﻿Vol. 66.] ON THE GEOLOGY OF N'YASALAND. 205 



concretionary bodies, formed by the partial cementation of the 

 sandstone by limonite. Owing to faulting, the actual thickness 

 of the Lower Sandstones is unknown, but must exceed 400 feet. 

 The Middle Division is about 30 to 40 feet thick. The thickness 

 of the Upper Division is also unknown, as the grits and sandstones 

 are covered uncon form ably by recent alluvium. 



Proceeding southwards along the edge of the gneiss, Karroo beds 

 are again seen exposed near Maulamba's village. A fine section is 

 obtained near here at the entrance to the Lufira Gorge. The Karroo, 

 as usual, is faulted against the gneiss on the west, and overlapped by 

 recent gravels and sands on the east. The series strikes roughly 

 north and south, and the dip varies from 10° to 30° eastwards. The 

 same three divisions can be recognized as at Kasante, and the rocks 

 are very similar in character. The Lower Sandstones, however, 

 contain pebbly bands, and the coals of the Middle Group are much 

 thinner and very earthy. The crystalline rocks on the west consist 

 of quartz-muscovite schists and gneisses, identical with those near 

 Kasante. 



Continuing southwards, the Karroo is again faulted out, but 

 reappears about 3 miles farther on, near Kasisi's village. To the 

 south of Kasisi an important fault, running in a north-easterly and 

 south-westerly direction, throws back the gneiss more and more 

 to the west. The Karroo now, as a rule, strikes north and south 

 against the fault and dips eastwards, so that the beds of the lowest 

 division are not met with until the Rukuru River is crossed in a 

 south-westerly direction. 



Between Kasisi's village and the Rukuru the upper grits and 

 sandstones form a series of hills followed on the east by low ridges 

 of limestone and calcareous mudstone, which run nearly due north 

 and south. The calcareous series disappears gradually under the 

 recent alluvium of the lake-plain. The sandstones and grits, men- 

 tioned above, belong entirely to the Upper Division. They are 

 usually felspathic, and sometimes micaceous in character. Thin 

 bands of reddish shale and mudstone with calcareous concretions 

 occur in this group. The limestone series consists of a considerable 

 thickness of compact, grey, argillaceous limestones, whiter limestones 

 of gritty texture, and grey mudstones, the last-named predominating. 

 Xear the Rukuru these are found resting on the lower gritty sand- 

 stones, which here contain lenticular seams of pebbles, and a band 

 of hard red shale with ill-preserved leaves of Glossopteris. 



The Karroo is more fully developed south of the Rukuru River 

 in the Mpata district (fig. 4, p. 206). It is separated off from the 

 northern area by an east-and-west line of fault, with a downthrow 

 to the south. The Mpata district, so called from the large village 

 of that name, covers an area of about 15 square miles. Its eastern 

 boundary is defined by the Ulamwe and Nyanja group of hills ; its 



