The Sedimentology Of Gambaga Massifs Of The Northeastern Voltaian, Ghana.

Abstract

The sedimentary facies of the investigated area of the northeastern Voltaian, with respect to the

sedimentary structures, composition as well as the depositional environments, can be classified

into six (6) facies. The sediments are deposited dominantly in a shallow marine environments with

records of shoreface/foreshore, Aeolian and tidal environments. The sediments were deposited in

the various environments by both low and high energy media. The area shows a shallowing and

thickening upward facies sequence. The paleocurrents of the sediments show a dominant

southwestern source with minor contribution of sediments from the south and south east eastern

parts.

The sediments are composed of quartz, dominantly monocrystalline with undulatory extinction

(strain) with minor polycrystalline, potassium feldspars, plagioclase feldspars, micas, sericites as

the matrix, zircons and some accessory minerals from the petrographic study of the collected

samples. The sediments studied are moderately – highly weathered in a relatively gentle – flat

terrain. The composition of the clastic sediments shows high temperature regimes, dry/arid –

moderate humid climatic conditions in a most probable poor rainfall environments. The sediments

of the studied area from petrography, are the weathering products of granitic rocks, granitic

gneisses and sedimentary rocks. The source area of the investigated area can be most likely traced

to the adjacent Birimian Supergroup. Geochemically, the studied samples of the Gambaga –

Nakpanduri area can be grouped into sublitharenite, subarkose and quartz arenites using log

(Fe2O3/K2O) versus log (SiO2/Al2O3) bivariate plot. The weathering indices, thus, Chemical Index

of Alteration (CIA), Chemical Index of Weathering (CIW), Thorium – Uranium ratio (Th/U) and

Index of Compositional Variability (ICV) all supports a moderate – highly weathered and matured

(ICV