Walcot Gibson — Pakeozoic Rocks of South Africa. 165 



in the portion of the Doornbergen examined, but inversion due to 

 overfolding occurs near Prieska Poort. The Matsap Series are 

 found lying in part unconformably on the dolomitic limestone 

 and in part bounded by amygdaloidal lavas. The thickness of these 

 beds is given by Messrs. Rogers and Schwarz,^ as at least 3,000 

 feet, and the top is not seen. 



The Glacial Conglomerate rests unconformably upon all the 

 previous rocks. A description of this remarkable conglomerate 

 has appeared elsewhere,^ and need not be repeated. Stratification 

 is generally absent and the boulders are of local origin ; thus 

 differing in a very marked manner from the Dwyka Conglomerate, 

 with which, however, it seems to occupy a similar position in regard 

 to the beds above, the conglomerate of both regions lying towards 

 the base of the Ecca Series. 



Such is the succession met with round Prieska. It is seen to 

 differ materially from that of the southern provinces. Eocks 

 resembling the Table Mountain Sandstone, Bokkeveld Beds, and 

 Witteberg Series are absent, while the Glacial Conglomerate rests 

 unconformably on a group of strata, of which the representatives 

 may be found among the problematical rocks of the Caugo district, 

 and there only in a very imperfect degree. 



In the south there is a great break between the Table Mountain 

 Sandstone and Malmesbury Beds. Do these Prieska rocks bridge 

 over the gap ? It is interesting to find that the formations round 

 Prieska have had intruded into them igneous rocks of pre-Karroo 

 and post-Karroo ages. In all, Messrs. Eogers and Schwarz have 

 detected five distinct types of igneous rocks, but their complete 

 history has not been made out. 



Considered as a whole, the geological record of the Palseozoio 

 formations of Cape Colony as at present determined is very 

 incomplete. Excepting the sequence from the Table Mountain 

 Sandstone up into the Ecca in the south, the formations are met with 

 only in fragments, and the data necessary to piece them together 

 are wanting or remain to be discovered. It thus happens that the 

 sequence of rocks in the south-east cannot be satisfactorily compared 

 with that in the north-west. 



It is a matter for regret that the relationships of the Cango 

 deposits, Malmesbury schists. Table Mountain sandstones, and of 

 the Prieska rocks, with their igneous history, have not yet been 

 clearly determined. The Prieska rocks strike across the Orange 

 Eiver and are typically developed, judging from Stow's descriptions,* 

 in Griqualand West, and with these the rocks above the famous 

 ' Banket ' formation of the Transvaal Colony have been compared. 



1 Report for 1899, p. 83. 



2 A. W. Eogers & E. H. L. Schwarz : Trans. Soc. Afr. Pkil. See, vol, xi, pt.. 2, 

 pp. 113-120. 



3 Quart. Journ. Geol. Soc, vol. xxx (1874), pp. 581-680. 



