VOLCANIC PIPES 369 



are in contact with the volcanic rock itself. The shat- 

 tering of the quartzites extends for about one hundred 

 feet from the southern limit of the quartzite, and it re- 

 calls the remarkable brecciation which has taken place 

 along the fault which forms the northern boundary of 

 the outlier of Enon conglomerate in Baviaan's Kloof. 1 

 The breaking up of the rock along the faults seems to 

 be more than can be accounted for by the friction of 

 the moving masses of rock. The breccia in Baviaan's 

 Kloof and along the Zuurberg fault is probably due to 

 explosions along the fault planes, and in the case of the 

 Zuurberg fissure the explosions brought to the surface 

 great masses of breccias and tuffs, and these were fol- 

 lowed by the rise of basaltic lava. 



As to the date of these eruptions it can only be said 

 that they took place after the Uitenhage beds were de- 

 posited. No trace of superficial outflows of lava or 

 layers of tuff have been found ; the volcanic rocks now 

 form a line of foothills- to the Zuurberg Kange and have 

 been cut down to a surface which is continuous with, 

 and has been produced by the same agencies as, the 

 smooth surface of Zuurberg itself. The occurrence of 

 agates in limestones of Upper Cretaceous age near the 

 Bushman's River has been recorded by Prof. Schwarz, 2 

 and it is possible that they may have been derived from 

 the Zuurberg lavas. 



> See Schwarz, G. C., 1903, p. 132. 



2 In a paper " On the Alexandria Formation," T. G. S. S. A., vol. xi., 

 1908. 



