Glacial Beds. 263 



of some 115 miles from south to north. The width of the area is 

 about 30 miles. It has not yet been found west of the Langeberg or 

 east of the Kaap Plateau. In all cases it is succeeded by the Ongeluk 

 volcanic series within about 30 feet. In the Good Hope outlier 

 there are less than 12 feet of thin, bedded, dark quartzitic rock 

 between the two, and the same is the case at Monjana Mabedi and 

 Punt. At Juanana the intervening beds may be 30 feet thick. 

 Generally there is a tract of low ground between the nearest outcrops 

 of the Griqua Town and Ongeluk series, and it is only where hills 

 made of the latter series rise sharply from the underlying beds that 

 the succession has been clearly seen. The glacial beds have been 

 found to underlie the Ongeluk series over a very wide area, and in 

 nearly every outlier of the latter, the only exception being the Paarde 

 Vley syncline, which has not been re-examined since the existence of 

 the glacial beds was discovered, and there can be little doubt that 

 the succession is a conformable one. 



The source whence the chert and other rocks forming boulders in 

 the glacial beds came is still unknown. The frequence of chert 

 nodules should prove to be of material help in settling the question, 

 but at present such nodules have not been described from South 

 African rocks. The only similar nodule known to me from any other 

 rock was shown me by Mr. D. J. Haarhoff, M.L.A., in Kimberley 

 in April, 1906, and he says it came from the " blue-ground " of the 

 Kimberley INIine. This nodule is so like those mentioned above that 

 I am inclined to believe that they all came from the same formation. 

 The mode of occurrence of the chert in the Campbell Rand beds is 

 not like that indicated by the form of the chert nodules in the glacial 

 beds. 



As to the age of the Griqua Town beds, there is nothing new 

 to say. All recent writers on the subject are agreed that these beds 

 are older than the Cape System of the south, but there is a difference 

 of opinion as to the probable lapse of time between them. If, with 

 Passarge (i) and Hatch and Corstorphine (2), we regard the uncon- 

 formably overlying Matsap beds as the equivalents of the Table 

 Mountain series of Lower Devonian or Silurian age, the Griqua Town 

 beds may not be very much older than those periods. We know 

 that after the deposition of the Griqua Town beds there took place 

 a great outpouring of volcanic rocks in Cape Colony, and that both 

 the volcanic rocks and the underlying sedimentaries were subjected 

 to earth movements and prolonged denudation before the Matsap beds 

 were laid down. This correlation of the latter with the Table Moun- 

 tain series is, however, of doubtful value. It is based chiefly on two 

 facts ; first, a certain degree of lithological resemblance, and, second, 

 the fact that both are older than the Dwyka series, and rest uncon- 

 formably upon still older rocks. 



As to the lithological resemblance, when we have stated that both 

 groups are largely made of quartzites, with occasional thin bands of 

 pebbles and isolated pebbles, we come to the end of the similarity. 



(I) Die Kalahari, 1904. (2) The Geology of South Africa, 1905. 



