168 F. P. Mennell— 



having a total thickness of about 150 feet, of which the uppermost 

 50 feet are fime and rather crumbly, while the lower 100 feet 

 are harder, more uniform and coarser in grain, and are characterized 

 by the presence of small scattered pebbles. They are, in fact, 

 identical in every respect with the " Escarpment G-rits " of the 

 Wankie coalfield further south, and of the intervening areas of 

 Goal Measures, of which the nearest is within about 20 miles. The 

 fact that no more than 50 feet of strata are lithologically similar 

 to the fine-grained Forest Sandstones, which are many hundreds of 

 feet thick elsewhere, is surprising, especially as they rest with apparent 

 conformity on the Escarpment Grits, but it is ia line with the remark- 

 able divergences seen among the Karroo strata as they are 

 followed eastward towards the coast. 



The lavas, of which the flows, as already noted, average about 

 100 feet in thickness, are uniformly basalts of the same type as seen 

 at the Victoria Falls. They are highly amygdaloidal at the base and 

 summit of each flow, and the amygdales as usual contain many 

 zeolites. Towards the eastern end of the basin the Kesha River cuts 

 through these rocks at a point where only two flows survive, and its 

 bed is in the Escarpment Grit until it gets on to the gneisses, across 

 which it makes its way into the Kafue, some miles to the north. 

 From the position of the block of basalts, etc., it seems clear that the 

 Kafue has just finished the removal by erosion of a great area of 

 basaltic lavas like those of the Victoria Falls, after first cutting a 

 gorge through them like that of the Zambesi, at the head of which 

 similar falls must at one time have existed. It is also evident that the 

 Kafue, like th.Q Zambesi, had its course largely determined by 

 synclinal structures in the Karroo rocks. Although the Karroo 

 rocks are often much faulted, the faulting has had no direct bearing 

 on the position of these rivers ; indeed, not far away, at the Kariba 

 Gorge, the Zambesi is in the ancient gneisses and schists, on the 

 upthrow side of a series of seven step faults which successively 

 bring up the Archaean rocks against the Karroo strata. It is hoped 

 to describe the structure of this interesting area at a subsequent date. 



Eastern Areas. 

 I. Tete. — The presence of Coal Measures (i.e. Lower Karroo beds) 

 at Tete, on the Zambesi, in Portuguese East Africa, has long been 

 known, and igneous rocks have been recorded from the same area. 

 It is quite possible that the occurrence of the lavas has also been 

 recorded, though I have not seen any distinct reference to them 

 myself, the volcanics to which reference is generally made being the 

 dolerite intrusions which are extremely numerous in the Tete district. 

 This latter fact is remarkable, as in Northern and Southern Rhodesia 

 no dyke traversing the Karroo strata has yet been definitely 

 identified. The lavas to which I refer are situated a few miles above 

 .the Lupata Gorge, and must be clearly distinguished from the 

 volcanic rocks of the gorge itself. The Karroo lavas are, as usual, 



