PETROGRAPHIC AND PALYNOLOGICAL ANALYSES OF THE EZE-AKU GROUP IN AKPOHA AND ENVIRONS, SOUTHERN BENUE TROUGH, NIGERIA

Cretaceous sediments outcropped extensively in the Abakaliki sedimentary basin.Petrographic and palynological analyses of selected outcrop samples from Akpoha and environs were carried out, using the conventional method of acid macerationin order to re-establish the depositional history of the sediments in the area and their provenance, establish the age of sediments and reconstruct their paleoenvironments of deposition, and evaluate the hydrocarbon source rock potential. Lithological units encountered include sandstones, shales, mudstones, and limestone. Result from sandstone petrography shows that most of the sandstones in the area were mostly derived from the metamorphic /igneous basement sources, and were deposited in a very low energy environments where sediments are rapidly deposited with little reworking. Palynological investigation revealed a Late Cenomanian Middle Turonian age for the sediments, with the following index sporomorph assemblage: Cretacaeiporitesscabratus, Ephedripitesmulticostatus, Cretacaeiporitesmulleri, Monosulcites sp., Tricolporopollenites sp. and Tricolpites sp. Palynomorphs of environmental value indicated that the sediments in the area were mostly deposited under openmarine condition, with minor terrigenous input. Kerogen examination features mostly the amorphous organic matter (AOM), followed by opaque debris, giving rise to type 11 / type 111 kerogen, which are generally over mature but have potential to generate oil or gas.

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