Browsing by Author "Kempf, Jurgen"
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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 Fossil evidence for perennial lake conditions during the Holocene at Etosha Pan, Namibia(2006) Hipondoka, Martin; Jousse, H.; Kempf, Jurgen; Busche, DetlefETOSHA PAN, A LARGE (4760km2), ENDORheic depression situated in north-central Namibia, has been claimed to be essentially a wind-deflated landform. The pan was assumed by some researchers to have developed under persistent semi-arid conditions,which were alleged to have prevailed in the region for at least the last 140 000 years. Recent field evidence points to the contrary. This evidence includes a significant number of fossils belonging to, amongst others, semi-aquatic antelopes such as sitatunga, which are diagnostically indicative of perennial lake conditions in the area. These species have previously never been reported from Etosha National Park, either as fossils or extant. Here we indicate the significance of these findings and their implications for the palaeo-environment of the Etosha region.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.Item Source of lunette dune sediments: A geomorphic terrain analysis approach in Etosha National Park, Namibia(2004) Hipondoka, Martin; Busche, Detlef; Kempf, JurgenThe presence of so-called lunette dunes in the lee of pans in northern Namibia sprouted a discussion on the formation of the shallow basins related to them. These lunette dunes are made up of larger particles than those found in the pans, from which the sediments are thought to have originated. At Etosha Pan, this contradiction is compounded by the fact that the dunes are found on the northwestern and western side of the pan, whilst the prevailing dominant wind, believed to have played a formative role in their development, blows from the northeast. Ancillary data, in concert with high-resolution, multi-date satellite imagery were examined through the prism of geomorphic terrain analysis. The resultant indicators unequivocally point to the Ekuma delta, on the northwestern rim of the pan, in direct opposition to the pan floor proper, as the source of these dune sediments. It is therefore probable that coarser sediments found on the lee side of similar pans can be similarly explained as originating from former inlet deposition and not from wind excavation in the process of pan initiation as popularly held.