| Summary: | This study presents the results of a comprehensive qualitative and quantitative palynological analysis
of four shallow boreholes (Epe-1, Olokonla-1, Ikoyi-1 and Badore-1) in the lower Eocene–upper Oligocene periods of
the Dahomey Basin, southwestern Nigeria. The lithostratigraphic analysis revealed three lithologies (sandy-shales,
shaly-sands and sandstones). Two most important palynological zones, the Verrucatosporites usmensis , as well as
the Magnastriatites howardi Pan-tropical zones, are delineated. First Appearance Datum (FAD) of Achomosphaera
alcicornu marked the late Eocene–early Oligocene boundaries (E/O) within the four boreholes, while FAD of Adnatosphaeridium
multispinosum defined the late Eocene–early Oligocene boundary (E/O) in Ikoy-1. Two informal
palynological assemblage zones were revealed in the four boreholes. Common occurrences of palms, mangrove,
fresh water and brackish water pollen, and pteridophyte spores with spots records of marine elements and algae
species during marine invasion suggested fluctuation from fluvio-deltaic/nearshore to marginal marine paleoenvironments.
Graphic correlation discloses that for every meter of sedimentary rock accretion within Epe-1, equally
amounted to merely 0.31 m, 0.56 m, as well as 0.47 m of sediments, which were put down in Olokonla-1, Ikoyi-1,
as well as Badore-1, respectively. These comparative rates of sedimentary rock accretion show with the purpose of
either there is fewer attrition occurrence and/or extra accommodation gap within Epe-1 than Olokonla-1, Ikoyi-1,
as well as Badore-1. The assessment of the slopes, intercept and correlation equations through graphic correlation
procedures enable the identification of four biostratigraphic events in Epe-1, Olokonla-1, Ikoyi-1, as well as
Badore-1. The findings in this investigation are necessary for depositional succession and paleoenvironmental
understandings, as well as basin investigation, and above all, to show a relationship of broadly separated boreholes.
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