Middle to late Eocene <i>Nummulites</i> from the southern Tethys, Fayum, Egypt: taxonomic, biostratigraphic, and paleobiogeographic context

Abstract The present paper focuses on the middle to late Eocene Nummulites from the southern margin of the Tethys Ocean to address gaps in taxonomy of Nummulites , with emphasis on their biostratigraphic implications and paleobiogeographic distributions. Integration of biometric and morphological data with other taxonomic characters is used to define four Nummulites species ( Nummulites midawaraensis Kenawy, 1978 , N. biarritzensis d’Archiac and Haime, 1853 , N. lyelli d’Archiac and Haime, 1853, and N. striatus (Bruguière, [1792]) from Fayum, Egypt. Biostratigraphically, three main biozones are identified. The Nummulites midawaraensis Biozone characterizes the Lutetian Midawara Formation. The N. lyelli Biozone heralds the Bartonian El-Gharaq Formation. The uppermost Priabonian Stage is demarcated by the N. striatus Biozone within the Birket Qarun Formation. These biozones match well with the Lutetian to Priabonian Tethyan larger benthic foraminiferal biozones. Distinct temporal changes and geographic distributions of the Nummulites assemblages distinguish remarkable middle to late Eocene paleobiogeographic provinces within the Tethys Ocean. Nummulites midawaraensis is probably endemic to the Egyptian southern Tethys Ocean, whereas the N. biarritzensis , N. lyelli , and N. striatus flourished throughout the Tethyan Realm, extending eastward from Spain to Pakistan and India. Notably, our findings strengthen the evidence for a strong connection between the Indo-Pakistani and Tethyan provinces during the Eocene. The relatively warm events throughout the middle to late Eocene led to an active carbonate factory and flourishing of calcite tests of Nummulites that favored clear waters and light under tropical to subtropical shallow-marine conditions.