Palynostratigraphy, palaeoenvironments and kerogen assessment of Mid-Cretaceous Ezeaku Shales succession from River Obey in Umudi-Lokpanta, Abia State, Southeastern Nigeria

There have been disparities about the age of the Eze-Aku Formation, Anambra Basin south eastern Nigeria. Eleven surface samples of the Eze-Aku Shales from the River Obey in Umudi village, Lokpanta Abia state were subjected to standard palynological, palynofacies, kerogen preparation and analysis. A diversified palynoflora with preponderance of typical Late Cenomanian to Early Turonian diagnostic palynomorphs were recovered. Common taxa were Elaterosporites protensus, cf. Elateropollenites jardinei, Steevesipollenites binodosus, Steevesipollenites grambasti, Gnetaceaepollenites barghoornii, G. diversus, G. clathratus, Galeocornea causea, Classopollis spp., Podocarpidites herbstii, Fraxionoipollenites venustus, Cretaceaporites mulleri, Cicatricosisporites venustus, and the dinoflagellate cysts Callaiosphaeridium trycherium, Oligosphaeridium pulcherrimum, O. complex, O. albertense, Pseudoceratium pelliferum, Florentinia resex, Heterosphaeridium difficile, Surculosphaeridium longifurcatum, Cribroperidinium orthoceras and different species of Dinogymnium. Angiosperm pollens were scarce while gymnosperms were moderate due to the evolutionary trend of the flowering plants in the early Cretaceous. Structured phytoclasts with sparse amorphous organic matter which indicated deposition in nearshore to marginal marine environments dominated the palynofacies. The sporomorph colour indicated mature oil and gas generation potentials.