Environmental changes at the eastern Namib Desert margin before and after the Last Glacial Maximum:: New evidence from fluvial deposits in the upper Hoanib River catchment, northwestern Namibia

In the upper Hoanib River catchment area, northwestern Namibia, fine-grained silty deposits are widespread. Accumulated as river-end deposits they form excellent geomorphological archives of a highly sensitive desert-margin area. Different sedimentary complexes are separated sedimentologically and by luminescence dating. The deposits give evidence of climate oscillations at the eastern margin of the Namib Desert during the past 50,000 years. In northwestern Namibia, the dry conditions of the desert-margin area with less than 200-300 mm mean annual precipitation prevailed at similar to 60-40 ka and at similar to 34-24 ka when sediment complex-I accumulated. During the Last Glacial Maximum (LGM), fluvial activity and sedimentation were most likely interrupted due to and conditions. Between similar to 12 ka and the Mid-Holocene higher rainfall and runoff led to the aggradation of sediment complex-II. The climate was more humid than before the LGM, but drier than at present. After similar to 3 ka runoff increased and the Hoanib River re-eroded the older deposits forming deep channels. A prominent, more sandy and gravely 4 m-terrace in the upper and middle course of the Hoanib River dates to the Little Ice Age (LIA). It is likely that this terrace is genetically linked with the Amspoort Silt formation in the Lower Hoanib valley. (c) 2005 Elsevier B.V All rights reserved.