Miospore biozonation of cenomanian - santonian succession in Famo-1 well, Gongola Sub Basin, Upper Benue Trough, Nigeria

Abstract

The Early Cretaceous succession penetrated by Famo-1 well in Gongola sub Basin, Upper Benue Trough, Nigeria were analyzed for its palynological content. This investigation produced significant Pollen and Spore and the assemblage reveals the dominance of angiosperm Pollen grain and pteridophytes spore. Gymnosperm pollen was scarce and less varied. The studied interval penetrated a sequence of sandstone, sandy shale and mudstone occurring at different intervals in the studied section of the well. Established on the stratigraphic distribution of the palynomorphs recovered from Famo-1 well, three informal assemblage palynozones covering the Early Cretaceous were identified. The zones are: Assemblage Zones I & II (Cenomanian); Assemblage Zone III (Turonian - Santonian). The different zones signifies a time stratigraphic unit comparable to the identified lithostratigraphic units penetrated by the well. The age (Cenomanian - Santonian) determinations are based on the known stratigraphic ranges of pollen and spores and their relative stratigraphic positions. Data from the studied well revealed that there is relatively higher frequency of the land derived pollen and spores compared to marine palynomorph abundance, which suggests a paralic condition of continental to shallow marine environment. The shallow marginal marine environment is further sustained by the presence of foraminifera test linings at some depths which are indicative of marine palaeoenvironment (inner neritic environment). Interpretations from the spore and pollen assemblages reveal sediment deposition took place in a wet to arid climate condition in marginal marine to nearshore environment.

Keywords: Palynology, Gongola sub Basin, Cretaceous, Famo-1 Well