Geochemical Constraints on Provenance, Paleoweathering, And Paleodepositional Conditions of The Mamu Formation Along Apana–Imiegba Road, Western Anambra Basin, Nigeria
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Keywords:
Mamu Formation, Anambra Basin, sediment geochemistry, provenance, paleoweathering, paleoenvironmental reconstructionAbstract
The Late Cretaceous Mamu Formation in the western Anambra Basin consists of transitional deltaic to shallow marine deposits that record changes in sediment source, weathering, salinity, redox conditions, and depositional processes. This study uses major and trace element geochemistry of outcrop samples collected along the Apana–Imiegba road to assess provenance, paleoweathering, and paleodepositional conditions. Major-element indices, including CIA, PIA, and CIW, indicate strong chemical weathering of the source area, consistent with warm and humid paleoclimatic conditions. Provenance-sensitive ratios such as Al₂O₃/TiO₂ and Fe₂O₃/TiO₂ suggest derivation mainly from felsic continental source rocks, with limited evidence of sediment recycling. Trace element ratios, including Sr/Ba and Sr/Cu, point to fluctuating brackish to marginal marine conditions, while redox-sensitive proxies such as V/Cr, U/Th, and Cu/Zn indicate suboxic to weakly anoxic bottom-water conditions, especially in shale-rich intervals. Relative enrichment in phosphorus and barium, together with higher P/Ti values in some intervals, may indicate episodic productivity under favorable preservation conditions. Overall, the Mamu Formation along the Apana–Imiegba road reflects deposition in a humid, delta-influenced basin marked by variable salinity, fluctuating redox conditions, and mixed continental to marginal marine influence.
References
[1] Tribovillard, N., Algeo, T. J., Lyons, T. W., & Riboulleau, A. (2006). Trace metals as paleoredox and paleoproductivity proxies: An update. Chemi-cal Geology, 232, 12–32. https://doi.org/10.1016/j.chemgeo.2006.02.012.
[2] Zhang, K., Liu, R., Liu, Z., Li, L., Wu, X., & Zhao, K. (2020). Influence of palaeoclimate and hydrothermal activity on organic matter accumulation in lacustrine black shales of the Lower Cretaceous Bayingebi Formation, Yin’e Basin, China. Palaeogeography, Palaeoclimatology, Palaeoecology, 560, 110007. https://doi.org/10.1016/j.palaeo.2020.110007.
[3] Nesbitt, H. W., & Young, G. M. (1982). Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature, 299, 715–717. https://doi.org/10.1038/299715a0.
[4] Harnois, L. (1988). The CIW index: A new chemical index of weathering. Sedimentary Geology, 55, 319–322. https://doi.org/10.1016/0037-0738(88)90137-6.
[5] Fedo, C. M., Nesbitt, H. W., & Young, G. M. (1995). Unravelling the effects of potassium metasomatism in sedimentary rocks and paleosols: Impli-cations for paleoweathering conditions and provenance. Geology, 23, 921–924. https://doi.org/10.1130/0091-7613(1995)023<0921:UTEOPM>2.3.CO;2.
View more references (26)
[6] Rimmer, S. M. (2004). Geochemical paleoredox indicators in Devonian–Mississippian black shales, Central Appalachian Basin (USA). Chemical Geology, 206, 373–391. https://doi.org/10.1016/j.chemgeo.2003.12.029.
[7] Goldberg, K., & Humayun, M. (2016). Geochemical paleoredox indicators in organic-rich shales of the Irati Formation, Permian of the Paraná Basin, southern Brazil. Brazilian Journal of Geology, 46, 377–393. https://doi.org/10.1590/2317-4889201620160001.
[8] Reyment, R. A. (1965). Aspects of the geology of Nigeria: The stratigraphy of the Cretaceous and Cenozoic deposits. University of Ibadan Press.
[9] Obi, C. G., Okogbue, C. O., & Nwajide, C. S. (2000). Evolution of the Enugu Cuesta: A tectonically driven erosional process. Global Journal of Pure and Applied Sciences, 7, 321–330. https://doi.org/10.4314/gjpas.v7i2.16251.
[10] Murat, R. C. (1972). Stratigraphy and paleogeography of the Cretaceous and Lower Tertiary in southern Nigeria. In T. F. J. Dessauvagie & A. J. Whiteman (Eds.), African geology (pp. 251–266). University of Ibadan Press.
[11] Nwajide, C. S., & Reijers, T. J. (1996). Geology of the southern Anambra Basin. In Selected chapters on geology: Sedimentary geology and se-quence stratigraphy in Nigeria and three case studies.
[12] Petters, S. W. (1991). Stratigraphic evolution of the Benue Trough and its implication for Upper Cretaceous palaeogeography of West Africa. Journal of Geology, 86, 311–322. https://doi.org/10.1086/649693.
[13] Dim, C., Okogbue, C. O., Umeji, A., Okeugo, C., & Ogah, J. (2013). Sequence stratigraphy and petroleum potential of Cretaceous strata in the Anambra Basin, southeastern Nigeria. Journal of Geology Research, 61, 1–10.
[14] Akinyemi, S., Adebayo, O., Ojo, O., Fadipe, O., & Gitari, W. (2013). Mineralogy and geochemical appraisal of paleo-redox indicators in Maastrichti-an outcrop shales of the Mamu Formation, Anambra Basin, Nigeria. Journal of Natural Sciences Research, 3, 48–64.
[15] Okiotor, M. E., & Ighodaro, E. J. (2020). Geochemical appraisal of the Mamu Shales exposed around Igodor in the Benin Flank of the Anambra Ba-sin, Nigeria. Journal of Applied Sciences and Environmental Management, 24, 489–493. https://doi.org/10.4314/jasem.v24i3.15.
[16] Jayeola, A. O., Oluwajana, O. A., Olatunji, O. A., Udofia, M. U., & Danjuma, O. (2016). Sedimentological, palynological, and foraminiferal biostrat-igraphic studies of the Upper Cretaceous Mamu Formation at Imiegba, Anambra Basin, Edo State, Nigeria. Achievers Journal of Scientific Research, 1, 37–56.
[17] Akande, S. O., & Mücke, A. (1993). Mineralogy, petrography, and genesis of some Nigerian coals. International Journal of Coal Geology, 23, 93–115.
[18] Dim, C.I.P., Mode, A.W. & Okwara, I.C. Signatures of key petroleum system elements: outcrop examples from the Anambra Basin, Southeastern Nigeria. J Petrol Explor Prod Technol 9, 1615–1631 (2019). https://doi.org/10.1007/s13202-018-0589-2.
[19] Edegbai, A., Oboh-Ikuenobe, F. E., & Obi, C. G. (2019a). Palynofacies and paleoenvironmental interpretation of Upper Cretaceous sediments from the Anambra Basin, southeastern Nigeria. Journal of African Earth Sciences, 150, 727–744.
[20] Tijani, M. N., Onodera, S., & Adeleye, M. A. (2010). Hydrochemical and stable isotope assessment of groundwater quality in a basement complex terrain, southwestern Nigeria. Hydrogeology Journal, 18, 453–470.
[21] Mode, A. W., & Odumodu, C. F. R. (2015). Lithofacies and ichnology of the Late Maastrichtian–Danian Nsukka Formation in the Okigwe area, Anambra Basin, southeastern Nigeria. Arabian Journal of Geosciences, 8, 7455–7466. https://doi.org/10.1007/s12517-014-1742-y.
[22] Obaje, N. G. (2009). Geology and mineral resources of Nigeria. Springer. https://doi.org/10.1007/978-3-540-92685-6.
[23] Nwajide, C. S. (2005). Anambra Basin of Nigeria: Synoptic basin analysis as a basis for evaluation of hydrocarbon prospectivity. In C. O. Okogbue (Ed.), Hydrocarbon potentials of the Anambra Basin (pp. 2–46). Great AP Express Publishers.
[24] Loubser, M., & Verryn, S. (2008). An evaluation of some South African Permian coals by organic petrology, geochemistry and FTIR spectroscopy. International Journal of Coal Geology, 75, 1–14.
[25] Hayashi, K.-I., Fujisawa, H., Holland, H. D., & Ohmoto, H. (1997). Geochemistry of ~1.9 Ga sedimentary rocks from northeastern Labrador, Cana-da. Geochimica et Cosmochimica Acta, 61, 4115–4137. https://doi.org/10.1016/S0016-7037(97)00214-7.
[26] Scotese, C. R., Song, H., Mills, B. J. W., & van der Meer, D. G. (2021). Phanerozoic paleotemperatures: The Earth’s changing climate during the last 540 million years. Earth-Science Reviews, 215, 103503. https://doi.org/10.1016/j.earscirev.2021.103503.
[27] Jones, B., & Manning, D. A. C. (1994). Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mud-stones. Chemical Geology, 111, 111–129. https://doi.org/10.1016/0009-2541(94)90085-X.
[28] Wignall, P. B., & Maynard, J. R. (1993). The sequence stratigraphy of transgressive black shales. In B. J. Katz & L. M. Pratt (Eds.), Source rocks in a sequence stratigraphic framework (pp. 35–47). AAPG Studies in Geology. https://doi.org/10.1306/St37575C4.
[29] Li, D., Li, R., Zhu, Z., Wu, X., Liu, F., Zhao, B., Cheng, J., & Wang, B. (2018). Elemental characteristics and paleoenvironment reconstruction: A case study of the Triassic lacustrine Zhangjiatan oil shale, southern Ordos Basin, China. Acta Geochimica, 37, 134–150. https://doi.org/10.1007/s11631-017-0193-z.
[30] Dymond, J., Suess, E., & Lyle, M. (1992). Barium in deep-sea sediment: A geochemical proxy for paleoproductivity. Paleoceanography, 7, 163–181. https://doi.org/10.1029/92PA00181.
[31] Obi, C. G. (2000). Depositional model for the Campanian–Maastrichtian Anambra Basin, southeastern Nigeria [Doctoral dissertation, University of Nigeria, Nsukka].