Provenance and palaeogeographic history of the Turonian Makurdi sandstones in the Benue Trough of Nigeria
Abstract The sandstones of the Makurdi Formation of Nigeria (Turonian) consist mainly of texturally immature, pebbly arkosic wacke with minor arkosic arenite. The feldspathic composition of the sandstones, the dominance of monocrystalline nonundulose quartz grains, and frequent occurrence of vein quartz pebbles, with occasionally large microline clasts, suggest derivation from granitic basement complexes associated with little or no metamorphic rocks. Ternary plots of framework modes as well as composition and textural characteristics of the heavy minerals indicate derivation of detritus from uplifted dispersal centres of a continental block provenance region of plutonic affinities. The crystalline basement terrains flanking the Benue trough, both within and outside Nigeria, satisfy such an uplifted source model. Deposition of the clastics took place mainly during the occasional reversals of the predominantly transgressive sea movements in the Benue trough during the Late Cretaceous.