GEOLOGICAL SECTION, BULAWAYO TO VICTORIA FALLS. 115 



Yictoiia Falls. When you itfe standing' at the foot of the 

 Palm Grove, you will be able to count in the opposite wall of 

 the gorge five successive basalt flows. The amygdaloidal top 

 of one flow, combined with the amygdaloidal base of the 

 succeeding- flow, forms a band on the M'all of the gorge which 

 weathers differently from the more regularly jointed and more 

 massive central portions of each flow. 



In the south-western corner of the Palm Grove gorge, 

 where the water of the Whirlpool dashes against the rocks, 

 may be seen what I take to be a small volcanic neck filled with 

 blocks of amygdaloidal basalt. 



Before leaving the Karroo rocks, 1 wish to draw your 

 attention for a moment to the two sets of trough faults — one 

 at Inyantue and one at Lukosi — by which the Karroo rocks 

 have been let doAvn in long, narrow strips into the crystalline 

 rocks. These structures are, in fact, miniature rift -valleys. 

 The Lukosi rift-valley I have been able to trace for about 

 20 miles on each side of the railway. There is a third and 

 narrower rift-valley to the south-east of the others, which 

 passes under tlie Kalahari sand. It should pass beneath the 

 railway betAveen Maliudi and Dett, but as the Kalahari sand 

 here covers the older rocks to a great depth, I have not been 

 able to insert it. 



The faults which formed these rift-valleys are almost 

 certainly of the same age as the Deka fault, and lend support 

 to the suggestion made some years ago by Mr. Molyneux that 

 the Victoria Falls basalts lie in a rift-valley, the north- 

 western edge of which is in Xorthern Rhodesia. 



The Kalahari beds consist chiefly of loosely-consolidated 

 sand of a red or white colour, which, at Malindi, has been 

 proved by a borehole to have a depth of 240 feet. At the base 

 of the sand t.here is, in places, a bed of chalcedon^^ in which 

 Mr. Molyneux has found gastropods and fresh-water plants, 

 determined by Mr. E. B. Xewton, F.G.S., to be of uppermost 

 Cretaceous age. In places, too, at the base of the sand is a 

 bed of pisolific ironstone, which was formerly used by the 

 natives for smelting iron. 



The Victoria Falls Hotel is situated on the edge of the 

 Kalahari sand, and at the foot of the sand-slope the chalcedony 

 crops out. The chalcedony nodules have been used by the 

 Bushmen for the manufacture of their stone implements, and 

 their working- sites may be found below the outcrop. 



The section shows very clearh' the unconformable nature 

 of the Kalahari beds, and the gradual rise in the base of the 

 beds from ;''.,000 feet at the Victoria Falls to just on 5.000 feet 

 in the neighbourhood of Bulawayo. It also shows a 

 pre-Kalaliari valley of the Zambesi, but the tributary Matetsi 

 seems to have cut a new course for itself not along- the line of 

 the pre-Kalahari valley. The Kalahari sand is the formation 

 upon which the teak and mahogany forests grow, which you 

 will pass through between the toD of the scarp beyond 

 Nyaraandhlovu and T)ett, and again between Fuller and Kesi. 



