[01] Efosa Udinmwen, Department of Geology, University of Calabar, Calabar, Nigeria. [02] M. I. Oden, Department of Geology, University of Calabar, Calabar, Nigeria. [03] E. E. Ukwang, Department of Geology, University of Calabar, Calabar, Nigeria. [04] E. S. Edu, Department of Geology, University of Calabar, Calabar, Nigeria.

The Ikom columnar basalt is found in the western part (Nigerian sector) of the Ikom – Mamfe basin. This polygonal basalt shows a distinct geometry with a colonnade which has well defined polygonal faces overlain by an entablature with irregular geometry. The mineralogy of both the colonnade and entablature are similar containing plagioclase, pyroxene and olivine. These polygons show the dominance of pentagonal (5 – sided) and hexagonal (6 – sided) polygons with the preponderance of pentagonal (5 – sided) polygons. The low axial ratios and the non – preferential orientation of the long and short axes of the polygons strongly suggest a strain free or low strain condition of crystallization of this basalt. The fractures in the basalt are high angled and oriented in the NE – SW direction which is not related to known tectonics of the Ikom – Mamfe basin thus they probably developed from local processes related to overburden pressure. The overall geometry and exposure of the Ikom columnar basalt makes it a relevant site for geotourism.

Ikom, Basalt, Columnar, Polygonal, Ikom – Mamfe Basin

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