Micropaleontological Analysis of Rocks of Mbakwah and Environs, Gboko, Southeast Nigeria
Micropaleontological analyses of rock samples from outcrops and hand-dug wells in Gboko and its environs were carried out to better understand the geology of the area, properly delineate the various lithologies and infer the ages of the rocks. Detailed geologic mapping, micropaleontologic and petrographic methods were applied. Micropaleontological analysis involved washing and viewing of shale samples under microscope for the identification of the microfossils. The area is underlain by black shale inter-bedded with calcareous sandstone and carbonaceous limestone beds. Results of micropaleontological analysis yielded foraminifers and ostracods ranging from Cenomanian to Coniacian. Ovocytherideasymmetrica and Ovocytheridea-reniformisranges from Cenomenian to Coniacian, while Ovocytherideaashakaensis and Clithocytheridea-senegaliare indices of Turonian age. Foraminiferal analysis reveals the occurrence of benthic and planktonic index forms including Ammobaculitesjessensis, Ammobaculitesbenuensis, Whiteinellabaltica and Heterohelixreussi. The dominant arenaceous benthic foraminifers and the smooth ostracods suggests a shallow marginal marine brackish water environment. From the Shanon-Weiner Information functionfor the foraminifer’s species, H(s) value of 1.93163 was gotten and the Equitability of the specimen was calculated to be 0.69. This value implies that the species are not evenly distributed. Results of micropaleotological analysis revealed the presence of index species of foraminifers and ostracods, these showed the rocks are of Turonian age, and belong to the Ezeaku Formation.
