Biostratigraphy of Section of Murshe-1 Well, Bornu Basin, Northeastern Nigeria

Abstract

Biostratigraphic work using palynology was undertaken in order to re-assess the lithofacies, chronostratigraphy and paleoenvironment of deposition of sediments in Murshe-1 well, Bornu Basin, northeastern Nigeria. Two hundred and ninety ditch cutting samples obtained from the exploratory well Murshe-1 located in Bornu Basin were used for lithologiacal description. Twenty one (21) samples were selected at 27.4m interval for palynological analysis. The samples were analyzed under microscope for lithologic and palynological description. The latter were taken through sediment digestion and floatation of macerals. Various lithofacies relationship is present such as black fissile shale, sandy shale, intercalated fissile shale with gypsum, conglomeratic sandstone, mudstone and claystone; while five palynological zones are established. The palynological zones established are Triorites africaensis assemblage zone 1 characterized by the co-occurrence of Classopollis brasiliensis, Triorites africaensis, and Retimonocolpites sp; dated Turonian. Zone 2 is dated Senonian to Campanian based on the assemblage of Syncolporites sp, Milfordia sp, Mauritiidites crassibaculatus, and Aequitridites sp. The Spinizonocolpites baculatus assemblage zone 3 is defined by the co-occurrence of Longapertites marginatus, Periretisyncolpites sp, Trichotomosulcites sp, Auriculiidites sp, Foveotriletes margaritae, Spinizonocolpites baculatus, Monocolpites marginatus, Striatopollis bellus and Retidiporites magdalenensis; depictive of Maastrichian age. The Proxapertites cursus assemblage zone 4, dated Paleocene is distinguished from the older Maastrichian sediment based on the paucity of palynomorphs and the appearance of Verrutricolporites sp. Zone 5 is dated Eocene-Younger based on the co-occurrence of Monoporites annulatus, Retibrevitricolporites protrudens, Longapertites vernendenburgi and Lycopodium phlegmaria.