The potential of Middle Eocene to early Miocene benthic foraminifera as paleoecological indicators in the Qattara Depression, Western desert, Egypt

Abstract

A comprehensive investigation and analysis were conducted on a total of 105 benthic foraminiferal species. They were extracted from the subsurface Middle Eocene to Lower Miocene strata in the N. El Faras - 1X Well, located in the Qattara Depression of the northern Western Desert, Egypt. The stratigraphic succession primarily encompasses the upper part of the Apollonia Formation (middle to late Eocene), the Dabaa Formation (late Eocene and Oligocene), and the lower part of the Moghra Formation (Early Miocene). Paleoecological multi-proxies analysis were leveraged, including Total Foraminiferal Number (TFN), Planktonic/Benthic Ratio (%P), Species Richness (SR), Diversity Index (Fisher alpha index), Ternary plot for foraminiferal assemblage structure, Agglutinated/Calcareous Ratio (Aggl/Calc), Epifaunal/Infaunal Ratio (Ep/In), and the Trophic-Oxygen (TROX) Model.

Qualitative and quantitative analyses of the encountered benthic foraminifera, alongside CONISS cluster analysis, facilitated the delineation of five distinct clusters, each characterized by unique fossil content and paleoenvironmental attributes. Generally, the first cluster was characterized by oxic to dysoxic conditions and oligotrophic to highly oligotrophic conditions within middle to outer neritic setting. Clusters 2 and 3 were characterized by oxic to dysoxic conditions and oligotrophic to mesotrophic settings. The fourth cluster exhibited oxic to dysoxic conditions alongside mesotrophic to eutrophic conditions, and situated within a middle neritic and euphotic zone. Lastly, the fifth cluster demonstrated a gradual decrease in paleodepth within the inner neritic and euphotic zone, featuring a well oxygenated environment and mesotrophic to eutrophic conditions.