Rapid Subsidence in the Nile Delta and the Effects of a Mobile Depositional Surface on Stratigraphic Facies Development: ABSTRACT

Abstract

Radiocarbon-data late Quaternary sedimentary sections serve as a base to quantify high rates of subsidence in the northern Nile delta of Egypt. Measurements of recent vertical shifts of land relative to the sea, coupled with eustatic changes, are used to interpret temporal and spatial facies distribution patterns and delta lobe migration in the major recent depocenter in the eastern Mediterranean. The study is based largely on cores, collected during two drilling expeditions, which recovered material deposited during the past 30,000 years. These borings, plus an additional 50 core logs, allow good correlation for the region around Lake Manzala. There, variable thicknesses of Holocene marine and fluvio-marine units lie above transgressive coastal sands (upper Pleistocene to lower Holocene) and older alluvial delta-plain deposits. Mapping of these facies shows that the top of the transgressive sand becomes younger (to /approximately/ 7000 years ago) and shallower toward the south of the present coastline. Progradation of delta lobes began about 8000 years ago, and the coastline has advanced northward at a rate of approximately 1 km/100 years.