Gombe Fm

This formation is situated in the Kware River at the southern outskirts of Gombe Town where about 310m of sandstones, with mudcracks and ironstones with a disconformity within a 30m sandstone midway up the section. The Gombe Sandstone is along the bank of Pantami River in town. Good exposures are also encountered in many parts of Gombe town and Birin Fulani village.

Synonym: Gombe Sandstone

References: Carter et al., 1963; Dike, 1993; Whiteman, 1982; Zaborski et al., 1997; Obaje et al., 1999;Ojo and Akande, 2004; Ojo and Akande, 2004; Ayok and Zaborski, 2005;

[Fig 1. Stratigraphic successions in the Benue Trough and the Nigerian sector of the Chad Basin]

Siltstones and flaggy sandstones form the greater part of the Gombe Sandstone, the rocks are soft and light grey in color when fresh, but on exposure give rise to a dark red, flaggy debris (Carter et al., 1963). Cross-bedding, planar bedding, and ripple marks are common, indicating deposition in fluvial channels and deltaic environment. Under the Chad Basin, it generally is made of intercalations of siltstones, shales and ironstones but without coal seam interactions as in the Upper Benue Trough (Obaje et al., 1999). Thickness: range from 150 to 300 meters.

The Gombe Sandstone is lithologically similar to the Bima Fm (Bima Sandstone Fm), attesting to the reestablishment of the Albian paleoenvironmental condition. The Gombe Sandstone Fm, however, contains coal, lignite, and coaly shale intercalations which in some places are very thick. medium to coarse-grained light grey to yellowish-brown, composed primarily of quartz grains with minor amounts of feldspar and lithic fragments.