On soufH African strata. 141 



Report by Dr. A. W. Eogers. 



1 tliink the result of the discussion is chiefly of value in showing 

 how we stand in these matters, though I am very sorry that all the 

 trouble you have taken has not produced the unanimity you would like; 



I think you are inclined to overestimate the present value of our 

 knowledge of South African geology. One great defect is the want of 

 information as to the relative ages of the large granite intrusions. If 

 we could say with certainty that the Cape Town, Namaqualand, Gor- 

 donia, Bechuanaland, and Transvaal (old) granites were of one age, 

 I would gladly agree to the term Swaziland System for all older 

 sedimentaries ; but this is not the case, and the N.W. Cape area i3 

 too little known to allow the matter to be fairly discussed. In ten 

 years' time, perhaps, we shall be better off. 



Both du Toit and I are at the present moment much exercised — 

 both in leg and mind — on this granite question. We do not agree on all 

 points, but that is not from any motive but a desire to get to the 

 bottom of it. I do not like to throw whatever weight my decision would 

 carry into one scale at present. 



I think Schwarz's scruples about the Vaal or Ventersdorp System 

 well founded. I think I made a similar sort of remark in Annual 

 Report for 1906, but cannot refer you to the page, as I am in camp in 

 Prieska district. It comes in the section on the Pneil series in a report 

 on Vryberg and Kuruman. 



The connections between the Vaal and Transvaal ' systems ' is very 

 close, and the unconformities are not limited to the break between the 

 two systems. 



Supplementary Report by Dr. Hatch. 



Since I wrote the above notes I have spent the best part of a year 

 in Natal, and have had an opportunity of studying the ancient floor of 

 crystalline schists and intrusive granites which there emerges from 

 below the horizontally bedded Karroo and Table Mountain Sandstone 

 formation, and is admirably exposed in the deeply incised valleys of 

 Zululand. The schistose rocks, which are largely of sedimentary 

 origin, are of great variety — dark-coloured hornblende-schists much 

 permeated with aplite and pegmatites, and frequently cut by intrusions 

 of serpentine, occur in the Mpapala, Fort Yolland, and Lower Tugela 

 River districts; mica-schists and kyanite-schists, in the Nkandhla 

 Forest and on the Bobe Bidge; micaceous and chloritic schists, in the 

 Mfongosi Valley ; conglomerates, quartzites, quax'tz-felspar-schists, and 

 sericite-schists, in the Buffalo River and Insuzi Valleys; and magnetite- 

 quartz-schists, jasper-schists, and quartzites, in the Vryheid district. 



There is no lithological succession that at all resembles the typical 

 Rand section, and I do not think that representatives of the Witwaters- 

 rand System exist in Natal. Nor do I agree with Voit 1 that the horn- 

 blende-schists, with their permeation veins of aplite and pegmatite, 

 can be directly correlated with the Lewisian or Laurentian gneiss. 



"With regard to the red sandstone and conglomerate formation, 



1 Trans. Oeol. Soc. S.A., vol. x. (1907) pp. 93 94. 

 1910 L 



