E. T. Jfellor — Glacial Conglomerate of South Africa. Ill 



account for the peculiar characters of the conglomerate. A. G. 

 Bain, " The Father of South African Geology," who first 

 described the Dwyka Conglomerate in 1856, suggested that it 

 represented a flow from an immense volcano. Prof. A. H. 

 Green thought it to be a " coarse shingle formed along a reced- 

 ing coast-line," while from Green's specimens Sir A. Geikie 

 and Dr. F. fl. Hatch considered it had the aspect of a volcanic 

 breccia. The majority of South African geologists favored 

 the igneous theory, accounting for its peculiar characters and 

 occasional stratification by referring its origin to submarine 

 volcanoes. 



A glacial origin was first attributed to the conglomerate in 

 1868 in a paper on the Geology of Natal by Dr. P. C Suther- 

 land,* who had previously regarded the rock as a lava-flow. 

 Sutherland, who was familiar with the conglomerate in Natal, 

 where the rock has more the features of a terrestrial glacial 

 deposit, and rests in places upon striated rock surfaces 1 clearly 

 stated the real character of the rock. The glacial view 

 received early support from Stow,f who, however, referred 

 the glaciation to a much later period, and subsequently from 

 Schenck.J Dunn, who did so much to work out the main fea- 

 tures of the distribution of the Glacial Conglomerate as shown 

 in the various editions of his " Geological Sketch Map of 

 South Africa," regarded the rock as largely due to the action 

 of floating ice, an agent which no doubt had much to do 

 with the southern deposits. 



It is only quite recently, however, that owing to the accumu- 

 lation of evidence§ from various localities in South Africa the 

 glacial origin of the Dwyka Conglomerate has received anything 

 approaching general acceptance. 



Recent Studies of the Glacial Conglomerate. — Jn 1898 Dr. 

 Molengraaff[ published a description of the Dwyka Conglom- 

 erate, and overlying Ecca beds, as developed in the Yryheid 

 district of the Transvaal, to the north of the Natal border (now 

 included in the latter colony). In the Yryheid- district the 

 Dwvka Conglomerate averages about 300 feet in thickness, and 

 lies un conform ably upon an old land surface composed mainly 

 of the hard quartzites and shales of the Barberton formation — 

 the surfaces of which are frequently polished and striated. 

 Both the conglomerate and succeeding Ecca Shales offer good 



* P. C. Sutherland, On the Geology of Natal, Pietermaritzburg, 1868. 



+ G. W. Stow, On some Points in S. A. Geology, Q. J. G. S., vol. xxvii, 

 pp. 497-548. London, 1871. 



% A. Schenck, Die Geologische Entwickehing Siidafrikas, Pet. Mitt., Band 

 xxxiv. Gotha, 1888. 



§ See recent reports of the Geological Surveys of Cape Colony, Natal and 

 the Transvaal. 



|| G. A. F, Molengraaff, The Glacial Origin of the Dwyka Conglomerate, 

 Trans. Geol. Soc. S. A., vol. iv, 1898. 



