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 investigatio ns, the now hyperarid northwestern Sudan and southwestern Egypt experi enced a period of greater effective moisture during early and middle H olocene 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 paleolake-forming 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, an d 1; the 90-65 ka episode may be correlated with substage 5c or 5a. Ou r results support the contention that past pluvial episodes in North A frica corresponded to the interglacial periods farther north. Ages of lacustrine carbonates from existing eases and from the sand sheet fail to indicate pluvial conditions between about 60 and 30 ka. Age result s and held relationships suggest that the;oldest lake- and ground-wate r-deposited carbonates were much more extensive than those of the youn ger period, and that carbonate of the latest wet periods were geograph ically localized within depressions and buried channels.