Submergence and burial of ancient coastal sites on the subsiding Nile delta margin, Egypt

Abstract

Ancient sites originally positioned along the Nile delta’s coastal margin are used as gauges to measure effects of «eustatic» sea-level rise (~1 mm/year) and land lowering (= subsidence) of the sediment substrate beneath settlements during the late Holocene. The combined effect of these two factors, referred to as relative sea-level change, resulted in submergence and/or burial of the base of most sites along the delta at variable rates exceeding 1 mm/year. Based on these factors, submergence of sites to depths of 5-7 m is recorded in Abu Qir Bay off the NW delta; higher values (lowering to 5 mm/year) are recorded along the NE corner of the delta. Variations of substrate topography laterally along the delta margin are caused by differences of seismicity, isostatic depression, and sediment compaction and remobilization that affect underlying deposits. Geologically recent lowering of the northern Nile delta plain surface is comparable to that of many world delta margins.