BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 11, pp. 107-114 March 20, 1900 



UPPER AND LOWER HURONIAN IN ONTARIO 



BY ARTHUR P. COLEMAN 



{Read before the Society December 28, 1899) 

 CONTENTS 



Page 



Introduction 107 



Ferriferous sandstones, cherts, and jaspers , 107 



Extent of the Iron range , 108 



The Dore conglomerate 109 



Conglomerates near Rainy lake , 110 



The jaspers of the eastern Huronian Ill 



Source of jasper pebbles of the Huronian 112 



The most important break in the Huronian 112 



Conclusions 114 



Introduction 



The original Huronian area, as mapped by Logan and his assistant, 

 Murray, lies within the province of Ontario, which contains also its north- 

 eastern extension toward lake Temiscaming and several other large and 

 important tracts which have been mapped with more or less certainty 

 as Huronian by Canadian geologists since Logan's time. As these rocks 

 contain the most promising ore deposits of the province, they naturally 

 attract much attention from prospectors and geologists, and the problems 

 connected with their formation and relationships have an economic as 

 well as a purely scientific interest. The question as to what areas are 

 really Huronian, and as to the relative age of the different areas mapped 

 as Huronian, differing as they often do in striking ways from the rocks of 

 the original region, is one requiring solution if the pre-Cambrian geology 

 of the province is to be placed on an assured basis. During the past 

 summer an examination of the newly discovered iron region in the Hu- 

 ronian district northeast of lake Superior for the Bureau of Mines of 

 Ontario has provided a set of facts which appear to throw new light on 

 the subject. 



Ferriferous Sandstones, Cherts, and Jaspers 



For a number of years iron ore has been known to exist at little Gros 

 Cap, on Michipicoton bay, but the finding of important deposits of high- 



XV— Bum,. Geol. Soc. Am., Vol. 11, 1899 (107) 



