Foraminiferal Biostratigraphic studies of Miocene Strata of Well 01, Shallow Offshore, Western Niger Delta, Nigeria

Abstract

The foraminiferal biostratigraphic analysis of the interval (6000- 11250 feet) of well-01 shallow offshore western Niger Delta was conducted based on the study of one hundred and twelve ditch cutting samples. Standard method of processing foraminiferal was employed. The study aimed to establish biozonations, age of the sequence and to decipher environment of deposition of the sediment. Moderately rich and diverse foraminiferal species were recorded. Ninety six foraminiferal species were identified, of these 88 species (92 %) are calcareous while the remaining 8 species (8 %) are arenaceous. Of the calcareous forms, 59 % (57 species) are benthics, while the remaining are planktics. Planktic zones established in this study are Orbulina universa zone (N9), Globorotalia peripheroacuta zone (N10), while Brizalina mandoroveensis and Uvigerina sparsicostata were defined as benthic zones. The established zones were dated middle Miocene, below Orbulina universa zone is assigned early Miocene (N8) due to LDO (Last Down hole Occurrence) of Orbulina universa which defines early Miocene/Miiddle Miocene boundary. The sequence of the well was deposited in inner neritic - outer nertic environments based on the occurrence of Ammonia beccarii, Lenticulina grandis, Eponides eshrra, Lenttculma spp, Uvigerina sparsicostata