Stratigraphy and sedimentation of a Neogene—Quaternary section in the Nile Delta area (A.R.E.)

Abstract

Information available for the reconstruction of Neogene and Quaternary stratigraphy and sedimentology according to the succession recorded in the subsurface of the Nile Delta, has been obtained through oil exploration. The reconstruction presented here is based on information gathered from approximately twenty oil wells and on the relative seismic sections. The section is relatively uniform over the whole delta and is constituted by three sedimentary cycles. The most ancient, which comprises at least the Middle and Upper Miocene, is incompletely sampled since the wells do not reach the bottom of that series. The section begins at the bottom with the pelitic sedimentation of a fairly deep sea or outer shelf (Sidi Salim Fm.) and ends abruptly in the Messinian with the deposition of a fluvial-deltaic series (Qawasim Fm.) and evaporites (Anhydrites of Rosetta Fm.). A fairly pronounced emersion follows, accompanied by phenomena of gravity tectonics, slumpings and subaerial erosion. A sandy basal formation of Early Pliocene age (Abu Madi Fm.) lies on this erosional surface. A clayey formation of open-sea type follows (Kafr El Sheikh Fm.). The Pliocene—Quaternary cycle ends with coastal and fluvial-deltaic sediments (El Wastani and Mit Ghamr Fms.). The Holocene cycle is represented by a few tens of meters of coastal and lagoonal sediments. The end of the Miocene sedimentation is comparable with that which occurred in all the rest of the Mediterranean Basin during the Messinian and it bears a close relationship to the “salinity crisis”. In this particular case, the deposition of nearly one thousand meters of Messinian sediments of the Qawasim Formation, with fluvial-deltaic characteristics, in a basin which, up until a very short time before, had been fairly deep, seems to indicate — in the absence of evidence of regional tectonism — a sudden lowering of the average level of the Mediterranean Sea. The Lower Pliocene shows a fairly rapid restabilization of the bathymetric and environmental conditions which had governed the sedimentation during the Miocene, before the deposition of the Qawasim Formation. Paper presented by IEOC at the Egyptian General Petroleum Corporation 5th Exploration Seminar, Cairo, A.R.E. November 1976.