THE GEOLOGICAL HISTORY OF THE COLONY 449 



Towards the end of the Uitenhage period we may 

 suppose that a low belt of land stretched north-east 

 through the middle of the Colony, ending in a great 

 mass of volcanic rocks, and that to the south of this 

 land there were ridges of mountainous ground projecting 

 above a shallow sea, or through gravel and sand de- 

 posited by local streams in a flat country only partially 

 under water. Whether these sediments, in whatever 

 way they were formed, spread north of the Zwartebergen 

 will perhaps never be known, but it is possible that they 

 did so, and that the streams flowing southwards from 

 the main watershed eventually delivered their loads of 

 silt into the same area instead of reaching the open sea 

 to the south-east. It appears to be probable, however, 

 that the rivers ran southwards across the newly de- 

 posited Uitenhage beds when the uplift occurred which 

 put an end to the deposition of those beds in the folded 

 belt. 



These movements followed the strike of the rocks in 

 the folded belt ; their effect was to depress strips of the 

 country between the mountain ranges and thus to ac- 

 centuate the former longitudinal valleys, but though the 

 Uitenhage beds were thus given various dips, usually in 

 a northerly direction, they were not folded in the same 

 manner as the Cape and Karroo formations. 



The extent to which the dislocations were carried 

 was, however, insufficient to disarrange the already 

 established southward courses of the rivers draining 

 the Karroo. These rivers gradually cut down their val- 

 leys through the Uitenhage beds, so that they reached 



the underlying sharply folded Cape formation, a process 



29 



