652 Geological Society: — 



The following rock- systems are described : — 

 5. Kalahari Sands, Chalcedonic Quartzite, and other surface-deposits. 

 4. Flaggy Sandstone of Boornka. 

 3. Batoka Basalts. 

 2. Wankie Sandstones and Coal -Measures (= Matobola Beds and 



? Escarpment Grits of Molyneux). 

 1. Fundamental Complex of Metamorphic and Igneous Eocks. 



(1) The Fundamental Complex was studied msita onlyat 

 one point, near the Wankie Coal-mine. The position of its outcrop 

 north of the Zambezi is inferred from the character of the river-borne 

 detritus in some of the stream-beds. 



(2) The Wankie Series consists of massive sandstones and 

 pebbly grits, containing boulders near the base, with intermediate 

 flaggy sandstones and shales with coal-seams. This series is 

 abruptly truncated on the south-east side, along the Deka River, 

 by a great fault which brings in the Batoka Basalts; but reasons 

 are given for supposing that beds of similar character reappear at 

 the northern margin of the Basalts, north of the Zambezi, beyond the 

 district examined. 



The Deka Fault is described in some detail, and its important 

 influence upon the structure of the country is discussed. It is 

 suggested that the ' Sijarira Quartzites' of Molyneux, of the 

 country farther to the north-east, may be only the indurated and 

 contorted sandstones that accompany this great fault. 



(3) The Batoka Basalts were found to extend unbrokenly 

 from the Yictoria Falls eastward to the mouth of the Deka, and 

 southward to the edge of the Kalahari Desert ; and it is shown that 

 they also cover a very wide area to the southward and westward of 

 the region traversed. They consist of a succession of massive lava- 

 flows and flow-breccias ; no intercalated sediments were found in 

 the districts examined, nor was any eruptive centre discovered. 

 Some curious structures observed in basalts are described ; and it 

 is remarked that the zigzagging character of the stream-gorges below 

 the Yictoria Falls is due to differential erosion along the strong joints 

 and fault-planes in these rocks, under the alternating conditions of 

 wet and dry seasons. 



The age of the Basalts is discussed, and it is considered that they 

 are probably Mesozoic, and may date back to the later stages of the 

 period of volcanic activity represented by the Storm berg Beds of 

 the more southerly part of the continent. 



(4) Some limited patches of Flaggy Sandstone, etc., seen near 

 the head of the Deka JBasin, appear to represent sediments newer 

 than the Basalts, and may be equivalent to part of the Forest- 

 Sandstone of Mr. A. J. C. Molyneux and Mr. F. P. Mennell. 



(5) The 'Kalahari Sands,' which cover large areas of the 

 plateau, occur mainly in broad low swells or ' bults ' of friable red 

 sand, now tree- clad. These sweep down to the Zambezi River in 

 the shallow valley above the Yictoria Falls, and cannot have been 

 accumulated under existing conditions. The author endorses 

 Dr. S. Passarge's view that they indicate a former period of greater 

 aridity than the present in the Central Basin. 



Some irregular patches of surface-quartzite and limestone, due 



