Continental Intercalaire Gr

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

[Fig. 1. Stratigraphic successions in the Nigerian sector of the lullummeden Basin (Sokoto Basin)]

Gundumi Fm is the lateral equivalent of the Illo Fm north northeast of its outcrop and it consists of a basal conglomerate that grades upwards into coarse and pebbly sandstone, mudstone, clayey sandstone, claystone and sandstone, the top of which is intensely lateritized. The Gundumi Fm lies unconformably on the basement and consists of basal conglomerates, and gravels with sand and variegated clays increasing upwards; the maximum thickness is about 350 m. The contact of the Gundumi Fm with the basement is conglomeratic. At Kona Rolga, on the Sokoto-Gusau road, a good exposure of the basal conglomerates occurs at about 11 km north of Talata Mafara where the basement outcrops. These conglomerates outcrop for hundreds of square kilometres, with large, well-rounded pebbles in a massive clayey feldspathic and ferruginous matrix. The pebble conglomerates occur also abundantly around Tureta.

Illo Fm includes interbedded clays and grits, with an intermediate pisolitic and nodular clay member, and attains over 240 m. The deposits are continental, fluviatile to fluvio-lacustrine in origin.