432 PRE-DWYKA DENUDATION 



It is clear that in the country immediately north of 

 Karroo Poort, where the only beds usually met with in 

 the southern districts that are missing are the Lower 

 Dwyka shales, the exposure of the Witteberg series 

 must have been of very short duration. Farther north 

 their exposure to the agencies of denudation began at 

 an earlier time, so that more and more of the Witteberg 

 and Bokkeveld rocks were washed away before the 

 Dwyka conglomerate was laid down upon the remnants. 

 It is obvious that deposition and denudation on a large 

 scale cannot go on at the same time in one and the 

 same district, so that at Matjes Fontein on the Oorlog's 

 Kloof River, where only the lowest of the Bokkeveld 

 beds remain between the Dwyka conglomerate and the 

 Table Mountain sandstone, and where some 2,000 feet 

 of the Bokkeveld beds, if the series was ever so com- 

 plete there as farther south, are missing, the removal of 

 the rest of the group must have taken place during the 

 formation of the Witteberg beds in the south. We can 

 be certain, therefore, that the Witteberg beds were 

 never deposited in the area just north of Matjes Fontein 

 (Oorlog's Kloof Kiver). 



The northward extending depression, which allowed 

 first the Table Mountain sandstone and then the marine 

 beds of the Bokkeveld series to be deposited north of the 

 thirty-third parallel, gave way to the opposite movement 

 of upheaval at some time during the deposition of the 

 upper part of the Bokkeveld or lower part of the Witte- 

 berg group. 



It is possible that this change of direction in the 

 vertical movement of the land was coincident with the 



