LOWER HURONIAN GLACIAL PERIOD 355 



In the Australian reports previoiisl}' referred to, Professor David men- 

 tions that rocks of a similar character to the Cambrian tillites, and prob- 

 ably of the same age, occur on Mackenzie river, in Canada, and on the 

 Lena, in Siberia, but I have not been able to find descriptions of these 

 boulder conglomerates. 



If the glacial beds referred to above were all formed in the same age, 

 which seems probable, the early Cambrian glaciation extended to both 

 hemispheres in latitudes from 29° to 70°, and, at least in Australia, 

 covered thousands of square miles and reached sealevel in regions now 

 having a warm temperate climate. It is interesting to note that the 

 Cambrian ice age, like that of the Permo-Carboniferous, seems to have 

 been most intense in the southern hemisphere, in Australia and South 

 Africa. 



The Lower Huronian Glacial Period 



Probably the earliest suggestion of a Huronian ice age was made by 

 Shaler and Davis in their work on Glaciers, where the origin of some of 

 the conglomerates is described as probably glacial.^^ 



Sir Archibald Geikie states of certain Archean boulder beds in Scotland 

 that "where the component blocks are large and angular, as at Gairlock, 

 they remind the observer of the stones in a moraine or in boulder clay."** 



The first recorded striated stones of Huronian age have been found 

 within the past two years in the Cobalt silver mining region of Ontario 

 by the present writer, the earliest account of the Lower Huronian tillite 

 having been published in the American Journal of Science for last year.''' 

 A much fuller treatment of the subject, with photographs of tillite, stri- 

 ated stones, etcetera, has appeared in the Journal of Geology, and for 

 details the reader may be referred to that article.'* With the exception 

 that no striated rock surfaces have yet been found beneath the Lower 

 Huronian tillite, all the varieties of evidence depended on to prove the 

 glacial origin of the Permo-Carboniferous apply perfectly to this most 

 ancient glacial deposit. Specimens of the boulder clay from the two 

 horizons are almost indistinguishable in hand specimens or in thin sec- 

 tions under the microscope. 



How suggestive these boulder conglomerates are of glacial work is 

 shown in accounts prepared by geologists who hesitate to draw the same 



33 Glaciers, p. 101. 



=* Text-book of Geology, p. 705. 



^ American Journal of Science, vol. xxiii, 1907, pp. 188-192. 



^ Vol. xvi, pp. 149-158. 



