Impact of Magmatic Activity on Late Cretaceous Foraminifera Assemblages of the Middle Benue Trough, Nigeria

Core samples obtained from Makurdi-1 borehole located within the Middle Benue Trough, Nigeria, were analysed for foraminifera and lithological properties. This study aimed to use the lithological characteristics and foraminifera assemblages from the borehole as proxies to investigate the biotic effects of magmatic activity in the Middle Benue Trough during the Late Cretaceous. The samples yielded low diversity, oligospecific foraminiferal assemblages comprising dominantly Late Cretaceous Heterohelicids and Ammobaculites species, which include Heterohelix reussi, Heterohelix pulchra, Heterohelix globulosa, Ammobaculites coprolithiformis, Ammobaculites jessensis, Ammobaculites bauchensis and Ammotium nkalagum. Inter-bands of volcanic syenite sills were identified within a dominantly dark shale borehole section, indicating episodes of magmatism in the Benue Trough. The exclusive low-oxygentolerant Heterohelicid planktic populations and Ammobaculites-dominated benthic foraminiferal communities indicate significantly perturbed marine-pelagic and benthic ecosystems occasioned by episodes of magmatic eruption.