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Showing papers by "Jan Kramers published in 2019"


Journal ArticleDOI
TL;DR: In this article, the authors used cosmogenic 10-Beryllium (Be-10) in river sediments to estimate denudation rates and the ratio of 26-Aluminium (Al-26) to Be-10 (Al26/Be10), to constrain ages of sediment burial.
Abstract: In situ cosmogenic nuclides are an important tool for quantifying landscape evolution and dating fossil-bearing deposits in the Cradle of Humankind (CoH), South Africa. This technique mainly employs cosmogenic 10-Beryllium (Be-10) in river sediments to estimate denudation rates and the ratio of 26-Aluminium (Al-26) to Be-10 (Al-26/Be-10), to constrain ages of sediment burial. Here, we use Be-10 and Al-26 concentrations in bedrock and soil above the Rising Star Cave (the discovery site of Homo naledi) to constrain the denudation rate and the exposure history of soil on the surface. Apparent Be-10-derived denudation rates obtained from pebble- to cobble-sized clasts and coarse-sand in soil (on average 3.59 +/- 0.27 m/Ma and 3.05 +/- 0.25 m/Ma, respectively) are 2-3 times lower than the bedrock denudation rates (on average 9.46 +/- 0.68 m/Ma). In addition, soil samples yield an average Al-26/Be-10 ratio (5.12 +/- 0.27) that is significantly lower than the surface production ratio of 6.75, which suggests complex exposure histories. These results are consistent with prolonged surface residence of up to 1.5 Ma in vertically mixed soils that are up to 3 m thick. We conclude that the Be-10 concentrations accumulated in soils during the long near-surface residence times can potentially cause underestimation of single-nuclide (Be-10) catchment-wide denudation rates in the CoH. Further, burial ages of cave sediment samples that consist of an amalgamation of sand-size quartz grains could be overestimated if a pre-burial Al-26/Be-10 ratio calculated from the surface production is assumed.

15 citations


Journal ArticleDOI
TL;DR: In this article, the authors show that the relative ages of hornblende and biotite from Kirwanveggan and Sverdrupfjella gneisses are consistent with rapid uplift in a single event.

9 citations


Journal ArticleDOI
TL;DR: In this paper, a combination of palynology, sedimentology, and coal petrology is used to correlate the Springbok Flats coal zones with other southern African coal-bearing successions.
Abstract: Strata of the Springbok Flats, Ellisras and Tshipise (Soutpansberg-Pafuri) basins of South Africa are considered to have been deposited contemporaneously with those of the main Karoo Basin (MKB), but lithological differences complicate precise correlation. In this study, palynofloras from recently drilled boreholes in the Springbok Flats Basin (SFB) are used to correlate the Springbok Flats coal zones with other southern African coal-bearing successions. Permian palaeoenvironments of the SFB are reconstructed through a combination of palynology, sedimentology, and coal petrology. The lower coal zone (LCZ) palynoflora best correlates with Palynozone K4 in the MKB (equivalent to the Witbank No. 4 seam, Vryheid Formation) and can also be associated with Biozone D of the Waterberg Coalfield (Ellisras Basin), and the Vereeniging top seam in the New Vaal Colliery, northern Karoo Basin. The upper coal zone (UCZ) palynoflora of the SFB correlates closely with the Gwembe Formation (mid-Zambezi Basin, Zambia), Biozone E of the Waterberg Coalfield (Ellisras Basin), and Biozone KK 3 (Kalahari Karoo Basin, Botswana). A new radioisotopically constrained palynozonation for the MKB allows relative ages to be assigned to the coal zones of the SFB: Kungurian for the LCZ, and Roadian for the UCZ. Palynology is a useful tool in correlating these economically important strata across southern Africa.

5 citations