Aeolianite sedimentation along the northwestern coast of Egypt: Evidence for middle to late quaternary aridity

Abstract

Aeolian sediments along the northwestern coast of Egypt are described, analyzed for oxygen and carbon isotopes and dated using radiocarbon, U-Series and amino-acid geochronology. Although deposition of the aeolianites along the northwestern Mediterranean coast of Egypt does not necessarily indicate regressive sea-level events, their development is often associated with arid climatic conditions. The study of the aeolian sediments which constitute part of the coastal calcarenite ridges that are distributed parallel to the presen shoreline, reveals the presence of at least four arid climatic phases following four major humid phases associated with high marine levels. The aeolian phases are characterized by high positive δ 18O and δ 13C values and are related to aminozones A (Holocene), C (Oxygen Isotope Substage 5a/5c), E (Oxygen Isotope Substage 5e) and G (Oxygen Isotope Stage 9), which are represented by the Coastal ridge, El-Max-Abu Sir ridge and the complex cycles of Gebel Maryut ridge respectively. A positive increasing trend of both δ 18O and δ 13C values is observed from Gebel Maryut ridge to the Coastal ridge. This indicates a general increasing of aridity with short intermittent moist conditions during which the reddish brown palaeosols were developed with their characteristic low δ 18O and δ 13C values.