Sedimentological characterization and palynological age dating of the pre-bima and bima formations in bornu basin, North-Eastern Nigeria

Ola-Buraimo A.O¹ and Oluwajana O.A²

¹Department of Earth Sciences, Ladoke Akintola University of Technology, Ogbomoso, Nigeria

²Department of Geology and Applied Geophysics, Adekunle Ajasin University, Akungba Akoko, Nigeria

*Correspondence   Author   E-mail:   rolaburaimo@yahoo.com

Accepted 30 May, 2012

Sedimentological analysis was carried out on 244samples obtained from Murshe-1 well located in Bornu Basin, Nigeria. Nine different lithofacies units were established including heterolith of sand and shale, sand, shale, gypsiferousshaly sand, shalygypsiferous sand, gypsiferous sand/sandy gypsum, gypsiferous shale/shaly gypsum, gypsum and claystone. The Pre-Bima is characterized by sand/shale heterolith restricted to the lower part (2980-3630m); while the presence of gypsum in heterolith of sand and shale is of various proportions. The sand grains vary in size from fine to pebble, angular to rounded and poorly sorted; suggested to be deposited in fluviomarine to marine systems. The Pre-Bima is dated Albian age based on pollen assemblages such as Steevesipollenitessp, Cretaceiporitesspp, Forma PO 304 Lawal, Ephedripitesmulticostatus, Afropollisjardinus, Gnetaceaepollenitessp, Galeacorneacursea, Leptolepiditesverrucatus and Patellasporitesdistaverrucosis. The Bima Formation is predominantly dark grey to black shale with interbeds of gypsum deposited in marine setting. It is defined palynologically by co-occurrence of Elaterosporitesklaszi, Ephedripites sp1, Ephedripites sp3, and Hexaporotricolpitesemelianovi, dated Cenomanian age and deposited under marine condition. Both the Pre-Bima and Bima Formations are here referred to as Bima Group.

Keywords: Lithofacies, Fluviomarine, Heterolith, Formation and Group