420 MR. A. J. C. MOLYNEUX ON THE [Aug. 1 9^g r 



holding the soft Karroo strata, filled and even covering the 

 anticlinal arches at the time when the course of the Lufua was. 

 determined. By erosion the clastic beds are being removed from 

 the valleys, and the cutting of the intervening gorges proceeds 

 pari passu. The evidence of folding is set forth later (p. 433). 



The Intanga is a tributary of the Lufua, but its valley is 

 strikingly different from that of the latter, and under its various 

 local names might be looked upon as the true main river. It runs 

 in an open and gradually descending valley, meeting the margin 

 of the Karroo at an altitude of 500 feet over that of the contact 

 in the Malembi basin, that is. 285-5 feet — an unusual elevation for 

 the Karroo hereabouts. The Intanga then passes through a rocky 

 defile of gneiss to traverse a further basin of Karroo, and is there 

 known as the Mutema. 



Parallel and on its left bank is the Inyanga range, steep and 

 high, which, viewed from a distance, possesses all the frontal 

 appearance and features of the Machinga. This range merges 

 towards the north-west into the Kahunga plateau, of which it is 

 the typical abrupt escarpment-edge. 



The Losito River is situate north-eastwards of the previous 

 feature, and is the last valley that will be described as bearing 

 upon the subject of this paper. Like the others it rises on the 

 plateau, at 4000 feet, and quickly makes for itself a narrow gorge 

 in the bedded Archaean rocks, striking east 23° south. Its valley- 

 scheme resembles that of the Lufua, and it debouches on to the 

 Zambesi Karroo plains through the escarpment-line near Muti Peak. 

 The schists traversed by its upper course strike parallel with it, and 

 anticlinal folds in the vicinity have axes pointing south-eastwards. 



From the plateau-step the Losito meanders along the contact 

 between the complex and the Karroo beds, the latter here dipping 

 southwards. Opposite Murorobela Mountain it launches out for 

 a course to the Zambesi, 18 miles away, traversing a flat, thorn- 

 covered country, with much recent alluvium. Exposures of rock 

 showed sandstones possessing lithological features that have much 

 in common with the Forest Sandstone ; and, if this correlation be- 

 established, we shall have here further evidence of the lowering 

 of the Zambesi basin extending into post-Karroo times. 



The Losito-Zambesi juuction lies at 1376 feet above sea-level. 



Generalizing the surface-features of the Lufua, Intanga, and 

 Losito, I find that they are determined by structure, in that the 

 valleys run parallel with the cleavage, the axes of folding, and the 

 strike of the massive quartzites and limestones of the complex. 

 These are the dominating causes of the Inyanga range. There is 

 this variation from analogous causes in the Luano, that here they 

 have a north-westerly and south-easterly direction instead of the 

 east-north-easterly direction of the other. 



