Biogeographic and bathymetric distribution of benthic foraminifera in Paleocene El Haria Formation of Tunisia

Abstract

Qualitative and quantitative analysis of benthic foraminiferal fauna reveals the succession of five benthic assemblages in the Paleocene El Haria Formation of El Kef section (Tunisia). The eugubina Zone is characterized by Anomalinoides acuta, A. praecuta, Cibicidoides alleni, C. susanaensis and Bulimina quadrata, developed in a bathyal environment of relatively low oxygen conditions. The pseudobulloides Zone presents a “Velasco-type” fauna, with Gavelinella beccariiformis, Osangularia plummerae, Cibicidoides alleni, C. susanaensis, N. truempyi and textulariids. Microfauna suggests an oxic environment in the upper bathyal stage. A regressive sea movement becomes perceptible and benthic fauna indicates an outer shelf paleobathymetry during the interval comprised between the trinidadensis and the pusilla Zones. The assemblage, developed in oxic conditions, is characterized by Alabamina midwayensis, Anomalinoides praeacuta and Cibicidoides susanaensis. The fourth assemblage, observed during the pseudomenardii and velascoensis (lower part) Zones, is typical of the continental shelf (middle to inner neritic; “Midway-type” fauna) with Alabamina midwayensis, Eponides elevatus, Anomalinoides midwayensis, buliminids and lenticulinids. The upper part of the section (velascoensis Zone) presents an inner neritic assemblage dominated by Stainforthia troosteri, Haplophragmoides excavata, Eponides elevatus and lenticulinids.

These El Kef data are compared with Paleocene foraminiferal data of field sections of central and southern Tunisia. Statistical analysis (correspondence analysis) confirms the lowering of the sea level from the K/T boundary to Early Eocene and indicates precisely the paleogeographic scheme of the Paleocene deposits of Tunisia, with the restricted Gulf of Gafsa in the south, the emerged island of Kasserine in the west and an unstable shelf cut up into deep basins in the east and in the north.