GEOLOGY OF CAPE COLONY 



C. THE GRIQUA TOWN SEKIES. 



The village of Griqua Town stands at the foot of a 

 long range of hills made of a very remarkable group of 

 rocks the lowest members of the Griqua Town series. 1 



The series is divided into three groups : 

 The Upper Griqua Town beds. 

 The Middle or Ongeluk beds, chiefly of volcanic 



origin. 

 The Lower Griqua Town beds. 



Throughout their range in Cape Colony these beds 

 appear to form a continuous succession, lying conform- 

 ably on the Campbell Hand series, but there may be a 

 slight unconformity between the two lower groups. 



The Lower Griqua Town Beds. 



The characteristic rocks are banded cherts or jaspers, 

 coloured in various shades of yellow, brown and red by 

 hydrated oxides of iron, black by magnetite or blue 

 by the soda-amphibole called crocidolite ; but there are 

 also quartzites, sandstones, grits, shales, limestones and 

 tillite or hardened boulder-clay of glacial origin. All 

 the latter rocks form quite a subordinate part of the 

 group, though some of them are of great interest. 



The Lower Griqua Town beds are occasionally seen 

 to follow the Campbell Kand series conformably, as at 

 Klip Huis and at other places on the same small anti- 



1 After some early descriptions by Burchell and other travellers the first 

 detailed account of these rocks is to be found in Stow, Q. J. G. S., xxx., 

 581, later details in G. C., iv., 80 ; x., 156 ; xi., 31 ; xii., 61, 176 ; andxiii. 

 Also in T, G. S. S. A., ix., 5 ; Rep. S. A. A. A, S. for 1906, 261. 



