260 PEOF. A. H. GEEEN ON THE GEOLOGr AND 



We now pass to the great saucer-shaped basin of Kimberley Shales, 

 Karoo Beds, and l^Iolteno Beds which occupies the northern part of 

 the country under description. 



These three formations are conformable to one another, and are 

 separated from the underlying Ecca Beds by a most marked uncon- 

 formity. J^[othing perhaps arrests the attention of the geologist 

 who is traversing the countrj^ for the first time more forcibly than 

 this unconformity. As you move leisurely along over many of the 

 tracts of Ecca Beds, you feel that the ground over which you are 

 driving is neither more nor less than a great geological map. The 

 state of the roads is not such as to promote easy travelling, but 

 is admirably calculated to reveal the geological structure of the 

 country. A rude jolt tells you that you have driven over the outcrop 

 of a hard bed which stands up in a little reef across the road, and 

 a glance over the side of the cart tells you which way the bed is 

 dipping. You may be tired and a little remiss, but these reminders 

 come too often to allow of your neglecting your geology ; you note 

 that the strike is steadily east and west, that the dip is now to the 

 north, now to the south, now steep, now gentle ; and so you realize 

 that the beds you are crossing lie in a long succession of folds. Prom 

 time to time you cast j^our eyes towards a long line of bold hills 

 which bounds on the north the plain you are traversing, and 

 stretches away both to the east and west as far as the eye can follow 

 it. The long level stripes which bar the slopes of these hills plainly 

 show that the rocks composing them are horizontal ; and, though 

 you may be miles away from the junction, you have a conviction 

 that these rocks must rest unconformably on the folded beds of the 

 plain. ISTo one accustomed to read great physical features can fail 

 to come to this conclusion. Later on you come to know that these 

 hills are formed of Karoo Beds. 



I saw the actual junction of the Karoo and Ecca Beds only on 

 the farm of Mr. E-abies, about a two hours' drive to the north of 

 Aberdeen. There could be no question here about the unconformity. 

 The section which showed it most distinctly is given in fig. 3. 



The hills just mentioned are a part of that long strip of elevated 

 ground which runs right across the country and forms the southern 

 boundary of that northern tract of undisturbed rocks of which we 

 are now treating. It is one of the most conspicuous of the physical 

 features of South Africa, with an aspect everywhere most marked 

 and everywhere the same. Plenty of panoramic views may be ob- 

 tained from the higher points, and they all show a country traversed 

 by interrupted ranges, trending generally east and west, and dotted 

 over with isolated eminences. The hills are formed of Karoo Beds, 

 and show the horizontal striping already described as so charac- 

 teristic of that formation. Here and there a hill-range is crowned 

 by an escarpment of unusual height and boldness, formed by one 

 of the great intrusive trap sheets, or an isolated hill has a capping 

 of trap, which makes it a landmark for miles round. Trap sheets 

 project elsewhere along the slopes of the hills, readily distinguish- 

 able by their ruggedness from the narrow bars that mark the out- 



