232 Heporfs and Proceedings — Geological Societij of London. 



tlie pebbles into one another is accounted for by the soft nature 

 of the schists and limestones, which would have been removed in 

 the internal movement before consolidation. 



In the Lukasashi and the Luano there is a general dip of the 

 strata north-westwards, that is, towards the escarpment, and 

 evidence of minor anticlinal and synclinal folds along east-north-east 

 axes. By a combination of these the Karroo deposits become 

 lowered from plateau level on the south, towards the north-west 

 culminating in a great downthrow fault along the foot of the 

 Machinga. 



Nowhere on the plateau in the immediate vicinity of the valley 

 walls have Karroo beds been found, and if they did once extend 

 there it is remarkable that they should have disappeared. But it 

 is certain that the valleys were at one time filled almost to plateau 

 level, as the rivers pass through Archsean inliers by deep clefts, and 

 must thus have laid out their courses before such, hard masses rose 

 from the Karroo beds by erosion of the latter. Also the comparatively 

 late times in which the Machinga escarpment was laid bare, and 

 the rejuvenation of the Lusenfwa River, etc., suggest a complete 

 filling of the valleys. 



It is thus possible that the Karroo beds extended over a part 

 of the plateau, and were included in the folding and faulting 

 movements already mentioned. Subsequently, by some continuous 

 agency the whole surface was planed off to a plateau of remarkable 

 monotony ; and on a further radical change of conditions taking 

 place, erosion of the softer Karroo strata set in by which the 

 present valleys are again reaching a plane of denudation. 



The facility with which atmospheric waters and acids attack the 

 sediments is notable, and decomposition extends to 100 feet in 

 depth over the flat regions of the plains. 



The author suggests that the trough vallej's of clastic rocks merely 

 follow the axis of pre-Karroo and post-Karroo movements, trending 

 in three directions. The Luano and part of the Zambesi course 

 agree with that of the folds and cleavage of the complex, certain 

 ranges of hills, and the Machinga Pault (east-north-east) ; a second 

 (south-easterly) trend is that of the Kafue, Losito, Inyanga range, 

 and Lufua, and the folds and cleavage of the complex in these 

 regions ; while the third follows the dominant direction of the great 

 tectonic movements of South Africa (north-east). Mr. L. A. Wallace 

 has noted that the Luangwa and mid-Zambesi are on this strike, 

 and Mi'. Gr. W. Lamplugh has suggested a northerly extension of 

 his Deka Fault. A distance of 800 miles thus displays movements 

 that commenced in pre-Karroo periods, and have repeated themselves 

 since the Karroo time. 



Fossils from the areas described support the previous allocation 

 of the deposits to the Permo-Carboniferous and to the Karroo System 

 of South Africa. Notable specimens are members of the Glossopteris 

 flora, including pith-casts of Sc]ii%oneura, carapaces of Ustheria, 

 ostracods, and fragments of bone, fish scales, and teeth. 



Palaeolithic stone implements (axe-heads) were found at separate 

 localities on the surface, about the latitude of 14° 50' S. 



