A photogeological study of the fold structure in okemesi area, Nigeria.

Abstract

The Okemesi fold, situated in southwestern Nigeria, is one of the most identifiable geological structures in the basement complex. It is a manifestation of Late-Precambrian deformation of metasediments which have been heavily fractured and sheared in places.
Aerial photographs covering about 150km2 of the fold belt were selected for the study because of their large scale and good resolution for structural delineation. A total of 175 fractures were extracted with a cumulative length of about 155 kilometers. They are in three main classes of azimuths: 011o-020o, 021o-030o and 101o-110o.
Results indicate the existence of a series of faults that offset the fold trend. Field observations also show that schists and schistose quartzites display strong foliation and shearing which are indicated by displacements along sub-parallel planes. Faulting in the area probably post-dated the folding episode as indicated by the Itawure Fault which separates the Okemesi fold into double-plunging halves; one towards the north and the other towards the south. These structures are observed to be the main factor controlling the drainage pattern in the area. The area of study displays a series of folds which were possibly generated by overthrusting of low-dipping rocks and subsequent fracturing that resulted in the plunging of the fold axis.


Journal of Mining and Geology Vol. 43 (2) 2007: pp. 125-130