Ola-Buraimo AO and Akaegbobi IM
Ditch cutting samples of interval 24-354m from Umuna -1 well were analyzed for palynomorphs. The interval yielded diverse abundance of dinoflagellates and diagnostic miospores. The marker dinocysts present are Selenopemphix nephroides, Multispinula quanta, Tuberculodinium vancampoae, Polysphaeridium zoharyi, Impagidinium spp, Oligosphaeridium sp, and Thalassiphora sp which are mainly of Late Miocene to Pliocene age. Presence of diagnostic pollen such as Nymphae lotus, Elaeis guineensis, Cyperacaepollis sp, Podocarpus millanjianus, Retistephanocolpites gracilis, Arecipites sp and Echitricolporites spinosus serve as control for age dating of the sediments. The paleoenviroment of deposition varies from inner neritic, characterized by Selenopemphix nephroides; inner neritic to outer neritic, defined by Operculodinium spp, Polysphaeridium zoharyi, Tuberculodinium vancampoae; while the outer to oceanic setting is marked by Impagidinium sp, and Operculodinium centrocarpum. Lithologic inference is mainly shale coupled with abundance of dinoflagellate cysts, microforaminiferal wall linings, and the predominant marine environments of deposition substantiate the fact that the formation is Ogwashi-Asaba not Benin Formation. This segment of the formation is suggested to be laterally equivalent both lithologically and age to upper part of the Agbada Formation in the adjacent Niger Delta. Evidence of reworked dinocysts and miospores is apparent in the analyzed samples which may suggest that the sediments are admixture of fresh and reworked materials of preexisting older rock probably Oligocene in age. A hiatus is thought to exist between the Late Miocene and the overlying younger Pliocene sediments.
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