Palynological analysis of the Maastrichtian Patti Formation in Gehuku and Ahoko area, southern Bida Basin, Nigeria: implications for age and paleoenvironments

Detailed palynological examination has been carried out on outcrop shale and claystone samples recovered from Ahoko and Gehuku sections in the Patti Formation, southern Bida Basin. The age and paleoenvironments of deposition of this samples were attempted. A total of 18 samples of shale and claystone were prepared and examined. Palynological results of the examined shale samples show high dominance of terrigenous microflora (spores and pollen), over marine dinoflagellate cysts, mostly species with proximate cyst affinity. A Maastrichtian age was assigned to the formation based on marker palynomorphs taxa: Longapertites marginatus, L. vaneedenburgi, Spinizonocolpites baculatus, Retidiporites magdalensis, Constructipollenitesin effectus, Cingulatisporites ornatus, Distaverrusporites simplex, Echitriporites trianguliformis, Monocolpites marginatus and Foveotriletes margaritae. This assemblage is typical of Maastrichtian species belonging to the palmae provinces of tropical Africa and South American regions. The age was further confirmed by co-occurrence of a well-known age-diagnostic Maastrichtian endemic dinoflagellate cysts species such as Dinogymnium acuminatum. Palynomorphs of environmental value include the fresh water ferns such as Laevigatosporites spp. and Leiotriletes spp., and pollen of palm: Spinizonocolpites baculatus/echinatus, Longapertites marginatus, Mauritidites crassibaculatus and Moncolpites marginatus, which inhabit similar brackish water as the mangrove. The presence of these terrigeneous species alongside the occurrence of the peridinioids dinoflagellate cysts species association such as Dinogymnium spp., Glaphyrocysta spp, Andalusiella sp. and Paleocystodinium spp., indicate deposition in different sedimentary environments, oscillating from marginal marine (brackish water) estuarine in the lower deltaic plain, to non-marine (fresh water mangrove swamp) in the Upper deltaic plain, within the tropical rainforest. The recovered miospores indicated a periodic wet and dry prevailing paleoclimatic conditions. The present findings have contributed to broader paleoclimate studies, helping to establish how climate has influenced sedimentation and biotic communities in the region over time. This also provided context for current climate change discussions by offering a long-term perspective on environmental shifts.