Petrographic and Sediment Logical Studies of Bima Sandstone Formation out Croped at Lokoro area, Yola Arm of the Benue Trough, Northeastern Nigeria

Abstract

Petrographic and Sedimentological Studies of the Bima Formation which outcroped at Lokoro area of Guyuk was conducted. This was achieved after mapping the area on a scale of 1:25,000. Analyses on the textures, lithologies and the environment of deposition of the Bima sandstone is presented.The Bima Sandstone of Lokoro area of Guyuk are mostly medium to coarse grained, texturally and mineralogically matured quartz arenites. The formation shows lateral variation in thickness and consists of arkosic, clayed, medium to very coarse cross bedded sandstone. In the thin section the grains are prodominantly quartz with many of the quartz floating in the cement while other grains exhibits point contacts. Some dark colour mineral grains, greyish and little brownish mineral grains were visible under the petrographic microscope. The petrographic studies also shows that sample is mainly silica in the form of quartz and iron oxides are predominantly the cementiing materials for the Bima sandstone as seen in Figure #2, #3, #4 and #5.The grain sizes range from 1.36 – 1.83mm indicating a medium – coarse grained sandstone that is poorly sorted.This poorly sorted attribute noted is a disqualification of the Sandstone from being an ideal potential reservoir in the basin. The quartz present is sub-angular to subrounded with iron oxide induced reddish brown colouration.