Yol. 65.] KARROO SYSTEM IN NORTHERN RHODESIA. 435 



is difficult to determine. It is remarkable that the nearest high- 

 veld deposit, north of the Zambesi, that can be claimed as being of 

 the age of the coal series, is on the Kafue 150 miles away, and that 

 nowhere on the plateau, in the vicinity of the slopes to the valleys, 

 have I seen any vestige of Karroo beds. If they at any time 

 extended over a vaster area, it is remarkable that they should, 

 seemingly, have been cleared away so completely, for the blocks out 

 of the basal conglomerate lying at the head of the Muchinda Pass 

 show that this detritus is especially stubborn of removal. 



But there is evidence that Karroo beds once existed up to the 

 height of the escarpment, not only in the presence of the vestigial 

 pebbles just mentioned, but in the manner in which erosion is now 

 proceeding. The hanging valley of the Malenji, the course of the 

 Lusenfwa through the Kasafa outlier, and of the Lufua and Intauga 

 through the anticlinal domes, show that their courses were laid 

 out when the land-surface was at a much higher level. Again, 

 the narrowness of the belt behind the Machinga that is cut up 

 by watercourses, the deep denies of the rivers described, and the 

 erosion of their gorges back into the plateau when viewed in 

 contrast with their mature courses on the plateau, point to a time 

 when there was no need for their sudden precipitation to any 

 notable depth ; and the presumption is that the high level extended 

 across the areas of the Luano Valley. 



How much higher than this level the Karroo beds reached cannot 

 be stated, though it is probable that it was to some appreciable 

 thickness, and that search on the plateau will one day reveal vestiges 

 of these strata. For, subsequent to their deposition, folding, and 

 faulting, the whole country was planed off to a peneplain of 

 remarkable monotony, extending far away to the west, by which 

 Archaean and sedimentary masses shared a common reduction to one 

 level. By further causes, a radical change of the conditions under 

 which the land was planed down took place ; this subjected the 

 areas of Karroo beds to differential erosion, by which process the 

 synclinal folds of softer strata are being removed, to form the 

 remarkable trench-valleys of to-day, while the pre-Karroo complex 

 remains stubborn. 



From these changes in the surface-level, some measure of the 

 dislocation of strata by the Machinga Fault may be ascertained. 

 The Karroo beds at the base of the escarpment are those of the 

 latest series that is now displayed in the Luano, the Forest Sand- 

 stones being wanting. The system is at least 3000 feet thick, and 

 to this must be added the depth (2000 feet) of the Machinga wall. 



But the planing of the peneplain may have removed a further 

 thickness, and the total of the two figures just mentioned, namely 

 5000 feet, for the downthrow of the Machinga Fault, falls short 

 of the probable dislocation. 



Of the subsequent erosion of the clastic beds in the mid-Zambesi 

 Basin and the Luano Yalley much may be said, and the means by 



