Palynostratigraphy of Late Cretaceous subsurface sediment of southern Bornu Basin, Nigeria: Implications for depositional environments and palaeoclimatic predictions.

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Sedimentary records are helpful in tracking ancient environments and climates. By analysing Late Cretaceous subsurface sediment from the Gaibu-1 Well in the southern Bornu Basin, Nigeria, predominantly arenaceous lithologies were identified, and five stratigraphic sub-divisions were recognised: Bima, Yolde, Gongila, Fika (Upper, Middle, and Lower members), and Gombe Formations. Palynozonation facilitated the identification of four assemblage zones (A1 – A4): A (1) Triorites africaensis, A (2) Cretacaeiporites scabratus/Odontochitina costata, A (3) Droseridites senonicus, and A (4) Syncolporites/Milfordia spp. These findings suggest that the subsurface Cenomanian – Maastrichtian (younger) successions were deposited in the inner continental shelf (4600–3420 m), middle continental shelf (3420-2300 m), and distal middle continental shelf (2300-1500 m) settings. This Late Cretaceous succession is characterised by monocolpate pollens resembling modern Cenomanian palms, Nypa vegetation in wet lowland habitats, and conifer vegetation in relatively dry hinterlands during the Turonian-Maastrichtian, all under a tropical to subtropical climate systems. The data advocate that the Late Cretaceous era was characterised by prevalent tropical to subtropical climates featuring warm and humid conditions. This aligns seamlessly with the recognised Cretaceous Palmae Province of Africa–Southern America. This research demonstrates the reliability of integrated sedimentological and palynozonation datasets for refining the current understanding of ancient depositional environments and climate.