Palaeontological Study of Foraminifera in Cretaceous Sediments of Borno State

Foraminifera preserved within Cretaceous sedimentary sequences in Borno State, North East Nigeria, provide invaluable biostratigraphic markers and palaeoenvironmental proxies that can refine stratigraphic correlation and reconstruct ancient depositional conditions in the Chad Basin. This study investigates the assemblage composition, preservation state, and biostratigraphic significance of foraminifera recovered from outcrop samples collected in the Gongola Sub-basin and Chad Basin portions of Borno State. Rock samples were disaggregated using warm water soaking and washing over fine mesh sieves, with the greater than 63-micrometre fraction picked for foraminiferal study under a binocular microscope. Identified species were classified following standard taxonomic references, and assemblage diversity indices including species richness and Shannon diversity were computed. Biozone assignments were made by correlating identified index species against established Cretaceous biozonation schemes for West Africa. Palaeoenvironmental interpretation was based on benthic foraminiferal morphogroups and planktonic-to-benthic ratios, used to estimate palaeobathymetry and oxygenation conditions during deposition. The study evaluates whether assemblages are consistent with a shallow epicontinental marine setting or transitional lacustrine influence as proposed in some regional models. Findings contribute to the biostratigraphic database for the Chad Basin and provide undergraduate students with fundamental micropalaeontological skills. Keywords: foraminifera, biostratigraphy, Cretaceous, Borno State, Chad Basin.