PALYNOMORPH DISTRIBUTIONS, BIOSTRATIGRAPHY AND PALEOENVIRONMENTAL STUDIES OF FIKA SHALE, UPPER BENUE TROUGH, NIGERIA

Abstract

A total of thirty (30) outcrop samples retrieved from the Upper Ridge and West Q sections at Ashaka, Fika Shale Upper Benue Trough, Nigeria were studied using Palynomorphs content to determine the biostratigraphy, age and paleoenvironment of deposition. The formation is characterized by the intercalation of limestone (with ammonites, bivalves and gastropods) and shale. The methodology involves a digested crushed samples treated in succession with hydrochloric acid to remove carbonates, hydrofluoric acid to remove silicate and nitric acid for oxidation before being mounted on the slide. Identification is achieved with the use of light transmitted microscope. The palynomorph assemblages include Longapertites marginatus, Longapertites microfoveolatus, Retimonocolpites obaensis, Monocolpites marginatus, Echitriporites trianguliformis, Laevigatosporites sp, Verrucatosporites . sp, Monoporites annulatus, Longapertites sp, Proxapertites cursus, Retibrevitricolporites protrudens, Verrutricolporites rotundiporus, and Leiosphaeridia sp. Dinoflagellate cysts including Operculodinum centrocarpum, Lingulodium machaerophorum and marine microforaminifera wall lining were also recorded which can be used for biozonation and paleoecology. The total preserved palynomorph assemblages at Upper Ridge and West Q is 136 species, comprising 72 species of pollens, 42 species of spores and 22 species of dinoflagellate cyst. The forms retrieved from the sections are shallow marine forms typical of Maastrichtian age.