Terrigenous-Carbonate Sediment Interface (Late Quaternary) Along the Northwestern Margin of the Nile Delta, Egypt

Abstract

This petrological study characterizes the nature of various mixtures of terrigenous and carbonate sedimentary sequences of Late Pleistocene to Holocene age along the northwestern margin of the Nile delta in the Alexandria region, Egypt. Focus on the composition and proportions of sand-sized components serves to distinguish siliciclastic sediments of the River Nile to the east from carbonate sediments of the Arab's Gulf carbonate province to the west. Considered in this investigation are the petrologic attributes of (1) surface facies in shallow marine environments and prominent carbonate ridges, and also of (2) subsurface sediments recovered in radiocarbon-dated borings collected south and west of Abu Qir to Borg el Arab. Surface and subsurface sections can be correlated on the basis of compositional analysis. Distribution in time and space of the mixed terrigenous-carbonate facies is delineated in the Alexandria Lake Maryut region. Temporal and geographic shifts of this facies along the coast are induced by natural (eustatic sea level, subsidence, transport processes) and also man-induced factors. The latter include irrigation projects along the western delta margin, and development of coastal structures, particularly in the Agami to Abu Qir region. It is proposed that the terrigenous-carbonate sediment interface can be used as a gauge to detect changes in coastal depositional patterns along the northwest delta. Displacement of this interface would be induced by changes such as coastline configuration, erosion rates, and amount and nature of the sediment input from River Nile branches flowing to the Mediterranean.