Biostratigraphy and Paleoenvironmental Analysis of Strata Penetrated by Igbomoturu-I-Well, Niger Delta.

Oboh, Francisca Emiede (1986)


Palynological investigations were carried out on the subsurface strata of the Igbomotoru-l-Well in the Niger Delta. A lithostratigraphical interpretation of the Well resulted in the delineation of four informal nits referred to as P, P, C and I these units show lithologic characters of the Benin and Agbada Formations. The studied interval (1,123-3,583 metres) was assigned an Upper Miocene age on the basis of its palynological assemblage. These diagnostic forms were Crassoretitriletes anraadshooveni, Peregrinipollis nigericus, Zonocostites ramonaee and Multiareolites formosus. Of the 207 recognised palynomorph species representing 45 spore and 162 pollen species, only 11 were selected for biostratigraphical interpretation. This was as a result of the poor and irregular distribution of the species, many of which were usually corroded. The selected forms included the earlier named species and Pachydermite diederixi, Polypodiaceicsporites sp., Magnastritites howardi, Clavamcnocolpites sp. and Fetitricolpites sp.]. Systematic descriptions were attempted for 50 species whose morphological features were clearly discernible. Three palynological zones which were from top to bottom were established. These zones are: Fereorinipollis nioericus Zone; Petitricolpites Sp.l Zone; Clavamonocolpites Sp. Zone. These zones are subdivisions of the Crassoretitriletes vanraadshocveri zone previously named by earlier workers in the area. Environmental interpretation based on the palynomorph assemblage and lithological characters indicated a transitional depositional environment. However, the relative abundance of Zonocostites ramonae at some intervals within the studied section pointed to a dominantly mangrove swamp environment.