Ephemeral rivers today terminate in playas adjacent to the eastern part of the Namib Sand Sea, although there is evidence that these fluvial systems penetrated further west in the past. There are water-lain sediments exposed in interdune areas of the northern Namib Sand Sea associated with the former course of the Tsondab River, which are central to palaeoenvironmental reconstruction in the region. These deposits indicate that there was increased moisture availability in this presently hyper-arid region and/or the catchments of the rivers to the east of the Sand Sea in the Great Escarpment. Until now the chronology for the deposition of these sediments has been based on radiocarbon (14C) dates on carbonate materials. The validity of these ages is problematic and 14C limits the timescale to which these sediments can be dated. Keywords: Northern Namib Sand Sea, Interdune deposits, OSL dating, Palaeohydrology, Palaeoenvironments.