Agbaja Ironstone Fm

This formation is located within the Agbaja Plateau

Reference section: Reyment,1965; Adeleye,1975; Dessauvagie, 1975; Kogbe, 1976; 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

[Fig. 1 Stratigraphic successions in the Mid-Niger Basin (also known as Bida or Nupe Basin)]

It consists of sandstones and claystones interbedded with oolitic, concretionary and massive ironstone beds in this region. The sandstones and claystones are interpreted as abandoned channel sands and overbank deposits influenced by marine reworking to form the massive concretionary and oolitic ironstones observed (Ladipo et al., 1994).This oolitic ironstone formation is estimated to be about 7-15m thick and associated with laterite which is up to 11m thick in places. It forma the youngest and topmost unit of the Southern Bida Basin and consists interbeds of clay and sandstones, with plant remains as well as shell beds with oysters and gastropods (Nwajide, 2013). Four ironstones lithofacies – ooidal pack-ironstone, pisoidal pack-ironstone, detrital mud-ironstone, and breccia mud-ironstone - were recognized by Abimbola(1997) and Abimbolaet al. (1999).

Gastropods, Plant remains, Oysters

Late Cretaceous (late Maastrichtian; with assumed gap at K/T boundary)

marginal marine to deltaic depositional environment. The presence of ironstones suggests periodic episodes of iron precipitation in a shallow, restricted marine setting, likely influenced by fluctuating sea levels and climate conditions. Wave action and persistent fluvial input (Nwajide, 2013)