Arthur Holmes — Lateritic Deposits, Mozanibiqite. 531 



fragments of iron-stained gneiss in the lower layers of the deposit. 

 The general upward succession appears to be from unaltered gneiss 

 through moist disintegrated gneiss to similar material deeply stained 

 with a ferruginous cement. On this lay the lateritic earths, damp in 

 their lower levels, but dry above, and with a strong concentration of 

 the lateritic constituents at or near the surface. 



The laterite shows a striking disposition to lie in well-marked 

 bands, sometimes continuous but generally broken, parallel to the 

 strike of the underlying gneiss, or to the pegmatite veins which 

 penetrate the gneiss. It is found only on the gently undulating 

 plateau and never on the steep slopes or summits of the inselberg 

 peaks and mountain blocks which, as one proceeds westwards from 

 the coast, rise up abruptly in increasing numbers and altitude. The 

 plateau surface itself, which rises from sea-level at the coast to a 

 height of 1,000 feet at Nampula, to nearly 2,000 feet around the 

 Ribawe Mountains, and to about 3,000 feet in the neighbourhood of 

 the Namuli Peaks, is diversified by numerous low ridges traversing 

 the country parallel to the strike of the gneissic foliation, the 

 direction of which lies between N.E. to S.W., and N.N.E. to S.S.W. 

 (Fig. 1). These ridges have a ' dip ' slope which usually lies on the 

 west or north-west side, and an ' escarpment ' slope, the gradient of 



Banded Gne/ss 



Fig. 1. — Typical Section in Maravi's country, north of the Mitikiti Eiver, 

 illustrating the occurrence of laterite on the escarpment slope of a ridge. 



which, however, is only a little steeper than that of the dip slope. 

 The prevailing dip of the foliation and banding, especially in the 

 eastern part of the country, is in a direction away from the sea, so 

 that when the angle of dip is low, the truncated foliation of the gneiss 

 is more plainly visible on the escarpment slope than on the dip slope, 

 wherever an exposure is encountered. The first and simplest feature 

 in the distribution of laterite in Mozambique is that it frequently lies 

 in bands near the crests of the ridges on the escarpment side (Fig. 1). 

 It thus comes in many places to have the appearance of being actually 

 interbedded with the gneiss. Mr. Wray records a good example 

 which he found between the Mrupi Mountains and the Luli Kiver. 

 There he traced an important band, continuous for a mile and a half, 

 between two hard outcropping bands of coarse hornblende gneiss. 



Bands of laterite are also commonly found near the sides of small 

 watercourses, the majority of which dry up during several months of 

 the year. Mr. Wayland was impressed with the fact that many of 

 the bands lie on the eastward side of the gullies, and that where 

 laterite is found on both sides the development is greater on the east- 

 ward side. My own field maps indicate several such occurrences 

 which are, I think, to be correlated with the predominant direction 

 of dip of the foliation of the gneiss, for in such cases the dip is 



