North Africa contains evidence of environmental change that can be used to examine past climate variability. A sedimentary sequence from the north part of Bir Tarfawi, in southern Egypt, contains a record of variable Pleistocene climate including sediments, gastropods (invertebrate fauna) and stable isotopes. The sequence dates to about 100,000 years ago and appears to document past wet (pluvial) periods in the now hyperarid area. Deposits include both clastics (sand, silt, and clay) and carbonates. Variation in sedimentation can be interpreted as evidence of climate change. Drier climate phases contain more clastics, often with higher amounts of sands. Carbonates and higher amount of muds (silts and clays) can be linked to wet climate phases. A higher resolution climate record is potentially provided by the gastropod Melanoides tuberculata, since its shell is secreted in equilibrium with the surrounding waters. Melanoides was present and collected in three of the sediment layers likely representing pluvial conditions. Oxygen stable isotope values from both sediment and Melanoides are less negative than would be expected from a prevailing westerly Atlantic precipitation. Other potential sources of water include easterly precipitation from the Indian Ocean, alternating precipitation from Atlantic and Indian Oceans, ground water and transport through streams. The stratigraphic and stable isotope record from Bir Tarfawi can be used to examine these potential sources for the variations in hydrologic conditions and can be compared to other sites in northeast Africa.
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