Palynological and Paleoenvironmental Study of Paleogene in Bende – Umuahia, Niger Delta Basin, Nigeria

Abstract

Palynological and paleoenvironmental study of outcrops exposed around Bende and Umuahia areas were carried out to re-evaluate its age and reconstruct the environment of deposition. Palynological analysis of the sediments was done by using conventional method of 40% concentrated Hydrofluoric acid maceration to determine the age and paleoenvironment of the area. Lithological units encountered were carbonaceous shale, sandstones, mudstones and limestone. Age determination/correlation was based on occurrence of stratigraphically significant age diagnostic palynomorph assemblages. Imo Formation was dated Middle – Late Paleocene with the following index fossils assemblage, Proxapertites operculatus, Echitriporites trianguliformis, Retibrevitricolpites triagulatus, Spinizonocolpites baculatus, Scabratriporites simpliformis, Mauritidiites crassibaculatus, Bombacidites sp., and Grimsdalea polygonalis. Ameki Formation was assigned Early-Middle Eocene based onMonoporites annulatus, Proxapertites cursus, Retistephanocolpites williamsi,Ctenolophonidites costatus, Spinizonocolpites echinatus, Psilatricoplorites crassus, Psilatricolporites operculatus, Retitricolporites irregularis, and Striatopollis sp. Ogwashi Formation was dated Late Eocene-Oligocene on the basis of the age diagnostic sporomorphs assemblage, such as, Verrucatosporites usmensis, Laevigatosporites ovatus, Chenopodipollis sp., Retibrevitricolporites sp., Psilastephanocolporites sp., and Racemonocolpites hians. The environmentally significant palynomorphs species indicate that Imo Formation was deposited in a tidally influenced shallow marine estuarine setting, while Ameki Formation was deposited in open shallow marine to estuarine-lagoonal settings. Ogwashi Formation was deposited between upper to lower deltaic settings. The palynological study suggests Formtions of Paleogene Age while the paleoenvironment is Deltaic to Shallow marine