260 ABSENCE IN THE FOLDED BELT 



tion of the Ecca beds. The position of their approxi- 

 mate southern limit is shown in the large coloured map. 



In the west of the Ceres Karroo a nearly straight 

 dyke about thirteen miles long and 100 feet wide runs 

 north and south through Beukes Fontein, traversing the 

 Dwyka conglomerate where that formation dips some- 

 what steeply to the east. This dyke dies out at each 

 end and gives off no sheets. In the valley of the 

 Brandewyn's Kiver there are two dykes traversing the 

 Bokkeveld and Table Mountain series in an area where 

 these beds are slightly folded, and in the neighbourhood 

 of Groen Kiver and the Bokkeveld Mountain escarpment 

 there are also two dykes breaking through beds belong- 

 ing to the Cape system, but the beds have there been 

 only very slightly disturbed. 



No dolerite intrusions have been met with in the 

 great folded belt between the Clanwilliam Mountains 

 and the Gualana Kiver. We have to go to the Cape 

 Peninsula and to Pondoland, where the Table Mountain 

 series lies almost horizontally, before we again come 

 across dolerite in the Cape system. These occurrences 

 are in the form of narrow dykes in the Peninsula and a 

 thick sheet in Pondolaud. 



The northern limit of the Karroo dolerites is not yet 

 known, for rocks of this type have been found as far 

 north at least as Mafeking and near Kietfontein on the 

 German border. 



It is important to note that sheets are abundant in 

 the Karroo system, but that wherever the latter have 

 been removed by denudation, the intrusions in the Pre- 

 Karroo rocks almost invariably form narrow dykes. 



