[01] Efosa Udinmwen, Department of Geology, University of Calabar, Calabar, Nigeria.

The study area is part of the western flank of the Ikom – Mamfe basin and contains sedimentary rocks which are made up of basically sandstones with minor mudstone, limestone and shale. Thin section analysis show that the sandstones are probably lithic sub-arkosic sandstone with a parent material most likely of igneous or metamorphic origin. The limestone and mudstone occur as thin beds within sandstone and the shales are baked in some cases. Sediments in the study area were probably deposited in high and low energy environments characterized by shallow and deep marine transgression events which led to the deposition of limestone and black shale respectively. The bedding planes in the sedimentary rocks dips gently and are cut by fractures oriented in the NW – SE/ESE – WNW, NNW – SSE, ENE – WSW and NNE – SSW directions. The fracture characteristics support the occurrence of two episodes of deformation in this basin.

Ikom – Mamfe Basin, Fracture, Sandstone, Limestone, Shale

[01] Petters, S. W., Okereke, C. S. and Nwajide, C. S. Geology of the Mamfe Rift. In: Matheis, G. and Schandelmeier, H., Eds., Current Research in African Earth Sciences, Balkema, Rotterdam, 1987, 299-302. [02] Nguimbous-Kouoh, J. J., Takougam, E. M. T., Nouayou, R., Tabod, C. T. and Manguelle-Dicoum, E. Structural Interpretation of the Mamfe Sedimentary Basin of Southwestern Cameroon along the Manyu River Using Audiomagnetotellurics Survey. ISRN Geophysics, 2012, 1–7. [03] Obi, D. A., Obi, E. O and Okiwelu, A. A. Basinal configuration and intrasediment intrusives as revealed by aeromagnetics data of south east sector of Mamfe basin, Nigeria. IOSR Journal of Applied Geology and Geophysics, 2013, 1 (5), 1–8. [04] Reyment, R. A. and Murner, N. A. Cretaceous transgressions and regressions exemplified by the south Atlantic. Spec. Bull. Paleout. Soc. Japan. 1977, 21, 246-261. [05] Fairhead J. D., Okereke C. S. and Nnange J. M. Crustal structure of the Mamfe basin, West Africa, based on gravity data. Tectonophysics, 1991, 186: 351-358. [06] Hossain, M. T. Geochemistry and Petrology of the Minor Intrusives between Efut Eso and Nko in the Ugep area of Cross River State, Nigeria. Jour. Min. Geol, 1981, 18 (1): 42-51. [07] Udinmwen, E. The geology of Ekori and environs and structural analysis of Ikom and Ohana basalts Unpublished B.Sc Project, 2012, Department of Geology, University of Calabar, p. 121. [08] Umagu, C. I. Cretaceous intrusives of part of the Ikom – Mamfe basin: Petrographic and structural studies. Unpublished M.Sc Thesis, University of Calabar, 2015. p156. [09] Oden, M. I., Egeh, E. U and Amah, E. A. The Ikom – Mamfe basin Nigeria: A study of fracture and mineral vein lineament trends and Cretaceous deformations. Journal of African Earth Sciences. 2015, 101; 35–41. [10] Oden, M. I., Udinmwen, E and Esu, E. O. The dolerites of Cross River State (DCRS): physical and mechanical properties. Environment and Natural Resources Research, 2013, 3 (1), 135–143. [11] Etuk, E. E., Ukpabi N. Ukaegbu, V. U., Akpabio I. O. Structural evolution, magmatism and effects of hydrocarbon maturation in the lower Benue trough: A case study of Lokpaukwu, Uturu and Ishiagu. Pacific Journal of Science and Technology, 2008, 9 (2), 526–531. [12] Oden M. I, Umagu C. I, Udinmwen, E. The use of jointing to infer deformation episodes and relative ages of minor Cretaceous intrusives in the western part of Ikom – Mamfe basin, southeastern Nigeria. Journal of African Earth Science. 2016, DOI:10.1016/j.jafrearsci.2016.02.010. [13] Bassey C. E., Eminue, O. O. and Ajonina, H. N. Stratigraphy and depositional environments of the Mamfe Formation and its implication on the tectonosedimentary evolution of the Ikom-Mamfe Embayment, West Africa. Central European Journal of Geoscience. 2013, 5 (3), 349–406. [14] Njoh, O. A., Nforsi, M. B. and Datcheu, J. N. Aptian- Late Cenomanian Fluvio-Lacustrine Lithofacies and Palynomorphs from Mamfe Basin, Southwest Cameroon, West Africa. International Journal of Geosciences, 2015, 6, 795-811.