﻿682 



ME. E. T. MELLOE ON THH GLACIAL (DWYKA) [Nov. 1905, 



In many cases, however, the outliers have been reduced to patches 



consisting only of the 

 Glacial Conglomerate 

 or its weathered-out 

 remnants, which fre- 

 quently give good op- 

 portunities for study ; 

 while the intervening- 

 areas of older rocks 

 afford information as 

 to the source of much 

 of the material in- 

 corporated in the 

 Glacial Conglomerate, 

 and having been de- 

 nuded comparatively 

 recently of their 

 covering of Karroo 

 rocks, they preserve 

 approximately the 

 character and outline 

 of the land-surface 

 upon which the 

 glacial deposits were 

 laid down. Hound 

 the margins of the 

 Karroo outliers this 

 old land - surface, 

 dating hack as far as 

 Carboniferous time, 

 still preserves aston- 

 ishingly-clear traces 

 of ice-action. 



From the southern 

 and eastern margins 

 of the main area 

 occupied by Karroo 

 rocks in South Africa 

 towards its northern 

 and western edges in 

 the Transvaal, the 

 Karroo System shows 

 a considerable dimi- 

 nution in thickness ; 

 and, while in Cape 

 Colony it attains a 

 thickness of several 

 thousands of feet, in 

 the Central and Northern Transvaal the entire formation probably 



