Biostratigraphy and paleoenvironment implications of the Middle Miocene-Early Pliocene succession, El-Wastani gas field, onshore Nile Delta, Egypt

In the southeastern Mediterranean of the Nile Delta, the Middle Miocene-Early Pliocene sequence was investigated biostratigraphically using calcareous nannofossil and planktonic foraminifera. Two wells were chosen from the El-Wastani gas field, onshore Nile Delta, namely, EWW1-St2 and EWE-2. The studied wells consist from older to younger four rock units: Sidi Salem, Qawasim, Abu Madi, and Kafr El-Sheikh formations, respectively. Six calcareous nannoplankton and five planktonic foraminiferal zones/subzones were discriminated. The Mediterranean zonation schemes for both calcareous nannofossil and planktonic foraminifera were conducted in this study. The calcareous nannofossil zones/subzones are from older to younger, NN6, NN10a, NN11b, NN11c, NN12b, and NN13, while the planktonic foraminiferal zones/subzones are MMi7b, MMi11, NDZ, MPl1, and MPl2. Three stage boundaries were demarcated: Serravallian/Tortonian, Tortonian/Messinian, and Messinian/Zanclean. The paleoenvironments were reconstructed based on the benthic indicator species, diversity, abundance of calcareous nannofossil and foraminifera, infaunal/epifaunal, and planktonic/benthonic ratios. Accordingly, the Middle Miocene Serravallian sediments were deposited in middle to outer neritic, whereas the Late Miocene Tortonian sediments were deposited in inner to middle neritic environments. The Late Miocene Messinian sediments were deposited under fluvio-marine and lagoonal environments that changed rapidly to upper bathyal environment by the Early Pliocene sediments.