The Crystalline Rocks of the Kukuruku Hills (Southern Nigeria)

Abstract

In this paper a preliminary account is given of the crystalline rocks lying to the north of the Benin Sands of the Central Province of Southern Nigeria, and between 5° 20′ and 6° long. E. (for route, see map, p. 310). Comparison of this district with that of the Oban Hills goes to show that we have to deal with differences rather of degree than of kind. In each area we find a group of schists intruded into by a series of later gneisses of acid composition; in each the latter are associated with pegmatites and basaltic dykes. In the Kukuruku district (Owo, Otua, etc.) there is a striking development of quartz-schists, unknown up to the present in the Oban Hills; a difference to be naturally accounted for by the conditions under which the original sediments were deposited. The evidence for the intrusive nature of the gneisses of the Kukuruku Hills rests upon sections along the banks of the Ayi-ossi and the Ossi. The petrographical characters of the schists (quartz-schists, sillimanite-schists, etc.) show that they were originally sediments. A partial analysis of a very ferriferous mica-schist from Otua yielded: In many respects the gneisses recall those of the Eastern.. Province. Near Utchi in the Ogbese Valley the foliation of the gneiss trends N. 45° W. (true), and on the Ossi west of Iduani the trend of the foliation is approximately the same. Discussion (On The Three Foregoing Papers) Dr. J. W. Evans referred to the advantages of the system, by