PLANKTONIC-FORAMINIFERA AND CHRONOSTRATIGRAPHY OF THE OLIGOMIOCENE INSOME WELLS IN THE ISTHMUS OF SUEZ AND THE NORTH-EASTERN REACH OF THE NILE DELTA, EGYPT

The lithofacies and planktic foraminiferal content of the Oligo-Miocen e interval penetrated by four wells (El-Temsah-2, Boughaz-1, Mallaha-1 X and San El-Hagar- 1) drilled in the Isthmus of Suez and in the easte rn reach of the Nile Delta enable to clarify the chronostratigraphy an d sedimentological and tectonic history of the studied sequence. The O ligocene is represented by the Qantara Formation which is conformably overlain by the Aquitanian-Burdigalian (early Miocene) Rudeis Formatio n. The early Miocene is separated from the middle Miocene (Langhian-ea rly Serravallian Kareem Formation) by a hiatus, probably reflecting th e mid-Clysmic tectonic event that affected the Gulf of Suez region. A stratigraphic gap between the early and late Serravallian Kareem and S erravallian to Tortonian Sidi Salim Formations may have been caused by the uplift of the isthmus of Suez which induced the beginning of evap orite sedimentation in restricted basins in the southern part of the G ulf of Suez. The Messinian is either represented by a regressive seque nce of coarse siliciclastics known as the Qawasim Formation or by evap orites.