Late Miocene to Early Pliocene Palynostratigraphy and Palaeoenvironments of ANE-1 Well, Eastern Niger Delta, Nigeria

Abstract

Fifty ditch cutting samples composited at 60ft intervals between 6990ft and 9930ft in the Ane-1 well, Niger Delta were processed for sedimentological and palynological analyses. The sedimentological study showed that the analysed section belongs to the paralic Agbada Formation. The section is subdivided into three lithofacies subunits based on their shale/sand ratios: Lower Biafra (9,930-8,035ft), Middle Biafra (8,035-7,115ft), and Upper Biafra (7,115-6990ft). A total of 632 palynomorphs were identified from which some were selected for microphotography. The diagnostic palynomorphs recovered permitted the zonation and dating of the analysed section. A Late Miocene to Early Pliocene age was assigned to the studied section with Miocene/Pliocene boundary placed at 8150ft and marked by First Appearance Datum (FAD) of Nymphaeapollis clarus and increase in Monoporites annulatus. The section belongs to the Echitricolporites spinosus Zone. Palaeoenvironmental interpretation of strata penetrated by Ane-1 well was conducted by combining association of environmentally restricted marker species; percentage of Zonocostites ramonaein the total palynomorphs sum; nature of organic matter in the sediment; and lithological characters of the strata. The result shows that the overall environment ranges from coastal to marginal marine. Foram test linings was used to subdivide the macro environments into coastal deltaic, coastal deltaic inner neritic, and inner neritic.