Organic Petrographic Characterization and Paleodepositional Environment of Potential Source Rocks in the Patti Formation, Bida Basin, Nigeria

Abstract

The Patti Formation in the Bida Basin, Nigeria, is a promising sedimentary sequence for hydrocarbon exploration especially the coal and shale facies in the area. This study presents an organic petrographic characterization of the coal and shale samples from the Patti Formation focusing on the palynological and biostratigraphic investigation of the rock sequence exposed within the Agbaja Patti Formation, Nigeria. This study aims to provide insight into the paleoenvironment of deposition, and age and enrich the available literature for this study area. Field observations show clearly defined coal beds within the Agbaja plateaus, occurring in association with shales and sandstones. The result of the palynological analyses of 22 selected samples shows that palynomorph recovery from the analysed samples shows abundant pollen, spore, dinoflagellates, algae, and fungal spores, especially for the coal facies. This is followed by the shale, claystone, sandy shale and ironstone in the decreasing order. The studied area is dated Early-Late Maastrichtian based on the palynomorph assemblage of Proteacidites sp., Longapertitesmarginatus, Auriculiidites reticularis, Foveotriletes margaritae, Retidiporites magdalenensis, Milfordia sp, Proteacidites longispinosus, Cingulatisporites ornatus, and Monosulcites sp., and  Syncolporites marginatus, Syncolporites subtilis, Auriculiidites reticularis, Longapertites marginatus, Proteacidites sp., Cingulatisporites ornatus, Proteacidites dehaani, Cyathidites sp., Proteacidites sigali, Crototricolpites crtonisculptus, Monosulcites sp., Longapertitites microfoveolatus, and Syncolporites lisammae. Therefore, the paleoenvironment of deposition of the investigated stratigraphic interval is composed of an admixture of terrestrially derived miospores and marine organic wall organisms of peridinacean forms, which are indicative of a marginal marine set.