ANCIENT GLACIAL DEPOSITS 535 



Australia (lat. 30° to 43° S.). (Howchin-14, 15; David-8, 9.) 

 They extend for 460 miles from north to south and 250 miles from 

 east to west, and have a thickness of 1,500 feet. Numerous boul- 

 ders and pebbles showing glacial striae have been obtained (see the 

 figures given by Howchin-15), the character of these boulders in- 

 dicating a soutinvard movement. Intercalated with the tillite are 

 beds of limestone and radiolarian beds. No striations have been 

 found on the underlying rocks. (David-8, 9.) 



In South Africa (lat. 29° S.) tilHte of late pre-Cambric or 

 early Cambric age forms a part of the Griquatown series of Cape 

 Colony, occurring over almost 1,000 square miles. It contains 

 typical scratched boulders. 



TJie Pcniiic Glacial Deposits. These have been observed in 

 India, Australia, South Africa (Davis-io; Schwartz-21), and South 

 America (White-32). The South African deposit constitutes the 

 Dzcyka conglomerate, the lowest member of the Karoo formation 

 (Davis-io '.400). It varies in thickness up to 1,000 feet or more and 

 extends from the Indian Ocean between 29° and 33)^2° south lati- 

 tude northward approximately to Belfast, westward to the Vaal 

 River and thence in latitude 29° to within less than a hundred 

 miles of the Atlantic, and southward to within about 150 miles of 

 Capetown. Its former extent was apparently much greater. "It 

 rests for the most part unconformably on a grooved and striated 

 surface of older rocks, but along its southern border it follows con- 

 formably a series of sandstones and shales. It consists chiefly of 

 an unstratified and consolidated clastic ground mass with sub- 

 angular or rounded scraps, stones, and boulders of many kinds, 

 the finer textured stones and boulders being usually well scratched. 

 It is conformably overlaid by a coal-bearing series of shales and 

 sandstones." ( Davis-io -.400. ) 



"The glacial origin of the Dwyka formation is as unquestionable 

 as is that of the drift sheets of northeastern America or of north- 

 western Europe ; but the Permian ice-sheet, by which the Dwyka 

 was formed, moved in general southward, from the region of the 

 equator toward the region of the pole." (Davis-io:^o/.) The 

 indications are that the Dwyka ice "was a broad and continuous 

 ice sheet which spread across about 600 miles of country, east and 

 west, and which advanced at least 500 miles poleward from its 

 apparent source. It moved across a region which -bore subdued 

 mountains here and there, but which was reduced to moderate relief 

 by previous erosion over large areas." (Davis-io:-^/?.) 



Along its southern margin in latitude 33/^° south it invaded a 

 water-covered area. A number of fluctuations are recorded, and 



