Pebble Morphometric Studies of Part of Bida Formation, Northern Bida Basin, North Central Nigeria

Abstract

The Bida formation exposed in Doko locality, Bida town appeared Massive, poorly sorted with localized sedimentary structures. The formation shows three lithofacies: mf, ssf and sf respectively. The formation grades into more matured upward, the pebbles are found within the sf unit as lenses and as scattered pebbles. Vernier caliper was used to measure the Longest, intermediate and shortest axes that are mutually perpendicular for each pebble. These values were used to compute different morphometric parameters as a single variable including MPSI, OPI, FR, ER, R and CF. These parameters were also used as dependent variables in bivariate plots to characterize the depositional process. The average values of MPSI, OPI, FR, ER, and CF are: 0.64, 3.01,0.41, 0.63, 44.5 and 40.73 respectively. The ternary plot of the ratios of the three-axis showed that most samples fall within Bladed(B) field while some other few on Elongate(E) Field, the plot of MPSI versus OPI, FI versus MPSI and R versus ER. Both independent and dependent parameters showed that the Bida formation was deposited by both river and beach processes. Its therefore deduced that the fluvial deposits were later modified by marine activities, possibly during the transgression period.