A. P. Colemmi — Lower Huronian Lee Age. 189 



graywacke or slate, though sometimes it is schistose or looks 

 like an eruptive rock. 



The pebbles or bowlders are in many cases subangular or 

 sharply angular and are found miles away from any known 

 source ; and as they may be of any size up to blocks weighing 

 tons, and are frequently very sparsely scattered through an 

 unstratified matrix, a stone or two in several yards, one cannot 

 help suspecting that the transporting agency was ice rather 

 than water. There are parts of the formation where the 

 pebbles or stones are well rounded and crowded in certain 

 bands. In such cases they are probably true water-formed 

 conglomerates; but the prevalent type of the rock with scat- 

 tered subangular stones or bowlders should not be called a 

 conglomerate, any more than a Pleistocene bowlder clay would 

 receive that name. The appearance of these so-called slate or 

 graywacke conglomerates is closely like that of the Dwyka 

 bowlder clays, for which Penck suggests the term " tillite." 



Good examples of these bowlder-bearing rocks are found in 

 the original Huronian region on Echo lake, near Desbarats 

 and on the Palladeau Islands. At the last locality smooth 

 water-worn surfaces give excellent sections of the rock, the 

 scattered red granitic bowlders standing out sharply from the 

 dark greenish gray matrix. The granite bowlders similarly 

 enclosed near Desbarats are twenty miles from the nearest 

 known outcrop of that rock. 



Logan describes a similar " slate conglomerate" from Lake 

 Temiscaming, and also a schist conglomerate from Dore river 

 on Lake Superior as belonging to the same formation ; and in 

 some cases his measurements made them hundreds or even 

 thousands of feet thick.* 



Later explorations in northern Ontario, described in reports 

 of the Bureau of Mines of the province, have brought to light 

 many other areas of the so-called conglomerate, some very 

 characteristic ones occurring near Sudbury and east of Lake 

 Wahnapitae ; while schistose varieties, which have undergone 

 more severe squeezing and metamorphism, occur near Shoal 

 Lake, Manitou Lake and on the Lake-of-the-Woods. In fact, 

 rocks of the kind are found from point to point across all 

 northern Ontario, a distance of nearly 800 miles, and from 

 the north shore of Lake Huron in latitude 46° to Lake Nipi- 

 gon in latitude 50°. 



The more schistose of these conglomerates have their peb- 

 bles flattened and rolled out into lenses not at all suggesting 

 glacial action ; but the fact that all of them, whether schistose 

 or unmodified, occupy, so far as known, the same position, 

 immediately over the Keewatin, and contain pebbles and 



*G. S. C, 1863, p. 56. 



