Biostratigraphy and Paleoenvironment of Bolivina Fauna from the Niger Delta, Nigeria

  •  E. O. Obiosio    


A rich Bolivina assemblage occurs in the onshore Tonjor-1 well of Niger Delta; eighteen species are reported for the first time. Some index planktonic foraminifera allowed a late Early Eocene age assignation, in addition to some Bolivina species that are known to be restricted to samples from the studied intervals. The Bolivina species recovered permits the subdivision of the succession into one taxon and interval range zones respectively and two concurrent subzones. The interval zone is Bolivina ottaensis Reyment; while the taxon zone is Bolivina attenuata Cushman. The concurrent sub-zones are Bolivina foliacea Sellier de Civrieux and Bolivina jacksonensis Cushman and Applin. The planktonic foraminifers associated with the bolivinids are namely, Acarinina pentacamerata (subbotina), A. psuedotopilensis (Subbotina), Pseudohastigerina wilcoxensis (Cushman and Ponton) and Globigerina officinalis Subbotina which permits the late Early Eocene dating of these zones. Stratigraphic diversity variation of the bolivinds allowed the recognition of late Early Eocene marine transgression which correlates with the global timing of Early Eocene transgression. The presence of strong costae, and larger test suggests a deposition in a well oxygenated slope to bathyal environment.

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