Palaeocurrent and Petrographic Evaluations of Sandstones in the Cretaceous Gulani Formation of the Eastern Gongola Basin, North-east Nigeria: Its Implication for Provenance Studies

The Turonian Gulani Formation of north-eastern Nigeria is characterized by a dominant subfacies represented by tabular cross-bedded, medium to very coarse-grained quartz arenites and granulestones with individual sets frequently several metres thick. The palaeocurrent indicates an easterly source area with the main focus of sediment influx located around latitude 10o46' north, the point of origin, on a gross scale, of a deltaic body. Within this body, small Gilbert-type delta lobes are thought to have formed in association with the major delta distributary channels. Petrographically the cross-bedded sandstone subfacies is medium to very coarse-grained, poorly to well sorted, sub-angular to well rounded quartz arenite, consisting of majorly monocrystalline quartz and rare polycrystalline quartz with a kaolinitic matrix. This subfacies is characterized by the extreme rarity or absence of feldspar, low diversity heavy mineral suites and the presence of sedimentary rock fragments, suggesting a sedimentary source area, probably in large part comprising Late Cenomanian to Early Turonian littoral sands deposited during a major preceding transgression. Keywords: Turonian; Gulani Formation; north-east Nigeria, tabular cross-bedded sandstone subfacies; paleocurrent directions; Late Cenomanian to Early Turonian reworked littoral sands