Integrated biostratigraphy of the upper Oligocene-middle Miocene successions in west central Sinai, Egypt

The nannofossil and planktonic foraminiferal biostratigraphy in four upper Oligocene-middle Miocene sections are examined in Nukhul-Sudr area of west central Sinai, Egypt. The integration of calcareous nannofossils and planktonic foraminifera is used to verify the ages and determine the biozones of the upper Oligocene-middle Miocene units in the studied area. This target is important in the light of the great lithofacies changes during the time interval. The detailed examination of the nannofossil and planktonic foraminiferal contents in these sections led to identification of 86 calcareous nannofossil species belonging to 22 genera, 10 families and 3 orders, in addition to 64 planktonic foraminiferal species belonging to 11 genera, 4 families and 2 superfamilies. The identified nannofossil and planktonic foraminiferal assemblages allow to distinguish five calcareous nannofossil biozones and six planktonic foraminiferal biozones. The biostratigraphic integration suggested the Chattian-Aquitanian age for the Nukhul Formation where the Globigerina ciperoensis Zone (P22) and Globigerinoides primordius Zone (M1a) correspond to calcareous nannofossil Sphenolithus ciperoensis Zone (NP25) and Discoaster druggii Zone (NN2), respectively. The Rudeis Formation is assigned to the Burdigalian-Langhian age depending on correspondence of Catpsydrax dissimilis Zone (M2), Globigerinoides bisphericus Zone (M4b) and Praeorbulina sicana Zone (M5) with Discoaster druggii zone (NN2), Sphenolithus belemnos Zone (NN3) and Helicosphaera ampliaperta Zone (NN4). The Somar Formation is found barren ofany microfossils, but it contains index pectens and oysters of Burdigalian age which may be equivalent to the lower part of the Rudeis Formation. The Kareem and Sarbut El-Gamal formations are represented by evaporitic and conglomeratic succession, where no foraminifera or nannofossils are recorded and assigned to the Langhian age according to their stratigraphic position. The Belayim Formation is assigned to the Serravallian age, due to the presence of Globorotalia fohsi Zone (M8) which equivalent to Discoaster exilis Zone (NN6).