Integrated Palynostratigraphy, Sedimentology and Petrography of the Maastrichtian Gombe and Paleocene Kerri-Kerri Formations, Gongola Basin, Northeastern Nigeria

The Gongola Basin (Upper Benue Trough, Nigeria) preserves a critical but understudied record of non-marine to marginal-marine sedimentation across the Cretaceous–Paleocene boundary. This study integrates high-resolution grain-size analysis (median diameter D50, Trask sorting coefficient (So), inclusive graphic standard deviation δ1, and mud content), calcimetry, and palynology from 27 shallow drill-hole samples across nine locations. Four lithological classes are defined: sandstones (>80% sand), muddy sandstones (50–80%), sandy mudstones (20–49%), and mudstones (<20%). The textural parameters are highly variable: D50 = 0.042–1.560 mm, So = 1.31–3.82, δ1 = 0.021–2.180, and mud = 1.19–90.72 wt.%. Calcite contents are generally low (0.03–8.12 wt.%), with one outlier (C3: 8–14 m) at 24.77 wt.%. No foraminifera or nannoplankton are present, but palynomorphs are abundant to sparse. Diagnostic palynomorph assemblages assign a Maastrichtian age to locations C17, C18, C20, and C26 based on the presence of Proteacidites sigalii, Retidiporites magdalenensis, Cingulatisporites ornatus, Constructipollenites ineffectus, and Scabratriporites simpliformis. A Paleocene age is assigned to C3, C8A, and C9–9B based on the identification of Proxapertites cursus, Monoporites annulatus, Heterocolpites laevigatus, Retibrevitricolpites triangulatus, and Retistephanocolpites williamsi. The C13 interval is age-non-diagnostic. Texturally, all samples except five C13 sandstones are immature (mud > 5%). Those five are submature to mature (mud < 5%, D50 up to 1.56 mm, moderate to very good sorting), indicating higher-energy fluvial reworking. The co-occurrence of freshwater swamp, mangrove swamp, and hinterland palynomorphs, plus sparse marine dinoflagellate cysts and microforaminiferal linings, defines a fluviatile–lagoonal–tidal flat complex. We propose that the Gongola Basin represented a low-accommodation coastal plain where mixed-energy processes operated across a narrow transition from continental to paralic settings. This integrated dataset provides a regional reference framework for comparing Maastrichtian and Paleocene successions in the Gongola Basin and demonstrates the value of combining textural maturity indices with palynofacies in data-sparse rift basins.