Onuigbo E. N., Okoro A. U., Etu-Efeotor J. O., Akpunonu E. O. and Okeke H. C.
Paleoecology of the Enugu and the Mamu Formations was studied based on microfloral and ichnofossil assemblages preserved in the sedimentary units of the formations. The non marine microfloral is dominated by angiosperm (mostly monocolpate pollen) and pteridophytes (trilete spores). Chorate cyst gonyaulacoid dinoflagellates constitute 86.31% of the marine palynomorphs. The basal shale unit of the Enugu Formation documents very few Senegalinium bicavatum and sparse burrows of Thalassinoides isp. The middle to upper (heterolithic) units together with the heterolithic units in the Mamu Formation document Skolithos, Planolites and Teichichnus. A paleoecological model developed for the Late Campanian- Mid Maastrichtian ecosystems was interpreted as follows; mangrove vegetation fringed by the pteridophytic plants surrounds the ancient sea. The gonyaulacoids constitute the autotrophs while the peridinoids are the heterotrophs. Marine organisms that constitute the Skolithos, Teichichnus and Planolites are carnivores, deposit and suspension feeders. The greater concentration of these dinoflagellates and the ichnofossils within the neritic zone suggests more productivity. Few Senegalinium and sparse burrows recorded by only the basal shale of the Enugu Formation (open marine) are attributed to unfavorable condition due to anoxic bottom condition, salinity fluctuation and poor circulation of the ancient Sea.
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