Late Quaternary Evolution of the Northwest Nile Delta and Adjacent Coast in the Alexandria Region, Egypt

Abstract

The late Pleistocene to Recent evolution of the Alexandria region, Egypt, is interpreted by sedimentologic-stratigraphic study of radiocarbon-dated borings. Petrological and faunal analyses define major lithofacies, and mapping of these subsurface sequences depicts spatial and temporal distributions of sedimentary environments. Lithofacies distributions are used to compile time-slice paleogeographic maps for the past 35,000 years. New information is provided on the origin and history (since ~6,000 years BP) of Maryut lake, the major coastal water body south and west of Alexandria. Lithostratigraphic criteria are developed to define the western limit of the Nile delta, which lies within the study area. Mapping of subsurface facies reveals that the western limit of Maryut lake (former Lake Mareotis) demarcates the western boundary of the delta; this boundary has not significantly shifted since late Pleistocene time. Facies distributions are related to natural factors which control sedimentation and coastal development in this area, and include eustatic sea-level and climatic oscillations, subsidence (compaction, isostatic depression), neotectonic uplift and sediment transport processes.

Integration of core study with geomorphic analysis serves to differentiate the impact of natural from human-induced factors. Our investigation highlights the extent to which the Alexandria region has been influenced by man, and reveals that anthropogenic factors have become a dominant control on depositional systems and coastal plain evolution. Combined effects of natural (primarily sea-level rise and neotectonism) and human-induced phenomena (e.g., wetland loss and severe pollution) are inducing changes which threaten this low-lying area. Geologic and geomorphic analyses provide information that is essential to effective coastal management of the Alexandria region.