Walcot Gibson — Palceozoic Rocks of South Africa. 163 



IV. — On the Correlation of thk Paleozoic Kooks of 

 South Africa. 



By Walcot Gibson, B.Sc, F.G.S. 



^IIHE publication of the Annual Reports for 1898 and 1899 of the 

 JL Cape Geological Commission, coupled with the recent account 

 of the geology of the Transvaal Colony by Dr. Molengraaff, and 

 of which a short abstract has appeared in this Magazine/ adds 

 considerably to the knowledge of South African geology. The 

 succession of the rock formations at the Cape has been constantly 

 used as a basis of classification for the rock systems south of the 

 Zambesi. In his recent paper Dr. Molengraaff correlates the 

 formations of the Transvaal Colony with those met with in the 

 south-eastern provinces of Cape Colony, and emphasizes the fact 

 that the three stages of the Pretoria, Dolomite, and Black Eeef 

 series of the Transvaal Colony may be compared with the 

 Witteberg, Bokkeveld, and Table Mountain Sandstone series of 

 the Cape. It may therefore be of service to show on what 

 grounds this supposed correlation is based. To do this the 

 succession at the Cape of the formations below the Beaufort Beds 

 in the typical region of the south-eastern province will first be 

 given. The grouping adopted by the Cape Geological Commission ^ 

 is in descending order of sequence as follows :-^ 



Table of Strata below the Beaufort Beds of Cape Colony. 



Eoca Beds ... ... ... Sandstones and shales with G^««(/«;Moj;fcris. 



Bwyka Series ... ... Congiomerates and interbedded plant - bearing 



shales. Included boulders of distant origin. 

 Witteberg Beds ... ... Mainly quartzites. Spirophyton. 



Bokkeveld Beds Shales, sandstones, and greywackes. Fossils of 



a Devonian facies. 

 Table Mountain Sandstone Sandstones and quartzites with occasional shales. 



Great Unconformity. 

 Jllalmesbury Beds Non - f ossiliferoUs slates, phyllites, mica - schists, 



and quartzites. Granite, quartz-porphyry, and 



diabase as intrusive rocks. 



From the Table Mountain Sandstone upwards there is no break 

 in the succession of these deposits, which are several thousand feet 

 thick and have been traced successively along a length of outcrop 

 extending for over 100 miles ; on the other hand, the hiatus between 

 the Table Mountain Sandstone and Malmesbury Beds is unequivocal. 



The whole series, excepting on Table Mountain and near the 

 coast, are thrown into complex folds, admirably displayed in the 

 Hex River Mountains and Klein Zwartebergen. Instances of 

 complete inversion are not infrequent, and are particularly apparent 

 north of the Zwartebergen. It is to the south of this range, in the 

 Cango distx'ict, that some deposits of slates, dolomitic limestones, 

 and sheared conglomerates and grits are met with overlying the 

 Table Mountain Sandstone, but brought into this position by 



1 Geol. Mag., Dec. IV, Vol. VIII (1901), pp. 475-8. 



2 Reports, 1897 et seq. 



