Characteristics and OSL minimum ages of relict fluvial deposits near Sossus Vlei, Tsauchab River, Namibia, and a regional climate record for the last 30 ka

The present end-point of the Tsauchab River is at Sossus Vlei, 30 km into the Namilb Sand Sea. Interdune deposits in three depressions west and southwest of the vlei include channel and interdune lithofacies associations but no deposits typical of river end-points or of groundwater seepage into interdune areas. The two lithofacies associations show that the Tsauchab River extended further into the sand sea in the past. It had a well-developed channel and a higher flow than today that caused flooding of adjacent interdune areas. OSL 4-mm aliquot minimum ages indicate that the Tsauchab River reached 2-3 km beyond its present end-point at ca. 25 ka and ca. 9-7 ka, and that the river was more active from 0.9-0.3 ka. The eastward migration of the river end-point since ca. 7 ka suggests a reduction in flood magnitude accompanied by the gradual invasion of the Sossus Vlei area by dunes. The regional data indicate an additional wet interval at ca. 15 ka that is so far not recorded in the Sossus area. Copyright (C) 2006 John Wiley & Sons, Ltd.