Physical and Textural Characteristics of Eze–Aku Sandstone at Akpoha and Environs, Afikpo Basin, Nigeria

Year 2023, Volume: 5 Issue: 1, 39 - 50, 10.05.2023

Raphael Oaikhena Oyanyan Modestus Chijioke Ohaegbulem Chioma Elizabeth Nwaimo

Abstract

Lithofacies defined by physical and textural characteristics, lithological contacts and diagenetic features in outcrops were studied to determine the paleo–depositional processes and environments of deposition, and petrographic classification of Eze–Aku sandstone at Akpoha and Evirons. Sedimentary structures identified include hummocky and swaley cross stratifications, decalcification holes, concretions, planar cross beds, inclined parallel bedding in aggradation-progradational sandstone units, parallel laminations to wave ripple laminations and some weathering features. Six lithofacies were identified and they include laminated silty shales/shales, hummocky and swaley cross stratified fine-grained sandstones, inclined parallel bedded medium- to coarse-grained sandstones, calcareous sandstones, cross bedded medium grained sandstone and horizontal to wave-ripple laminated very fine–to fine–grained sandstone. The characteristics and associations of lithofacies show that the sandstones of Eze–Aku Formation in the study area were deposited in storm dominated shallow marine environment. The sandstones are variably indurated and thin sections analysis shows cementation and intense compaction; angular to subrounded, poor to moderately sorted and fine to coarse grains, as well as minerology of grains consisting of monocystalline quartz, feldspar, rock fragments and cement with average percentage compositions of 55-60.5, 23-26.5, 1-5, and 5-8, respectively. The sandstones were therefore classified as immature arkosic sandstones formed from sediments transported by low density fluid and sourced from plutonic rocks. The variable degrees of induration of samples from different outcrops can be attributed to variable level of compaction by overburden load or tectonic compression and possibly mild metamorphism caused by Santonian thermotectonic event.

Keywords

Eze-Aku sandstones, Sedimentary structures, Texture, Diagenetic features, Paleoenvironment

References

• Adams, A.E., Mackenzie, W.S., Guilford, C., 1988. Atlas of sedimentary rocks under microscope. ELBS Longman Group UK Ltd Publ. 107 pp.
• Akande, S.O., Egenhoff, S.O., Obaje, N.J., Erdtmann, B.D., 2011. Stratigraphic Evolution and Petroleum Potential of Middle Cretaceous Sediments in the Lower and Middle Benue Trough, Nigeria: Insights from New Source Rock Facies Evaluation. Petroleum Technology Development Journal 1, 1-34.
• Akpofure, E., Didei, I., 2018. Sedimentology of the Turonian Eze-Aku Sandstone in the Afikpo Basin, Nigeria. International Journal Geology and Mining 4(2), 211-223.
• Amajor, L.C., 1987. The Eze-Aku Sandstone ridge (Turonian) of southeastern Nigeria: a re-interpretation of their depositional origin. Nigerian Journal of Mining and Geology 23 (1-), 17-26.
• Brice, S.E., Cochran, M.D., Pardo, G., Edwards, A.D., 1982. Tectonics and sedimentation of the south Atlantic rift sequence, Cabinda, Angola, In: J.S. Watkins and C.L. Drake (eds. Studies in continental margin geology. AAPG Memoir 34, 5-18.
• Burke, K.C.,1970. Geological history of the Benue valley and adjacent areas. (Ed) African Geology university of Ibadan press, Ibadan, pp. 187-202.
• Burley, S.D., Richard H., Worden, R.H., 2003. Sandstone Diagenesis: The evolution of sand to stone, In sandstone diagenesis: Recent and Ancient. International Association of Sedimentologists, pp. 3- 44. ISBN: 978-1-405-10897-3
• Catuneanu, O. 2006. Principles of Sequence Stratigraphy. Elsevier B.V. publ., 387 pp.
• Gingras, M.K., Bann, L., MacEachern, J. A., Pemberton, G., 2007. A Conceptual Framework for the Application of Trace Fossils. In: MacEachern, J.A., Bann, K.L., Gingras, M.K., Pemberton, S.G. (Eds.), Applied Ichnology, SEPM, Tulsa, ISBN-10: 1565761332, pp.1-26.
• Glossary of Terms in Soil Science, 1976. Ottawa Agriculture, Canada, 13pp. ISBN 0662015339.
• Marshall, J.D, Pirrie, D., 2013. Carbonate concretions –Explained. Geology today 29 (2).
• Murat, R.C., 1972. Stratigraphy and paleogeography of the Cretaceous and lower Tertiary in southern Nigeria. In: Dessauvagie, T.F.J. and Whiteman, A.J. (eds), African Geology, University of Ibadan Press, Nigeria, pp. 251- 266.
• Nichols, G., 2009. Sedimentology and Stratigraphy. Wiley and Blackwell Publ. (second edition), 432pp.
• Odigi, M.I., Amajor, L.C., 2008. Petrology and Geochemistry of Sandstones in the Southern Benue Trough of Nigeria: Implications to Provenance and Tectonic Setting. Chinese Journal of Geochemistry 27 (4), 384-394.
• Ojo, O.J., Ajibola, U.K., Akande, S.O., 2009. Depositional environments, organic richness petroleum generating potential of the Campanian to Maastrichtian Enugu formation, Anambra Basin, Nigeria. Pacific Journal Science Technology 10, 614-628.
• Oyanyan, R.O., Oti, M.N., 2015. Sedimentology and Ichnology of Late Oligocene Delta Front Reservoir Sandstone Deposit, Greater Ughelli Depobelt, Niger Delta. American Journal of Geosciences 5 (1), 12-25. Doi: 10.3844/ajgsp.2015.12.25.
• Pettijohn, F.J., 1975. Sedimentary Rocks, 3rd edn.: Harper and Row, New York, NY., 718 pp.
• Reading, H.G., Collinson, J.D.,1996. Clastic coasts. In: Reading, H. G.(ed) Sedimentary Environments: Processes, Facies and Stratigraphy, Blackwell Science publ., pp. 154-231.
• Reijers, T. J. A., Peters, S. W., Nwajide, C. S., 1997. The Niger delta Basin, in African Basins. In: Selly, R.C. (eds), Sedimentary Basins of the world, Elsevier Publ., 3, pp 151 -172.
• Reyment, R.A., 1965. Aspects of the Geology of Nigeria. Ibadan University Press, Ibadan. 145 pp.
• Selley, R.C., 1985. Ancient Sedimentary Environment and their sub-surface diagnosis. Chapman and Hall Publications, 11 New Fetter lane, London, 318 pp.
• Selly, R.C., 2000. Applied Sedimentology (second edition). Academic press publication. 543 p.
• Stubblefield, W.L., McGrail, D.W., Kersey, D.G., 1984. Recognition of transgressive and post-transgressive sand ridges on the New Jersey continental shelf. In: Tillman, R.W., Siemers, C.T Siliciclastic Shelf Sediments (eds.). Special Publication 34, SEPM (Society for Sedimentary Geology), Tulsa, OK, pp.1-23.
• Swift, D.J.P., Figueiredo, A.G. Freeland, G.L., Oertel, G.F., 1983. Hummocky cross-stratification and mega ripples: a geological double standard. Journal of Sedimentary Petrology 53, 1295-1317.
• Tucker, M.E., 2003. Sedimentary Rocks in the Field (3rd edition). Wiley publ., Chichester, 249 pp.
• Tucker, M.E., Wright, V.P., 1990. Carbonate Sedimentology. Blackwell Scientific Publications, Oxford, 482 pp.
• Ukaegbu, V.U., Akpabio, I. O., 2009. Geology and Stratigraphy of Middle Cretaceous Sequences Northeast of Afikpo Basin, Lower Benue Trough, Nigeria. Pacific Journal of Science and Technology 10 (1), 518 – 527.
• Whiteman, A., 1982. Nigeria: Its Petroleum Geology, Resources and Potentials. Vol. 1 & 2. Graham and Trotman Ltd.: London. UK.
• Worden, R. H., Burley, S.D., 2003. Sandstone Diagenesis: The evolution of sand to stone, In Burley, S. D., Richard H. and Worden, R. H. (Eds). Sandstone diagenesis: Recent and Ancient. International Association of Sedimentologists, pp. 3- 44. ISBN: 978-1-405-10897-3.