Lithostraigraphical and palynostratigraphical studies of Igbomotoru-1 Well, Niger Delta

Abstract

Palynological investigations were carried out on 41 side wall core samples of Igbomotoru-1 Well in the Niger Delta. The samples were from the intervals 1,123 to 3,583 m. A lithostratigraphical interpretation of the well was made by studying gamma ray logs, the drilled samples and lithologic descriptions made available by the Shell Petroleum Development Company of Nigeria (SPDC). It resulted in the delineation of four informal lithostratigraphical units (A, B, C, D) which show lithological characters of the Benin and Agbada Formations. The studied interval was assigned Middle Miocene to Upper Miocene age on the basis of such age diagnostic miospores as Crassoretitriletees vanraadshoveni, Peregrinipollis nigericus, Zonocostites ramonae and Multiareolites formosus. Three palynological sub-zones which were from top to bottom and subdivision of Crassoretitriletes vanraadshooveni zone of earlier workers in the area were established. These are: Peregrinipollis nigericus sub-zone Retitricolpites sp. 1 sub-zone Clavamonocolpites sp. sub-zone Paleoenvironmental analysis based on the palynomorph assemblage and lithological characters indicated a transitional depositional environment. However, the relative abundance of Zonocostites ramonae (cf. Rhizophora sp.) at some levels in the studied interval pointed to a dominantly mangrove swamp environment.