Palynology: A Useful Tool for Biostratigraphic and Palaeoenvironmental Reconstruction of t

Abstract

This paper presents a biostratigraphic and palaeoenvironmental interpretation from the lithostratigraphic, gamma-ray log and palynological data of Uk-4 Well from the late Miocene interval of the offshore western Niger Delta Basin. Three lithologies that comprised sandstones, argillaceous sandstones and sandy-mudstones were recognised from both lithostratigraphic and well log analyses. Sandstones and argillaceous sandstones could be regarded as reservoir rocks, sandy-mudstones, on the other hand, could be considered as seal and source rocks. Five transgressive and three regressive depositional sequences, and three sequence stratigraphic surfaces comprising two sequence boundaries and one maximum flooding surface were recognized from the lithostratigraphical analysis. Sixty-nine palynomorph species belonging to 22 genera that is dominated by angiosperm assemblages were recovered from palynological analysis. The palynomorph assemblages were grouped into seven ecological groups, which comprised fresh water, savanna, brackish water swamp, mangrove, lowland rainforest, palmae and beach in order of their dominancy. Five informal palynological assemblage zones were delineated from the palynological assemblage analysis. Hence, the near shore/coastal deltaic and marginal marine paleoenvironments were inferred for the penetrated strata of Uk-4 Well. The recovered palynomorphs showed a relationship with the Echitricolporites spinosus Pan-tropical zone, which correlate with P800 palynological zone (P830, P840 and P850 sub-zones), J2-J3, and M4, M3 and M2 floral zones, and hence, Uk-4 Well was dated late Miocene. Deep water marine, prograding delta, basin floor fans, channel fill and tidal channels environments of deposition that are considered as mud and sand facies, are inferred from five delineated gamma-ray log shaped sequences. This investigation may be a functional means for forecasting facies associations and basin geometries in related Miocene hydrocarbon systems.

Publication Info:

Author: Olayiwola, M.A. , Durugbo, E.U. and Fajemila, O.T.

Volume: 58

Issue: September

Published By: Journal of Mining and Geology Vol. 58(2) 2022. pp. 11 - 28, 2022-09-21