Palynostratigraphy and Age of the Sequence Penetrated by the Kolmani River 1 Well in the Gongola Basin, Northern Benue Trough, Nigeria

Abstract

Sediments from the Kolmani River -1 well in the Gongola Basin, Northern Benue Trough, Nigeria, have been analyzed for palynomorphs from 900 ft to 9140ft. The main lithologies encountered in the well consist of sandstones, sandy shales, mudstones and siltstones. The result of the pollen analysis shows that angiospermous pollens and pteridophyte spores dominate the five palynological Assemblage Zones delineated in the well. Each zone represents a time stratigraphic unit.correlatable to the identified lithostratigraphic units penetrated by the well. The Aquilapollenites minimus Assemblage Zone (Late Maastrichtian) correlates with the Kerri Kerri Formation. The Longapertites marginatus Assemblage Zone (Early Maastrichtian – Late Campanian) correlates with the Gombe Formation. The Dictyophyllidites harrisii Assemblage Zone (Early Santonian), the Syncolporites subtilis Assemblage Zone (Coniacian) and upper part of the Steevesipollenites binodosus Assemblage correlate with the Pindiga Formation while the lower Steevesipollenites binodosus Assemblage Zone (Turonian – Cenomanian) correlates with the Yolde Formation. The absence of the Late Santonian confirms the presence of the Santonian unconformity in the northern Benue Trough. Based on quantitative and qualitative biostratigraphic and sedimentological analyses, the overall depositional environment of the analyzed interval of the well varies from coastal plain/estuarine to open marine.