

450 W. M. DAVIS OBSERVATIONS IN SOUTH AFRICA 



Plate 58. — Dicyka Tillite and glaciated Barberton Slates 



Figuke 1.— Contact of Dwyka tillite, left foreground, against a glaciated sur- 

 face of Barberton slates. 

 This exposure is in a ravine north of Ngotsche, Vryheit, looking 

 northwest. The inclination of the surface of contact is an 

 original feature, not due to subsequent tilting. The glacial 

 striations on the slates descend to the left ; they are faintly 

 seen because the sunshine came in the same direction. Penck 

 is standing on the upper ledge and Molengraaff to the right 

 below (see page 407). 



Figure 2. — A glaciated surface of Barberton slates overlaid by Dwyka tillite. 



This exposure is in a ravine north of Ngotsche, Vryheit, looking 

 north. Penck stands on the Dwyka tillite, Molengraaff stands 

 across the contact, and Hobson is on the Barberton slates ( see 

 page 407). 



Plate 54. — Glaciated Diabase 



Figure 1. — Deeply furrowed glaciated surface of diabase. 



The Dwyka tillite has recently been stripped from the diabase. 

 The view is on the Vaal river, near Riverton, 16 miles north 

 of Kimberley, looking east-northeast. The ice-movement was 

 toward the foreground. Some of the tillite remains in the 

 right-hand furrow. From a photograph by Professor R. B. 

 Young, of Johannesburg (see page 412). 



Figure 2. — Glaciated surface of diabase. 



The picture is from the same locality as the preceding view. 

 The ice-movement was toward the background. A patch of 

 tillite remains on the diabase at the farther end of the ledge. 

 From a photograph by Professor R. B. Young, of Johannes- 

 burg (see page 412), 



