Quaternary Environmental and Climatic Changes in Egypt: Proxies from Sedimentary Records

Abstract

The Quaternary sediments in Egypt record the interplay of several factors, the most important of which are marine, fluvial, terrestrial and climatic factors. According to the strength of each factor, the Egyptian territories are subdivided into several basins reflecting the potential depositional environments. The present review promotes the Quaternary sediments of the Nile Delta, the North Western coast, the Western Desert and the Red Sea and Gulf of Aqaba coasts as proxies for Quaternary paleoclimate. The Quaternary Nile Delta sediments clearly reflect the African monsoons and the associated Nile floods correlated with the Eastern Mediterranean and global marine isotope stratigraphy. The fossil records of both planktonic and benthonic foraminifera (Pl/Be) and their δ18O represent potential references to Marine Isotope Stages (MIS) and sea level changes. Pollen and spores, δ13C, C3 and C4 plants record paleovegetation cover, and thus paleoenvironments and paleoclimate. It has been globally agreed that the primary control of climate changes and the region’s hydrological cycle are the insolation-driven changes in the strength and shifting of the Intertropical Convergence Zone (ITCZ), and therefore the intensity and northward extent of the African Humid Period (AHP), non-excluding the Atlantic westerlies (NAO). Such conditions induced intervals of heavy rainfall in Egypt as well as the Nile Headwaters. In Egyptian Sahara, such heavy rains charged the groundwater and dissolved the Paleocene–Eocene carbonate leaving deposits of lacustrine and freshwater carbonate and other karstic landforms. These terrestrial deposits supported with the calibrated age dating are used as proxies for paleoclimate along the Sahara. At the Red Sea coast, the growth of coral reefs and deposition of thick fluvial gravels are used as proxies for climate and sea level changes, while the aeolianites and paleosols are the available proxies at the NW Mediterranean coast of Egypt. On the other hand, the increase in outflow of the River Nile led to stagnation of freshwater over the marine water and formation of sapropel layers in Eastern Mediterranean. The oxygen isotopes and age determination of the above-mentioned materials allow correlation with global climate conditions; however, such correlation is not always isochronic. The offsets are explained by the presence of regional driving forces overriding the global influences.