WORKING GROUP 2 
ALLUM 
75 
Fig. 4. Permeation gneiss near Ogbagda, Iwo Sheet, Nigeria 
Stereopair — Soil covered permeation gneiss near Inisa, Iwo Sheet, Nigeria 
A “flowing” effect will be noticed from north to south. This results from the parallelism of a 
large number of small lineaments such as second order tributaries, subdued ridges and the 
alignment of small trees and bushes. Field work shows that this “flowing” effect is parallel to 
banding, in the underlying permeation gneiss (fig. 4). 
Aerial photographs thus provide the means of tracing this banding rapidly over large areas and 
determining large structures such as major folds, even when the permeation gneiss is soil 
covered.