Granulometry and pebble morphometry of an exposed section of the Benin Formation around Okurikang and environs, Southeastern Nigeria. – D. O.Inyang,A.E. Itam and E.E. Okon
Grain size analysis and pebble morphometry was carried out in parts of Benin Formation exposed along Okurikang and its environs in the northwestern part of the Calabar Flank to determine the depositional environment. Granulometric analysis of 12 samples revealed that the studied section was predominantly coarse grained having graphic mean (MZ) of 1.23ϕ, average sorting coefficient (σI) of 1.61ϕ. The sediments were positively skewed (Ski averages 0.29) and ranged from platykurtic to being leptokurtic (KG mean of 1.12). Pebble morphometric analysis of the conglomerates (600 pebbles) from 20 different locations showed that the mean values of various morphometric ranges as follows: flatness ratio (FR = 0.23-0.52), flatness index (FI=23% to 52%), elongation ratio (ER =0.52-0.73), maximum projection sphericity (MPSI = 0.28-0.73) and oblate prolate index (OPI = -4.7 to 8.81). Roundness index averaged 45.57% and ranges 36.00% and 55.50%. The integration of the results of granulometric parameters and between pebble morphometric indices using different bivariate plots indicate fluvial to shallow marine environment of deposition for the Benin Formation.