Calcareous nannofossil biostratigraphy of Miocene-Pliocene sequence in the Monaga-1 Well, Nile Delta, Egypt

Abstract

The Miocene-Pliocene sequence at the Monaga-1 Well, eastern of the Nile Delta, has been examined using sixty-six ditch cutting subsurface samples, to subdivide this interval litho- and biostratigraphically based on calcareous nannofossils. Four lithostratigraphic formations and their age assignment have been recognized, organized from the highest to the lowest as follows: Kafr El-Sheikh, Abu Madi, Sidi Salem, and Qantara formations. Eight calcareous nannofossil biozones have been documented, arranged from the top to the base as follows: NN15, NN14, NN13, NN11, NN9, NN5, NN4, and NN3. The recognized biozones were compared with their respective biozones in and outside Egypt, and used to shed some light on the boundaries of the Neogene stage. Three hiatuses have been noted in the Abu Madi Formation owing to structure control as that of the depositional conditions of this formation which were tectonically unstable. Pliocene lies unconformably above the Miocene, and a small hiatus was determined where NN12 zone is missing. The Tortonian/Messinian boundary cannot be exactly determined because there is a small hiatus that is suggested by the absence of the upper NN9 zone in addition to the whole of NN10 biozones. Late Miocene overlies unconformably the Middle Miocene. This unconformity was detected by the misplaced NN6, NN7, and NN8 zones and probably the basal part of NN9 zone. At the lower boundary of the zone (NN5), the Burdigalian/Langhian boundary was drawn.