THE LOWER HURONIAN ICE AGE 



A. P. COLEMAN 



INTRODUCTION 



When geologists slowly became convinced of the reality of the 

 Pleistocene glacial period it was held to be a unique catastrophe 

 belonging to the later history of a cooling world, something without 

 precerlent in earlier geological epochs. Then, reluctantly and with 

 astonishment, a Permo- Carboniferous glacial period, even more tre- 

 mendous than that of the Pleistocene, was admitted as proved. Later 

 still, an extensive ice age in early Cambrian or late pre-Cambrian 

 times has been demonstrated, carrying back continental glaciers to 

 the beginning of known life in the world. 



For a number of years it has been my belief that a still earlier glacial 

 period was the cause of the widespread basal conglomerate of the 

 Lower Huronian; and last year, when a few scratched stones were 

 obtained from this conglomerate at the silver-mining region of Cobalt, 

 it seemed worth while to show that a Lower Huronian ice age was 

 highly probable.^ 



During the past summer fresh material has been collected in the 

 Cobalt region, including some well-preserved "soled" bowlders with 

 ice-smoothed surfaces and well-marked striae, removing all doubt of 

 the glacial origin of the conglomerate; and it is proposed to present 

 here the evidence for this most ancient of known ice ages. 



THE STONES OF THE BOWLDER CLAY 



It requires patience to separate the pebbles and bowlders from the 

 hard matrix of the conglomerate, or tillite, to use Pcnck's term, and 

 no very large number have been extracted, but most of them have the 

 characteristic subangular forms of glaciated stones. As illustrations, 

 two photographs are reproduced, the largest stone represented being 

 about eight inches across, and having good striae on both sides and 

 in more than one direction, one set crossing another. If the speci- 



I American Journal of Science, Vol. XXIII, March, 1907. 



149 



