Lithofacies, Palynostratigraphy and Paleoecology of the Outcropping Rock Succession at Ogbunike Old Toll Gate, Niger Delta Basin, Nigeria

Abstract

Aim: Sedimentary succession exposed at Ogbunike old toll gate is part of the outcropping sediments of the Niger Delta Basin and its age is controversial. The outcrop was studied for the purpose of age determination, lithostratigraphic placement and interpretation of paleoecology, paleoclimatology and depositional environment.
 Methodology: Lithofacies and biofacies analyses were integrated in the study.
 Results: Thirteen lithofacies identified include; bioturbated sandstone, ripple laminated sandstone, ripple laminated claystone, dark shale, ferruginized sandstone, carbonaceous sandstone, greyish shale, very fine sandstone, mudstone, massive claystone, coarse sandstone, cross bedded sandstone and flaser bedded sandstone lithofacies. Four lithofacies associations consisting of lower shoreface to inner neritic, fluvial channel, lagoonal/mixed flat and subtidal sandwave associations were delineated. Middle Eocene age is assigned to the succession based on the high abundance of marker pollen such as Margocolporites foveolatus, Ctenelophonidites costatus, Monocolpites marginatus, Retibrevitricolporites triangulatus, Proxapertites cursus, Bombacacidites sp. and common occurrences of Scrabratisporites simpliformis, Anacolosidites luteoides, Psilatricolporites crassus, Gabonisporis viaourouxii, Striatricolporites catatumbus and Retistephanocolporites williamsi. These co-occur with Cordosphaeridium cantharellus. Palynofloral group recovered are dominated by mangrove and palm pollen. Pteridophyte spores are also abundant whereas the hinterland pollen group is very low. Benthic foraminiferal assemblages of Textularia, Miliammina,Ammobaculites Haplophragmoides, Fursenkoina, Heterolepa, Reophax, Nodosaria, Florilus, Uvigerina, Cibicides and Bolivina recovered from the dark shale suggest deposition in an inner neritic setting. Trace fossil suite of Skolithos- Cruziana ichnofacies is an attribute of the sedimentary units.
 Conclusion: The sedimentary succession is part of the Ameki Group (Nanka Formation) deposited under varied environmental setting. Paleoclimate is tropical.