A. P. Coleman — Lower Huron ian Ice Age. 187 



Art. XVII. — A Lower Huronian Ice Age ; by A. P. Cole- 

 man. 



Of late years the evidence for ice ages far older than the famil- 

 iar Pleistocene Glacial Period has been growing rapidly, and 

 at least one Paleozoic ice age, that of the Permian or Permo- 

 •Carboniferous of India, Australia and South Africa, must be 

 looked on as fully established. All the geologists who visited 

 South Africa with the British Association in 1905 were con- 

 vinced of the glacial origin of the Dwyka " tillite," or bowlder 

 clay, and of the striated rock surfaces beneath, found from 

 point to point for 600 miles. The evidence for the equivalent 

 glacial beds of Australia and India appears to be equally clear, 

 as shown by Professor David of Sydney University at the late 

 meeting of the Geological Congress in Mexico. 



This well established ice age of Paleozoic times makes it 

 far more probable that glacial periods are a normal, if infre- 

 quent, feature of the world's past history ; and adds weight 

 to the evidence so far recorded of very ancient ice ages, such 

 as those of the Cambrian. 



It will be recalled that what is probably an early Cambrian 

 glacial deposit was described by Peusch in the Gaisa beds of 

 northern Norway in 1891 ;* and reexamined by Strahan in 

 1897. The region in which these comparatively small out- 

 crops of bowlder clay were found is, however, in latitude 70°, 

 so that Arctic conditions of a local kind might not be surpris- 

 e- 

 More recently Bailey Willis has described before the Geo- 

 logical Society of America an early Cambrian or possibly Pre- 

 cambrian Glacial formation on the Yang-tse river in China, 

 in latitude 30°. The specimens of striated stones which he 

 displayed were characteristic, and the matrix suggested an 

 ancient bowlder clay.f 



In 1905 A. W. Rogers of the Cape Colony Survey described 

 a glacial conglomerate in the Table Mountain series.- This 

 had been discovered four years before, but was now worked 

 out more in detail and found to extend at least 23 miles. It 

 contains stones of typically glacial appearance. The age of 

 these rocks seems not quite certain, since no fossils have been 

 found in the Table Mountain series, but they are very early 



* Norges geologiska Undersogelse ; Det nordlige Norges Geologi, pp. 26-84, 

 1891. Geol. Soc. London, vol. liii, pp. 137-146, 1897.' Mr. Strahan's paper 

 is accompanied by plates showing the bowlder clay and the striated rock sur- 

 face beneath it. 



f Year Book No. 3, Carnegie Inst., p. 282 ; see also Chamberlin and Salis- 

 bury's Geology, II vol. , pp. 273-4, where photo reproductions of glaciated 

 pebbles are given. 



