Abstract:
Lithofacies and palynological studies of Enugu and Mamu Formations were carried out at Agu-Abor area
of Enugu, Southeastern Nigeria, with the aim to identify and document the fossil assemblages in order to
establish the age and paleoenvironment of deposition. The lithologic units identified consist of shales,
siltstones and sandstones. The coarsening upward sequence of the lithofacies of Mamu Formation is an
indication of decrease in sea level, and the intercalation of siltstone/sandstone and shale in the lithofacies
of Enugu Shale suggest a shallow-marine environment with tidal influence. Sedimentary structures
observed in the formations include wave ripple lamination, parallel lamination, cross lamination and
widespread burrows by trace fossils such as Planoliths and Skolithos. The palynological analysis carried
out on forty (40) samples across Enugu and Mamu Formations yielded forty seven (47) spores/pollens and
marine dinoflagelates that are of Early Campanian to Mid Maastrichtian for Enugu Shale and Middle
Maastrichtian for Mamu Formation. The main diagnostic species of spores and pollen that show high
abundance recovered include; Monocolpites marginatus, Longapertites, Retidiporites magdalenensis,
Buttinea andrevii, Zlivisporites blanensis, Operculodium centrocarpum, Cingulatisporites ornatus
Spinozonocolpites baculatus, Laevigatosporites sp, Leiotriletes adriennis, Echitriporites trianguliformis,
Longapertites marginatus and Cyathidites minor. Among the main diagnostic dinoflagellates are
Cleistosphaeridium sp, Diphes colligerum, lingulodium machaerophorum, Oligosphaeridium and
Microforaminiferal wall lining. The relatively high abundance and diversity of spores and pollen in the
formations is indicative of a tidally influenced shallow marine to coastal swamp environment. The
dinoflagellate distribution marked instances of fully marine conditions,an assertion which is supported by
PMI value above the threshold 100. The inferred ecozones are mangrove vegetation and back mangrove
vegetation based on the abundance of mangrove elements such as spinizonocolpites and longapertites group
for the two Formations.
