ISO ME. G. W. LAMPLUGH ON THE [May I907, 



whatever its original course may have been, its present direction 

 is clearly determined by this hard barrier. 



Nor is the influence of the fault likely to be confined to the 

 Deka valley, for it is highly suggestive that the great northerly 

 bend of the Zambezi itself east of the Deka confluence should 

 coincide very closely with the position and direction which this 

 fault will have if prolonged north-eastward. That it is indeed thus 

 prolonged is supported by travellers' records regarding the Gwai 

 River near its confluence with the Zambezi : from the descriptions 

 of Chapman 1 and Mohr 2 we gather that the sombre gorge of the 

 Gwai at some little distance above the confluence is eroded through 

 massive sandstone, while the great trough of the Zambezi between 

 the mouths of the Gwai and the Deka appears, from the accounts 

 given by Chapman 3 and Major A. St. H. Gibbons, 4 to lie within the 

 basalts ; and the following sentence seems to show that Chapman 

 struck the actual fault-line at a short distance south of the 

 Zambezi : — 



'A little valley coming into the Gwai, half a mile north of this [referring to 

 the place where he reached the Gwai], seems to be the dividing point of the 

 large square blocks, layer on layer, of hard red sandstone.' ( Op. cit. p. 193.) 



Furthermore, I am inclined to think that we have some evidence 

 suggesting the continuation of the fault to the north-eastward far 

 beyond the Gwai. In his account of the sedimentary rocks of 

 Southern Rhodesia, Mr. Molyneux describes, under the term of 

 ' Sijarira Series,' a great series of quartzites, indurated shales and 

 current-bedded sandstones which form a bold hill-range (the Sijarira 

 Range) overlooking the Zambezi flats some 70 or 80 miles east of 

 the Gwai. 5 These deposits he believes to occur beneath the 

 Matobola Beds (coal-measures), which are supposed to rest upon 

 them in strong unconformability. Mr. Molyneux several times 

 makes particular reference to the evidence for crushing, faulting, 

 and induration in the ' Sijarira Series'; for example, he remarks: — 



' Where the quartzites or indurated rocks occur, it may often be noticed that 

 there is a fault-fissure or displacement, and the axes of these movements take 

 a north-easterly direction, or at right angles to the dip. Thus at Ohongolo the 

 rocks are indurated on either side of a dyke of shale-and-sand stone crush- breccia. 

 At the Lubu are parallel dykes of crush-breccia, made up of angular blocks of red 

 sandstone, cemented by secondary white silica ; and at many other localities it 

 is noticeable that movements have taken place along lines following a north- 

 easterly direction, and have crushed the rocks into angular fragments, now 

 cemented together. . . . 



1 ' Travels in the Interior of Sou.th Africa' vol. ii (1868) pp. 193 & 212. 



2 ' To the Victoria Falls of the Zambesi ' 1876, pp. 297 & 302. 



3 ' Travels in the Interior of South Africa ' vol. ii (1868) p. 191. The rocks 

 ' of a stratified or laminated appearance,' externally very black, and internally 

 yellowish-brown, are probably the curious platy basalts presently to be described 

 (see p. 193). The rocks containing agates, and those of ' a scaly appearance, like 

 the scales of a bulb or onion,' are evidently basalts. 



4 • Africa from South to North through Marotseland ' vol. i (1904) p. 93. 



5 Quart. Journ. Gleol. Soc. vol. lix (1903) pp. 269-79, & sections, pi. xix. 



