V. Haruna*, C. J. Dio, Y. D. Mamman and Y. B. Valdon
Petrographic analysis of Bima sandstone of the Upper Benue Trough was attempted using field observations and representative samples from two widely separated areas. Petrographic and textural analysis of sandstone in both areas shows that the sandstone contains about 90% quartz and only about 5% orthoclase with iron oxide, silica and clay matrix as cementing materials. The grains of framework detritus range in size from coarse- to fine-grained and mostly sub-rounded and moderately sorted with no angular fragments. Interpretation of the results revealed that the sandstone is mostly quartz-arenites and arkose of mostly plutonic and metamorphic origins sourced from the crystalline basement of Adamawa, Cameroon, Mandara and Hawal Massifs, which border the trough as the source areas. Bima sandstone was formed during tectonic quiescence and in a humid tropical climate in the Mid-Cretaceous times. The deposition of the Bima sandstone was construed to have marine shoaling influence in a fluvio-deltaic environment.
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