Browsing by Author "Mauz, B."
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Item Chronology of sand ridges and the Late Quaternary evolution of the Etosha Pan, Namibia(2014) Hipondoka, Martin; Mauz, B.; Kempf, Jurgen; Packman, S.; Chiverrell, R.C.; Bloemendal, J.Etosha Pan, situated at the southern border of tropical Africa, is a vast endorheic plain in Namibia's semi-arid north. The most recent studies agree that the pan was the floor of a former lake with varying water levels. Here we explored this idea further by investigating the link between lake-level change and records of late Pleistocene and Holocene climate change. The varying lake levels were inferred through sediment analysis and optical dating of sand deposits that form ridges parallel to the current shore along the northern and western margins of the pan. Our results support the view that the sand ridges are shoreline deposits of an evaporitic lake. The ridges result from the interplay between intermittent river discharge and riverine sediment supply from the north, prevailing north-easterly wind and shore-parallel waves. Therefore they are a proxy for former levels of a perennial lake. We infer higher levels during the late Pleistocene and a drastic drop shortly after 10 ka. Since around 8 ka Etosha Pan was covered by a shallow water body. This lake water-level reconstruction is not in line with the histories of ITCZ migration and strength of Benguela current upwelling. We confirm that the linkages between the evolution of the Etosha Pan and the climate mechanisms driving hydrological changes in subtropical southwest Africa are poorly resolved and need further investigation.Item Reconnaissance survey of radioisotopes in soil and possible impact on seasonal Anthrax outbreak at Etosha National Park, Namibia(University of Namibia, 2013) Hipondoka, Martin; Mauz, B.; Nande, E.M.; Bezuidenhout, J.Recent discovery of elevated concentrations of uranium and thorium in sediments of the Etosha Pan prompted this reconnaissance study to survey radionuclides for their possible impact on seasonal anthrax outbreaks in habitats adjacent to the pan. Plausible explanation about how animals contract anthrax is yet to be established. Because anthrax spores are non-invasive, one of the preconditions suggested for the initiation of infection is a lesion, which serves as entry point into tissue of the organism. Five samples taken from sediments at waterholes/depressions situated downwind of the pan, where the highest density of anthrax-related deaths occurs, were analysed in the laboratory using a gamma spectrometry. All sites sampled contain concentration of radionuclides higher than the crustal average, and the highest activity concentration of 93 Bq/kg 214Bi and 214Pb, for example, was recorded closest to the Etosha Pan. This suggests that the pan is the source of uranium, and thus possible that radionuclides are redistributed from the pan by prevailing wind, mobilized seasonally by running water and collected in pools in which animals drink. Alpha-emitting radionuclides can damage the renal, gastrointestinal and/or respiratory systems of exposed animals. Incurred damage is hypothesized as a likely mechanism under which spores are aided to enter the host for infection.Item Sand-ridge dynamics and the evolution of the Etosha Pan, Namibia(2012) Hipondoka, Martin; Mauz, B.; Packman, S.; Bloemendal, J.; Kempf, Jurgen; Chiverrell, R.C.