CARBONIFEROUS ROCKS OF THE SOUTHERN HEMISPHERE. IL11 
Hemisphere if Glossopteris is to be taken as the upper limit of the 
Permo-Carboniferous. Further, since Glossopteris has such an extended 
range upward it appears unsafe to regard it as a strictly zonal fossil. 
Nomenclature of the Permo-Carboniferous Rocks in South Africa. 
By A. W. Roasrs, D.Sc., F.G.S., 
Director of the Geological Survey of the Union of South Africa. 
In South Africa there is an apparently conformable succession from 
the base of the Cape system, which includes beds with marine fossils 
of Devonian affinities, up to beds at the top of the Karroo system for 
which a Jurassic age has been claimed on account of a crocodile found 
in them. 
This great thickness of rocks has been divided mainly on litho- 
logical grounds, and at the present time it is impossible to point out 
horizons definitely corresponding to the bases of the Carboniferous, 
Permian, and Trias. An attempt to fix such horizons for the purpose 
of applying these widely used terms to South African maps, &c., instead 
of local names would be a mistake. 
The Karroo system is generally understood to include all the strata 
above the Witteberg series up to and including the volcanic beds of the 
Drakensberg. The base of the Karroo system in the south, where there 
is an apparently conformable passage from the Witteberg series, is 
arbitrarily chosen as lying at the top of the highest band of quartzites, 
above which are shales passing into tillite. Further north the base is 
defined by an unconformity which increases in importance northwards. 
The main sub-divisions of the system are as follows: 
Stormberg series. 
Beaufort series. 
Keca series. 
Dwyka series. 
One South African geologist® separates a ‘ Stormberg formation ’ 
from the Karroo, drawing the line at the base of the Molteno beds. 
This suggestion has not been adopted generally because there is not a 
sufficiently marked break at the horizon in question, and certain plant 
species occur both above and below it. There seems to be no need 
to make a separate ‘formation’ of what are conveniently regarded as 
the uppermost strata of the Karroo system. Whether this horizon is 
one which marks an extensive overlap northwards from the Stormberg 
region across thea Orange Free State and the Transvaal remains to be 
proved by mapping; at present the known facts do not favour.that view, 
but important overlaps exist at some horizon within the Ecca or Beau- 
fort series and at another horizon above the Molteno beds. 
The Dwyka Series. 
There is no difficulty in defining this group in the Cape Province 
and Natal and the South-West Protectorate, but in the Transvaal the 
term has not been used in official publications because of the uncertainty 
whether the ‘ glacial conglomerate’ there is really the correlative of 
the Dwyka or whether it was formed at a slightly later time when the 
* Schwarz, S.A. Geology, 1912. 
