Using 10Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africa

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dc.contributor.authorDirks, PJHMen_AU
dc.contributor.authorPlaczek, CJen_AU
dc.contributor.authorFink, Den_AU
dc.contributor.authorDosseto, Aen_AU
dc.contributor.authorRoberts, Een_AU
dc.date.accessioned2021-12-16T03:58:35Zen_AU
dc.date.available2021-12-16T03:58:35Zen_AU
dc.date.issued2016-07en_AU
dc.date.statistics2021-11-14en_AU
dc.description.abstractConcentrations of cosmogenic 10Be, measured in quartz from chert and river sediment around the Cradle of Humankind (CoH), are used to determine basin-averaged erosion rates and estimate incision rates for local river valleys. This study focusses on the catchment area that hosts Malapa cave with Australopithecus sediba, in order to compare regional versus localized erosion rates, and better constrain the timing of cave formation and fossil entrapment. Basin-averaged erosion rates for six sub-catchments draining the CoH show a narrow range (3.00 ± 0.28 to 4.15 ± 0.37 m/Mega-annum [Ma]; ±1σ) regardless of catchment size or underlying geology; e.g. the sub-catchment with Malapa Cave (3 km2) underlain by dolomite erodes at the same rate (3.30 ± 0.30 m/Ma) as the upper Skeerpoort River catchment (87 km2) underlain by shale, chert and conglomerate (3.23 ± 0.30 m/Ma). Likewise, the Skeerpoort River catchment (147 km2) draining the northern CoH erodes at a rate (3.00 ± 0.28 m/Ma) similar to the Bloubank-Crocodile River catchment (627 km2) that drains the southern CoH (at 3.62 ± 0.33 to 4.15 ± 0.37 m/Ma). Dolomite- and siliciclastic-dominated catchments erode at similar rates, consistent with physical weathering as the rate controlling process, and a relatively dry climate in more recent times. Erosion resistant chert dykes along the Grootvleispruit River below Malapa yield an incision rate of ∼8 m/Ma at steady-state erosion rates for chert of 0.86 ± 0.54 m/Ma. Results provide better palaeo-depth estimates for Malapa Cave of 7–16 m at the time of deposition of A. sediba. Low basin-averaged erosion rates and concave river profiles indicate that the landscape across the CoH is old, and eroding slowly; i.e. the physical character of the landscape changed little in the last 3–4 Ma, and dolomite was exposed on surface probably well into the Miocene. The apparent absence of early Pliocene- or Miocene-aged cave deposits and fossils in the CoH suggests that caves only started forming from 4 Ma onwards. Therefore, whilst the landscape in the CoH is old, cavities are a relatively young phenomenon, thus controlling the maximum age of fossils that can potentially be preserved in caves in the CoH. © 2016 Elsevier Ltd.en_AU
dc.identifier.citationDirks, P. J. H. M., Placzek, C. J., Fink, D., Dosseto, A., & Roberts, E. (2016). Using 10Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africa. Journal of Human Evolution, 96, 19-34. doi:10.1016/j.jhevol.2016.03.002en_AU
dc.identifier.issn0047-2484en_AU
dc.identifier.journaltitleJournal of Human Evolutionen_AU
dc.identifier.pagination19-34en_AU
dc.identifier.urihttps://doi.org/10.1016/j.jhevol.2016.03.002en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/12491en_AU
dc.identifier.volume96en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectSedimenten_AU
dc.subjectErosionen_AU
dc.subjectCavesen_AU
dc.subjectBeryllium 10en_AU
dc.subjectWatershedsen_AU
dc.subjectFossilen_AU
dc.titleUsing 10Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africaen_AU
dc.typeJournal Articleen_AU
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