Geochronology and climate change of the Pleistocene-Holocene transition inthe Darb el Arba'in Desert, Eastern Sahara

More than 25 years of geoarchaeological investigations in the hyperarid reg ions of southwestern Egypt and northwestern Sudan, the Darb el Arba'in dese rt, demonstrate that Holocene pluvial conditions began about 9800 yr B.P., essentially at the end of Younger Dryas cooling. The eastern Sahara changed from a hyperarid, lifeless desert dominated by eolian activity and deflati on to an and to semiarid savanna that attracted Sudano-Sahelian fauna and N eolithic pastoralists to the region until about 5000 yr B.P., when the curr ent episode of hyperaridity ensued. In the lake and playa basins of the eas tern Sahara, Younger Dryas time, about 10,800-9700 yr B.P., is represented by an erosional hiatus, during which deflation of basins occurred. The only deposition that may have occurred during this hyperarid period is sand she et aggradation and dune formation consistent with the Sahara being hyperari d during the glacial periods. Younger Dryas-age eolian deposits have yet to be identified by optically stimulated luminescence (OSL). The current hype raridity would imply that glacial conditions exist in the northern hemisphe re, yet the opposite is the case. Perhaps global glaciation lags the onset of Saharan hyperaridity by several millennia, and the area is in a transiti onal phase much like the Bolling and Allerod periods. (C) 2001 John Wiley & Sons, Inc.