Foraminiferal Biostartigraphy and Paleocology in the Late Palocene-Eocene Sequence of the Oshosun Formation Exposed Around Sagamu, Southwestern Nigeria

Abstract

Planktonic foraminiferal biostratigraphical and paleoecological studies were carried out on the Paleocene-Eocene successions exposed at the Sagamu quarry of the West African Portland Cement Company (WAPCO) southwestern Nigeria. The exposed section from the base to the top includes the Ewekoro Formation (Paleocene) which is essentially limestones and the Oshosun Formation (Late Paleocene – Early Eocene) mainly of shales. Biostratigraphy and paleoecology of foraminifera species was carried out. Twenty species of planktic and sixteen species of benthic forms were identified from the Oshosun shale interval of the section. In general, benthic species of infaunal and epifaunal habitat dominate the population. Based on the abundance and stratigraphical distribution of the planktonic foraminiferal species, two planktonic foraminiferal biostratigraphic zones were recognized, within the Oshosun Formation: a Globanomalina pseudomenardii Zone of Late Paleocene and Morosovella subbotinae Zone of Early Eocene age. Benthonic foraminifers are generally shallow marine (mostly muddy bottom dwellers). The estimated paleo-depth ranges between 50m and 150m. The environment of deposition was relatively stable during the Late Paleocene – Early Eocene times.