Neogene palaeoenvironments and hydrocarbon potential in the Nile Delta, Egypt: Palynological evidence from an onshore well

Abstract

Palynological organic matter (POM) of the Neogene succession from the Sidi Salim-1 well, located in the onshore Nile Delta, Egypt (Eastern Mediterranean), suggests a wide range of environments, from deltaic to offshore marine. These environments were discriminated by the overall palynofacies composition, including indicative dinoflagellate cysts, mainly Spiniferites and Selenopemphix. Near-shore marine environment was interpreted for the Middle Miocene (Langhian–Serravallian) Sidi Salim Formation. Deltaic to shallow marine environments were suggested for the Qawasim (Miocene) and Kafr El Sheikh (Pliocene) formations, while the distant (offshore) marine setting was established in the Pliocene Abu Madi Formation. This deeper environment, of the Abu Madi Formation, can be used to confirm a previous documentation of an Early Pliocene progressive drowning of an incised valley, related to the Messinian Salinity Crises (MSC) events, by the late Messinian sea level drop in the Mediterranean. Suboxic to anoxic conditions existed during deposition of the investigated well succession. Anoxia was confirmed by the occurrence of imprints of pyrite crystals across much of the well succession. The occurrence of abundant Poaceae pollen may suggest widespread dry grassland vegetation during deposition of the Neogene sediments of the well. In a regional context, the Neogene environments in the Nile Delta area vary according to the relative position of the investigated sediments, due to structural, palaeogeographic and basinal settings. The recovered palynofacies fluctuated between amorphous organic matter (AOM)-dominated and phytoclast-dominated categories, mostly of the kerogen type II, which is capable of producing oil and gas. The visual assessment of the spore coloration index (SCI) of thin-walled trilete spores in the well section, shows values ranging between 5 and 8, confirming a thermally mature organic matter and, consequently, can be potential source rocks.