Quantitative calcareous nannofossil biostratigraphy of the subsurface Pliocene sequence,north-east Nile Delta,Egypt

Detailed quantitative calcareous nannofossil biostratigraphy was carried out on a subsurface lower–upper Pliocene succession (Kafr El Sheikh Formation) in three offshore wells (Ras El Barr-1, Bougaz-1 and Bougaz East-1), north-east Nile Delta area, Egypt. The standard zonations are easily applied in these sediments and additional biohorizons have been adopted in this study. For early to late Pliocene interval, the following five bioevents are considered reliable: last occurrences (LOs) of Discoaster surculus, D. tamalis, Reticulofenestra pseudoumbilicus and Amaurolithus tricorniculatus and first occurrence of D. asymmetricus. The LO of R. pseudoumbilicus was used to detect the early/late Pliocene boundary in the three studied wells. In Bougaz-1-Well, the LO of D. intercalcaris was used to approximate the Miocene/Pliocene boundary. The calcareous nannofossils are moderate to good preserved. Lower–upper Pliocene sediments are dominated by small-sized reticulofenestrids (R. minuta), Pseudoemiliania lacunosa, Helicosphaera carteri and H. kamptneri. Large size (>7 μm) R. pseudoumbilicus is recorded. Discoaster species is rarely represented. No nannofossils were found in the top part of the Kafr El Sheikh and the overlying Wastani Formations.