INTRODUCTION 11 



In the Langberg-Korannaberg range the beds are in 

 places overfolded and dip towards the west. West of 

 the Langberg there are parallel ranges of the same 

 rocks (Matsap series) and also of the very much older 

 Kheis beds; these hills project from the Kalahari sand, 

 but the Dwyka formation, lying flat, is met with at several 

 places in wells or on the surface in Gordonia, and it is 

 extremely probable that a very large area of the sand- 

 veld is underlain by a thin layer of the Dwyka. This 

 circumstance bears out the conclusion drawn from the 

 study of Prieska, Griqualand West and Bechuanaland, 

 that all the main surface features of those areas, ex- 

 cepting the valley of the Orange Eiver, were in existence 

 during Dwyka times and have been again exposed by the 

 removal of the Dwyka series and higher members of the 

 Karroo system. 



The Karroo formation rests apparently undisturbed 

 on all these ancient rocks of the north, and there is 

 much evidence that the main source of the rock debris 

 forming the Southern Dwyka was in the north. The 

 base of the Dwyka, however, falls southwards as the 

 valley of the Orange Eiver is approached, and again 

 rises to higher levels south of the river before it dips 

 down under the great area made of Karroo sediments in 

 the central portion of Cape Colony. Whether this fall 

 towards the Orange Eiver is due to a slight synclinal 

 fold, or whether it indicates the presence of a valley or 

 a series of depressions along the course of what is now 

 the Orange Eiver, is still uncertain, but the known facts 

 seem to favour the former conclusion. 



