Biostratigraphy and Paleoenvironmental Studies of Onigbedu Sediments, Ewekoro Local Government, Ogun State.

Abstract

Abstract- Eleven (11) outcrops samples in vertical succession at the blast surface of the purechem cement mine, Onigbedu, Ewekoro from the Akinbo and Ewekoro Formationsat an interval of one meter depth were reconnoiter in order to establish the lithofacies, age and paleoenvironment. The biostratigraphic results indicated that the study area was deficient of calcareous nannofossils as well as planktonic foraminifera but benthic foraminifera were moderate to abundant in sample S2 of the Akinbo formation and samples L2, L3, L4, L5, L6, and L7 of the Ewekoro formation. Microfacies analysis carried out on three selected samples of the Ewekoro formation harmonized with already existing lithofacies classification of the Ewekoro formation as Sample L2 and Sample L4 -Biomicite, Sample L6- Biosparite. The presence of foraminifera species consisting of rare calcareous benthic, absence of Planktics and Calcareous nannofossils indicate deposition in a shallow water. Foraminiferal assemblage is characterized by Valvulineria sp, Quinqueloculina sp, Hanzawaia concentrica, Calcareous indeterminate and Ostracod suggesting sediments deposition in a marginal marine setting (Coastal Deltaic). The results of the analyses also indicate that these outcrop samples were deposited during the late Paleocene epoch, estimated numerical age of 56.8Ma to 57.3Ma and straddling the Valvulineria martinezensis Niger Delta Benthic Foraminiferal zone.