Palynofacies and Kerogen Analyses of Upper Cretaceous (Campanian-Danian) Shales of Ugwueme Section of Anambra Basin, Southeastern Nigeria

Three samples of shale recovered from late Campanian to Danian sediments around Ugwueme area, Anambra Basin were studied for their particulate organic matter distribution and hydrocarbon potentials. Two major palynofacies were identified and designated palynofacies A and palynofacies B. Palynofacies A occupies the basal unit (Nkwe mudstone unit of Nkporo Shale) and the topmost unit; Umuaku shale unit of Nsukka Formation).Palynofacies A is dominated by abundant amorphous organic matter (AOM) and some phytoclastmaterials majorly of macerol marine exinite and some terrestrial influenced materials. Palynofacies B represents the middle unit bed (AcharaUgwueme shale unit of Mamu Formation) constitutes abundant phytoclasts with opaque debris of well-preserved terrestrial influenced plant fragments. The kerogen investigation result shows Nkwe mudstone unit of Nkporo Shale Formation and Umuaku shale unit of Nsukka Formation to be type II/III kerogens known to be oil-gas prone material. The study reveals that AcharaUgwueme shale unit of Mamu Formation is of type III kerogen known to be gas-prone. Estimation of the maturation stage of the samples using the exinecolours of pale-yellow to yellow, the sporomorphs shows (1+ to 2+)thermal alteration index(TAI) and reflectance values of 0.3% for both Nkwe mudstone and AcharaUgwume shale unit, thus are thermally immature to generate hydrocarbons while Umuaku shale unit with exinesporomorphscolour of yellow –light brown, (2to2+), thermal alteration index (TAI) and reflectance value of 0.5% to be thermally immature to early mature (early oil phase of hydrocarbon generation).