Tossiegou Fm

The unit is exposed in the Gambaga- Nakpanduri areas, northeastern parts of the Basin. The Tossiegou Fm of Affaton et al. (1980) is the equivalent of the Yabraso Fm of the Kwahu areas (Carney et al. 2010).

Synonym: Tossiegou Sandstone Fm, Basal Sandstone (Annan-Yorke, 1971; Blay, 1983).

References: Edmonds, 1956; Annan-Yorke, 1971; Affaton et al., 1980; Blay, 1983; Carney et al. 2010; Anani et al. 2017

[Fig. 1. Geological map of the Volta Basin and surroundings, after Sougy (1970) and Affaton et al. (1980).]

[Fig. 2. Schematic lithostratigraphic sections showing principal lithologies and inferred correlations between Kwahu and Bombouaka group units across the Volta Basin.]

[Table 1. Published stratigraphic data available for Voltaian deposits]

[Table 2. Proposed lithostratigraphic scheme (left-hand column) compared with previous nomenclature.]

[Fig. 3. Synthetic lithologic section of the Volta Basin sedimentary infilling]

In the Gambaga location, Edmonds (1956) demonstrated that the lower part of the formation, which overlies Paleoproterozoic basement, consists of argillaceous strata occurrence in its francophone extension (Affaton et al. 1980), characterized by symmetric and asymmetric ripple marks in the Nakpanduri areas (Anani et al. 2017).These grade up into both feldspathic and ‘clean’ quartzitic sandstones, which are commonly ripple-marked and include coarse-grained sandstones and ‘grits’.

The Tossiegou Fm is the equivalent of the Yabraso Fm of the Kwahu areas (Carney et al. 2010).

Deposition in a shallow marine or deltaic environment.