Miospore Biozonation and age characterization of Upper Miocene - Pliocene sediments in well X, deep offshore Niger delta.

Abstract

Miospore biozonation carried out on ditch cutting rock samples has been used to delineate the Upper Miocene/Pliocene sediments in well X, deep offshore, Niger delta. The rock succession is characterized by the alternation of sand and shale of variable thicknesses with lateral gradation in grain size. The base of the studied interval is made of Black shales intercalating with medium to coarse grained, sub rounded to rounded sandstone and siltstone at intervals representing the paralic Agbada formation while the top is made of Sub angular sub rounded quartz pebble conglomerate, pebbly sandstone, medium coarse grained, subrounded to well-rounded sandstone, intercalating with very thin lenses of grey shales typically of the coastal plain sand of the Benin Formation. The palynological characterization of the well yielded a well preserved and diverse biostratigraphic important Miospores among which sixty-one miospores (fifty-one pollen and ten spores) were identified and used to erect ten miospore zones. The biozonation is premised on the recognition of the first and last downhole occurrences of these Palynological events. The zones are defined from the base to top as follows: Magnastiatites howardi, Inerperturopollenites sp, Caryapollenites veripites, Striatricolpites catatumbus, Verrutricolporites rotundiporis, Echitriporites spinosus, Canthimidites sp, Pordocarpus milanjanus and Verrutriculporites rotundiporis. Correlation with the existing pantropical zones yielded Upper Miocene to Pliocene age. Results from textural and lithological analysis show that the rock succession penetrated the Agbada and Benin Formations.