The Abakaliki pyroclastics – Eastern Nigeria: new age and tectonic implications

Abstract

Summary Basic to intermediate pyroclastic rocks of pre-Albian age are overlain by the Abakaliki shale of Asu River Group in Eastern Nigeria. The shale has been assigned Albian age on the basis of abundant (middle Albian?) ammonites found in it. It was folded (together with the pyroclastics) about a NE–SW trending anticlinal axis during the Santonian time. This new evidence of an early Cretaceous volcanism supports a pre-Albian rifting of the African shield prior to the opening of the Southern Atlantic. The latter event took place (probably in stages) during Albian time ( i.e. less than 110 Ma ago), with a widespread marine transgression in West Africa and South America.