Ages of Quaternary pluvial episodes determined by uranium-series and radiocarbon dating of lacustrine deposits of Eastern Sahara

As documented by radiocarbon dating and geoarchaeological investigations, the now hyperarid northwestern Sudan and southwestern Egypt experienced a period of greater effective moisture during early and middle Holocene time, about 10-5 ka. We have used the uranium-series technique to date lacustrine carbonates from Bir Tarfawi, Bir Sahara East, Wadi Hussein, Oyo Depression, and the Great Selima Sand Sheet localities. Results indicate five paleolakeforming episodes occurred at about 320-250, 240-190, 155-120, 90-65 and 10-5 ka. Four of these five pluvial episodes may be correlated with major interglacial stages 9, 7, 5e, and 1; the 90-65 ka episode may be correlated with substage 5c or 5a. Our results support the contention that past pluvial episodes in North Africa corresponded to the interglacial periods farther north. Ages of lacustrine carbonates from existing oases and from the sand sheet fail to indicate pluvial conditions between about 60 and 30 ka. Age results and field relationships suggest that the oldest lake- and ground-water-deposited carbonates were much more extensive than those of the younger period, and that carbonate of the latest wet periods were geographically localized within depressions and buried channels.