PHYSICAL GEOGRAPHY OF THE CAPE COLONY. 245 



to deserve being treated as a separate subdivision with a distinctive 

 name. 



I think this group is practically the same as the " Olive Shales " 

 of the late Mr. G. AY. Stow *. It would appear from his observa- 

 tions that these shales extend northwards across the Vaal Iliver 

 and abut uneonformably against the old crystalline rocks of the 

 Transvaal, liesting on these old rocks, and forming a basement- 

 bed to the " Olive Shales," is a conglomerate formed out of the 

 underlying rocks, called by Mr. Stow "Ancient Conglomerate " f ; 

 I shall speak of it as the " Basement Conglomerate of the Kimberley 

 Shales." From the description of this bed it seems to me to 

 resemble very closely the Dwyka Conglomerate, and I have my 

 suspicions that it has been confounded with that rock ; but there 

 will be more to be said on this point further on. Mr. Stow also 

 describes conglomerates and sandstones interbedded among the 

 Kimberley Shales on the north. It seems that these are thickest 

 along the line where the Transvaal crystalline rocks rise to the 

 surface and that they thin away rapidly to the south, which 

 indicates that we are here near the edge of the basin in which the 

 Kimberley Shales were deposited. 



Plants are found in the Kimberley Shales, and they occasionally 

 contain lenticular beds or nests of coal. I saw a specimen of one 

 of these found at Kimberley ; it consisted of thin laminae of coal 

 alternating with thin bands of black shale ; the patch from which it 

 was taken, I was told, had been worked all round, and proved to thin 

 away on all sides ; its maximum thickness was six inches, 

 maximum breadth about twenty feet. Even in the hand specimen 

 the laminae of coal were not continuous, but lenticular in shape. I 

 was told also that reptilian bones had been met with in the 

 Kimberley Shales, but I was not able to learn any particulars as to 

 these or the plants. The probability seems to be that the fossils of 

 the Kimberley Shales are similar to those of the Karoo Beds. 



(8.) I have used the term " Karoo Beds " to indicate only a portion 

 of the great group of strata that were originally included under this 

 name. In this limited sense the Karoo Beds consist of alternations 

 of sandstones and shales. 



The sandstones are finely grained, and the majority of them 

 contain a large amount of decomposed felspathic matter, so they 

 incline to be soft. Occasionally more quartzose and harder beds 

 occur ; but it is very rarely, if ever, that we meet with anything 

 approaching the compact quartzite-like sandstones of the Ecca Beds. 

 There is a tendency in the Karoo sandstones to spheroidal weather- 

 ing, but it never reaches the perfection of some of the Ecca sand- 

 stones, and no one would ever run any risk of mistaking a Karoo 

 sandstone for basalt (see p. 244). The weathered outside of the 

 Karoo sandstones is usually of a pale buff colour, but occasionally 

 they are red or purplish. 



The majority of the Karoo clays are shales (but mudstones do 



* Quart. Journ. Geol. Soc. vol. xxx. (1874), p. 610 et seq. t Ibid. 



