Precipitation Source Inferred from Stable Isotopic Composition of Pleistocene Groundwater and Carbonate Deposits in the Western Desert of Egypt

Mohamed Sultan and Neil Sturchio
Environmental Research Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439

Fekri A. Hassan
Institute of Archaeology, University College London, 31-34 Gordon Square, London WCIH OPY. United Kingdom

Mohamed Abdel Rahman Hamdan
Department of Geology, Faculty of Science, Cairo University, Cairo, Egypt

Abdel Moneim Mahmood
Ain Shams University, Cairo, Egypt

Zeinhom El Alfy
Egyptian Geological Survey and Mining Authority, 3 Salah Salem S t., Abbassia, Cairo, Egypt


Tom Stein
Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130

Received February 14, 1996
< back

An Atlantic source of precipitation can be inferred from stable isotopic data (H and 0) for fossil groundwaters and uranium-series-dated carbonate spring deposits from oases in the Western Desert of Egypt. In the context of available stable isotopic data for fossil groundwaters throughout North Africa, the observed isotopic depletions (dD -72 to -81%0; d18O -10.6 to -11.5%0) of fossil (>32,000 yr B.P.) groundwaters from the Nubian aquifer are best explained by progressive condensation of water vapour from paleowesterly wet oceanic air masses that traveled across North Africa and operated at least as far back as 450,000 yr before the present. The values of d18O (17.1 to 25.9%0) for 45,000- to >450,000-yr-old tufas and vein-filling calcite deposits from the Kharga and Farafra Oases are consistent with deposition from groundwaters having oxygen isotopic compositions similar to those of fossil groundwaters sampled recently at these locations.