Lithofacies, Palynology and Facies Association: Keys to Paleogeographical Interpretation of the Enugu and the Mamu Formations of Southeastern Nigeria

Abstract

The lithofacies, palynological assemblages and facies association have been employed in the interpretation of depositional setting, paleogeography and age of the Enugu and the Mamu Formations of the Anambra Basin, southeastern Nigeria. Palynological analysis yielded index sporomorphs and marine dinoflagellates typical of the Late Campanian to Early Maastrichtian for the Enugu Formation and Early- Mid Maastrichtian for the Mamu Formation. The coarsening upwards characteristics of the lithofacies and the general decrease to the absence of marine dinoflagellates coupled with an increase in the abundance of sporomorphs from the Enugu Formation into the Mamu Formation suggest shallowing of the sea.  There is also a gradation from transgressive to regressive facies association. Late Campanian marine transgression deposited the basal part of the Enugu Formation. Seaward advancement of the shoreline commenced during the Early Maastrichtian in the Enugu Formation and continued into the Mid Maastrichtian in the Mamu Formation.

Key words: Paleogeography, Sporomorph, Lithofacies, Dinoflagellate, Transgression, Regression