430 ME. A. J. C. M0LYNEUX ON THE [-A-Ug. I909, 



again, along an outcrop of fine vermilion sandstones, with an in- 

 terbedded white stratum. White concretionary siliceous kernels, 

 or tubes of ordinary pencil size, also occur in the red beds. The 

 dip is 10° south — conformable with the general dip thereabouts. 



The altitude of these beds is about 1450 feet. Forest Sandstones 

 cover the apex of the Matabeleland plateau at 4500 feet, where 

 they dip northwards, but have overlapped the older Karroo beds and 

 lie directly on the complex. The latest Karroo beds, the Forest 

 Sandstones, thus seem to have shared in the depression of the basin 

 in post-Karroo times. This supports Mr. Lamplugh's observations 

 on the Deka Fault, which is marked by the downthrow of even 

 later strata — the Batoka Basalts. 



The Volcanic Series. 



So far as my knowledge goes, this is not represented in the 

 Lufua-Losito region or the Luano Valley, nor have any intrusions 

 penetrated the Karroo strata. 



The basalt-sheet, so remarkably developed around the Victoria 

 Falls,' extends into Northern Rhodesia, as far as the slopes of the 

 plateau about 30 miles from the river. Westwards it appears to 

 stretch far up the Zambesi, in which direction there is much to 

 learn as to the part played by this series in the physiography of the 

 upper reaches. 



The origin of the loose sand that overlies the basalt-sheet in 

 rolling hills 2 (the 'Kalahari Sands' of Passarge) is probably in the 

 saccharoidal quartzites of the Chasonsa Series of the complex. The 

 associated limestones and schists are seen to contain the same 

 granular quartz, and all these rocks weather to a great depth, 

 yielding a sandy subsoil 5 to 10 feet thick. Such sandy areas, 

 covered with wide-spreading forests, are of great extent in Trans- 

 Zambesia, and the transport of the debris to the depressed sheet 

 of the Batoka Basalts would not be attended with much difficulty. 



IV. Structural Geology. 

 Post- Karroo Movements. 



The rocks of the Karroo System are much fractured and jointed, 

 and faults of varying amount of displacement are frequently en- 

 countered. At Chisalisali two nearly parallel faults have lowered 

 a tongue of the upper sandstones into the coal-measures — a drop of 

 400 feet. The cracks show infilling of calcite in six parallel veins, 

 each a quarter of an inch thick, denoting a succession of movements. 

 These faults are radial, and cut across the strike. 



The lines of greatest displacement, however, are tangential to the 



1 A. J. C. Molyneux, ' The Physical History of the Victoria Falls ' Geogr. 

 Journ. vol. xxv (1905) p. 400. 



2 G. W. Lamplugh, ' The Geology of the Zambezi Basin around the Batoka 

 Gorge (Rhodesia) ' Quart. Journ. Geol. Soc. vol. lxiii (1907) pp. 201-202. 



