MORPHOMETRIC ANALYSIS OF GRAVELS FROM THE BENIN FORMATION, NIGER DELTA BASIN, NIGERIA

ABSTRACT

One hundred and fifty (150) gravel samples collected from gravel facies and gravelly horizons in sand quarry sites at Okhoro, Evbuomore, and Idumwowina localities in Benin City Edo State, Nigeria were subjected to gravel morphometric analysis in order to determine the environment of deposition.. The mean values of flatness Index (FI), elongation ratio (ER), Maximum projection sphericity (MPS) and Oblate – prolate index for each location were : Okhoro: 0.45, ( ER) 0.66, (MPS) 0.67, (OPI) 3.11. Location 2: (FI) 0.59 ( ER) 0.68, (MPS) of 0.799 (OPI) 5.04. Evbuomore: (FI) 0.51 ( ER) 0.66, (MPS) 0.73, (OPI) 4.19. Idumwowina: (FI) 0.52, ( ER) 0.68, (MPS) 0.73, (OPI) 3.27. Evbuomore : (FI) 0.55 ( ER) 0.71, (MPS) 0.75, (OPI) 2.51.In addition, bivariate plots of Maximum projection sphericity (MPS) and Oblate – prolate index as well as Maximum projection sphericity (MPS) and coefficient of flatness suggest a predominant fluvial paleoenvironment with minor and under 25% falling within a marine influence. Therefore, this study shows that the Benin Formation formed was deposited under fluvial depositional conditions with some marine influence.