Diagenetic Effects on Foraminifera Preservation and Paleoenvironmental Interpretation in Well-T, Anambra Basin, Nigeria
Abstract
This study investigates diagenetic effects on foraminiferal preservation and their implications for paleoenvironmental reconstruction in Well-T, Anambra Basin, southeastern Nigeria. Analysis of ditch cuttings, intervals 165-1097m spanning the Nsukka Formation (165-622m) and Ajali Formation (6221097m) revealed significant lithofacies-controlled preservation patterns. The Nsukka Formation yielded mixed calcareous and agglutinated assemblages with moderate preservation, while the Ajali Formation contained exclusively agglutinated foraminifera due to complete calcite dissolution. Diagenetic processes including dissolution, recrystallization, overgrowth, and ferruginisation were identified as primary controls on microfossil integrity. The study demonstrates that fine-grained, less permeable shales provide better preservation environments than coarse-grained sandstones. Despite diagenetic alteration, meaningful paleoenvironmental interpretations were derived, indicating a transition from fluvial-deltaic (Ajali Formation) to shallow marine conditions (Nsukka Formation) during Late Cretaceous to Early Paleocene.
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Riferimenti bibliografici
Abdulkareem, T., Omotolani, I. F., N’Guessan, F. D. S., & Adekeye, O. (2025). New insights into the geochemical characteristics of petroleum source rocks and oils from southern Nigerian sedimentary basins. Journal of Petroleum Geology, 48(4), 280–306.
Abubakar, M. B. (2014). Petroleum potentials of the Nigerian Benue Trough and Anambra Basin: A regional synthesis. Natural Resources, 5(2), 25–58.
Adeagbo, O. A. (2010). Petroleum potential of Campano-Maastrichtian shales of Anambra Basin, southeastern Nigeria. Global Journal of Geological Sciences, 8(1), 43–52.
Andaye, A., Okoro, A. U., & Nwankwo, C. N. (2025). Paleoenvironment, paleoredox and paleogeography of Mamu Shale, Anambra Basin, southern Nigeria. Achievers Journal of Scientific Research, 7(1), 1–18.
Bertram, C. J., & Elderfield, H. (1993). Diagenetic alteration of planktonic foraminiferal assemblages. Marine Geology, 113(4), 287–301.
Choquette, P. W., & Pray, L. C. (1970). Geologic nomenclature and classification of porosity in sedimentary carbonates. Bulletin of the American Association of Petroleum Geologists, 54, 207–250.
Dim, C. I. P., Onuoha, K. M., Okeugo, C. G., & Ozumba, B. M. (2017). Petroleum system elements within the Late Cretaceous and early Paleogene sediments of Nigeria's inland basins: An integrated sequence stratigraphic approach. Journal of African Earth Sciences, 130, 76–86.
Drinia, H., Antonarakou, A., & Zachariasse, W. J. (2007). Taphonomic alterations in benthic foraminifera. Micropaleontology, 53(6), 511–522.
Edegbai, A. J., & Emofurieta, W. O. (2020). Hydrocarbon generation potential of the Campano-Maastrichtian dark mudstone lithofacies, Benin Flank, South West Anambra Basin, Nigeria. Journal of Applied Sciences and Environmental Management, 24(11), 1889–1897.
Epuh, E., Obi, D. A., Nwankwo, L. I., & Onwuemesi, A. G. (2025). Implications of gravity derivative filters and residual geoid on crustal deformations in the Anambra Basin, southeast Nigeria. Journal of African Earth Sciences, 221, 105196. https://doi.org/10.1016/j.jafrearsci.2025.105196
Etu-Efeotor, J. O., & Akpobasah, D. E. (1996). Petroleum geology of the Anambra Basin, Nigeria. Journal of Mining and Geology, 32(2), 47–58.
Kontakiotis, G., Avramidis, P., & Piper, D. J. W. (2011). Diagenetic impact on benthic foraminiferal assemblages: Implications for paleoenvironmental analysis. Journal of Foraminiferal Research, 41(4), 303–320.
Marshak, S. (2009). Essentials of Geology (3rd ed.). W. W. Norton & Company.
Milliken, K. L. (2014). Late diagenesis and mass transfer in sandstone–shale sequences. In H. D. Holland & K. K. Turekian (Eds.), Treatise on Geochemistry (2nd ed., Vol. 7, pp. 181–206). Elsevier.
Murray, J. W. (2006). Ecology and Applications of Benthic Foraminifera. Cambridge University Press.
Njoku, J. O., Nwajide, C. S., Onyekuru, S. O., & Obi, G. C. (2025). Biostratigraphic and sequence stratigraphic study of the Late Cretaceous–Paleogene succession in the Anambra Basin, southeastern Nigeria: Insights from the Amama-1 and Bara-1 wells. Journal of African Earth Sciences, 219, 105143.
Nwajide, C. S. (2005). Anambra Basin of Nigeria: Synoptic basin analysis as a basis for evaluating its hydrocarbon prospectivity. In C. O. Okogbue (Ed.), Hydrocarbon Potentials of the Anambra Basin: Geology, Geochemistry and Geohistory Perspectives (pp. 1–46). Proceedings of the first seminar organized by the Petroleum Technology Development Fund (PTDF) Chair in Geology, University of Nigeria.
Obi, G. C., Nwajide, C. S., & Okogbue, C. O. (2001). Lithostratigraphy and depositional environments of the Campanian–Maastrichtian sediments in the Anambra Basin. Global Journal of Geological Sciences, 1(1), 51–62.
Okogbue, C. O., & Aghamelu, O. P. (2010). Geomechanical and geochemical characteristics of Anambra Basin shales: Implications for seal integrity. Journal of African Earth Sciences, 58(1), 47–61.
Okunlola, O., Agonsi Udodirim, L., Umaru, A. O., Kazapoe, R. W., & Olisa, O. G. (2023). Mineralogy and geochemistry of shale deposits in the Lower Anambra Basin, Nigeria: Implication for provenance, tectonic setting and depositional environment. Economic and Environmental Geology, 56(6), 799–816.
Petters, S. W. (1976). The marine Maastrichtian and Paleocene sediments of north-western Nigeria. In Geological Guidebook of the 7th African Micropaleontological Colloquium (pp. 75–87). Ile-Ife.
Reolid, M., Molina, J. M., & Rodríguez-Tovar, F. J. (2008). Diagenetic impact on benthic foraminiferal assemblages: Paleoenvironmental implications from the Jurassic. Facies, 54(4), 513–529.
Reyment, R. A. (1965). Aspects of the Geology of Nigeria. Ibadan University Press.
Tijani, M. N., Nton, M. E., & Kitagawa, R. (2010). Textural and geochemical characteristics of the Ajali Sandstone, Anambra Basin, SE Nigeria: Implication for its provenance. Comptes Rendus Géoscience, 342(2), 136–150.
Umeji, A. C. (2003). Foraminiferal biostratigraphy and paleoecology of Nkporo Shale in Anambra Basin. NAPE Bulletin, 16(1), 25–35.
