The Mamfe Formation, South Eastern Nigeria, Its Paleoenvironments and Paleoclimatic Settings: Evidence from Petrography and Grain Size Distributions
The Mamfe formation’s sediments were analysed petrographically and texturally to identify their provenance, paleoclimate, and paleoenvironment. Sedimentological research included grain size analysis, pebble morphometry, and thin section petrography on these sediments. Grain size analysis produced average values of 0.94, 1.30, 0.1, and 1.20 for mean grain size, inclusive standard deviation, graphic skewness, and kurtosis, respectively. These findings demonstrate that the sandstones contain fine to coarse grain size representation; they are poorly sorted, with a positive skewed dominance, implying a river origin for the sediments. Bivariate analysis also reveals that fluvial processes had a significant influence on sediment transit and deposition. The elongation ratio (ER), flatness ratio (FR), maximum projection sphericity index (MPSI), oblate-prolate index (OPI), and sphericity (S) values for pebbles all fall within acceptable bounds for fluvial deposits. This shows that fluvial activities predominate during deposition. Plots of sphericity vs. OP index, as well as a triangular plot of particle form, show that the pebbles were shaped mostly by fluvial activity. According to petrographic study, feldspar and rock fragments contributed less to the sediment framework elements than quartz did. As a result, the sandstones are classified as texturally and mineralogically immature arkosic to subarkosic arenites derived from uplifted basement rocks and deposited in a humid climate.
Department of Petroleum Engineering and Geoscience Technology, Federal Polytechnic, Ekowe, Bayelsa State, Nigeria.
E. E. Okon
Department of Geology, University of Calabar, Calabar, Cross River State, Nigeria.
N. U. Essien
Department of Geosciences, Akwa Ibom State University, Mkpat Enin, Nigeria.
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