THE GEOLOGICAL HISTORY OF THE COLONY 445 



Uitenhage age the limit will be correspondingly set 

 back. But the first argument, concerning the connec- 

 tion of the dolerites and volcanic beds, certainly sup- 

 ports the assumption that the intrusions took place 

 at the close of the Stormberg period, and this helps us 

 to determine the date of the folding in the southern 

 mountainous region. 



Whether closer limits can be set to the period of fold- 

 ing than the Ecca and Uitenhage periods remains to be 

 found out in the future. It is possible that the uncon- 

 formity near Aberdeen, between the Ecca and Beaufort 

 beds, described by the late Prof. A. H. Green, may 

 be more than a local phenomenon, and if so it may 

 lend material aid to the solution of the question, but so 

 far as our knowledge of other parts of the Colony goes 

 there is no physical break at that horizon. It may be 

 that all traces of the unconformity which probably 

 existed within the Karroo formation somewhere to the 

 south of the main Colonial watershed have been re- 

 moved by denudation. The uprising of the folded belt 

 exposed the southern parts of the Colony to the air and 

 to all the destructive agencies, such as change of tem- 

 perature, wind, rain and streams, that this entajled. 

 There were then formed the great longitudinal depres- 

 sions between the Zwartebergen and Langebergen and 

 the other more or less east and west ranges in the 

 south. To this period probably belongs also the first 

 rough shaping of the western coastal districts, the 

 removal of the upper parts of the Cape formation from 

 Malmesbury, Piquetberg and neighbouring districts, and 

 the Olif ant's River Valley (Clanwilliam). While this 



