﻿212 MESSRS. A. E. ANDREW AND T. E. 0. BAILEY [May I9IO,. 



direction. They lie on an eroded platform of augen -gneiss or 

 foliated granite, which rises gradually westwards and occupies 

 the gap already described as existing south of the Kayuni Range.. 

 The lowest beds are well exposed in the dry bed of the Mpasi 

 (Nquarlewele) stream, and the Ruyuma or Kawala stream near 

 Sudje Hill. They consist of a series of whitish sandstones, coarse 

 boulder-beds, and finer conglomerates. In the Mpasi stream these 

 are associated with carbonaceous shale and interbedded coal-seams 

 lying rather above the main mass of conglomerates, These in turn are 

 overlain by a great thickness of felspathic sandstones and grits, with 

 bands of red mudstone in the lower half, and pebbly beds in the 

 upper. This upper division is faulted down to the east against 

 the Muoma ridge of gneiss. The Muoma Fault runs in a roughly 

 north-and-south direction and bifurcates to the north, thus enclosing 

 the narrow horst of gneiss already described. East of the Muoma 

 ridge the basal conglomerates are again exposed (section 2, fig. 9, 

 p. 218), and they here form the bed of the Rukuru River for about 

 5 miles, as also the lower slopes of a scar facing the stream. Above 

 the conglomerates comes a series of carbonaceous shales and mud- 

 stones with shaly coal. The actual scar is formed out of the hard 

 felspathic grits and sandstones of the Upper Division. These dip 

 eastwards, and eventually abut against the Nyika Fault. Tracing 

 this fault for some miles to the north, the lower beds are again 

 found exposed near Chimanga village on the Chipome River. These 

 consist of whitish sandstones, conglomerates, carbonaceous shale,. 

 and coal-seams. The beds frequently dip at high angles west- 

 wards, and the actual junction with the gneiss appears to be a 

 faulted one. 



From the foregoing description, it seems possible to divide the 

 Karroo of the Western Nyika area into the following divisions : — 



3. Upper Division ... Felspathic grits and sandstones, with beds of mud- 

 stone. Thickness = 3000 feet (?). 



2. Middle Division... Carbonaceous shales, coals, mud--j 



stones, and conglomerates. Thickness = 



1. Lower Division .... Conglomerates and whitish sand- | -'OO to oOO feet, 

 stones. J 



The only fossil obtained was a silicified tree-trunk in the pebbly 

 sandstones of the Upper Division, near Sudje Hill and close to the 

 Rukuru River ; but the general similarity of the series with that of 

 the Mwapo-Rukuru area leaves little or no doubt that it is of 

 Karroo age. 



It is obvious that the present position of the Karroo is due to 

 trough-faulting. The remarkable, almost wall-like edge of the 

 Nyika Plateau might be considered as an indication of the recent 

 age of the faulting. A closer examination fails to sustain this view. 

 The Rukuru Valley, for instance, shows a progressive development 

 of its eastern tributaries when traced down stream, after the manner 



