf14en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/9603en_AU
dc.language.isoenen_AU
dc.publisherGeological Society of Australiaen_AU
dc.subjectSedimentsen_AU
dc.subjectErosionen_AU
dc.subjectEvolutionen_AU
dc.subjectAustraliaen_AU
dc.subjectSedimentary basinsen_AU
dc.subjectRiversen_AU
dc.subjectTertiary perioden_AU
dc.subjectPlate tectonicsen_AU
dc.subjectEnvironmental transporten_AU
dc.subjectBeryllium 10en_AU
dc.subjectAluminium 26en_AU
dc.subjectAlluvial depositsen_AU
dc.titleErosion and the sediment conveyor in central Australiaen_AU
dc.typeConference Abstracten_AU
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