Awgu Fm

The type locality is in Awgu Town in Enugu State The major outcrop of the coal-bearing Awgu Fm is at the bank of River Dep in Shankodi, 7 km to the west of the village of Jangwa. Along the bank of this river, the coal seams can be traced laterally for about 500 m. The borehole cores of the Steel Raw Materials Exploration Agency (formerly National Steel Council) stock-piled at the Obi camp contain coal seams and coal bands at various depths within the Awgu Fm.

Synonym: Awgu-Neaboh Shales (Whiteman, 1982). Contains Makurdi Sandstone Fm in Makurdi area. Awgu – Ndeaboh Shales (Simpson, 1955; Geological Survey of Nigeria and Shell-D’Arcy in International Stratigraphical Lexicon, 1956; Reyment, 1965), Cross River-Benue Shales, Awgu Sandstones and Shales; Awgu Gr (due to subdivisons in South Benue Trough)

References: Reyment, 1965; Adeleye, 1975; Kogbe, 1976; Dessauvagie, 1975; Petters, 1978; Offodile, 1980; Whiteman, 1982; Benkhelil, 1989; Okosun, 1992; Guiraud, 1993; Akande et al., 1998; Zaborski et al., 1998; Jauro et al., 2007; Obaje, 2009; Nwajide, 2013

The formation is made up of bluish-grey to dark-black carbonaceous shales, calcareous shales, shaly limestones, limestones, sandstones, siltstones, and coal seams. The shale is fissile, bluish-grey, pyritic, calcareous, micaceous, and occasionally gypsiferous. The sandstones are pale yellow, fine to medium-grained, and calcareous. The limestones are marly and shelly, and add up to several meters in thickness (Nwajide, 2013). In the Makurdi area, the Makurdi Sandstone Fm interfingers within the Awgu Fm. Thickness ranges between 300 to 600 meters; but the overall thickness is also report to be 900m (Simpson, 1954; Reynment, 1965) and can be up to 1,100m from well data (Agagu et al., 1985).

Arenaceous foraminifera, Bivalves, Gastropods, Ostracods, Palynomorphs. Foraminifera (Ammoaculites sp., Haplophragmoides sp., Gavelinella sp., Heterohelix globulosa, Heterohelix reussi, Hedbergella amabilis), Ostracods (Buntonia vanmorkhoveni), Ammonites (Texanites sp.)

Late Cretaceous. Indicated as mid-Turonian through early Santonian on the schematic diagram for Benue Trough; followed by a late Santonian episode of folding. In the Makurdi area, the Makurdi Sandstone Fm that is shown as spanning the Coniacian interfingers with the Awgu Fm.

The deposition of the Awgu Fm marks the end of marine sedimentation in this part of the Benue Trough. Deltaic-Marine environment depositional. sediments were deposited in a shallow-marine shelf environment and this setting is characterized by relatively calm, open marine conditions with occasional influences from deltaic and near-shore processes. Some levels in South Benue Trough indicate an anoxic bottom condition due to the paucity of benthic foraminifers (Nwajide, 2012)