900 REVIEWS 



near Baie des Peres. That they extend still further to the east, is shown by 

 Low's report on Labrador, where conglomerates with Laurentian bowlders 

 and jasper bowlders and pebbles seem to be common. 



It is not certain, of course, that every one of these rocks containing 

 pebbles of jasper, chert, or sandstone is a basal conglomerate of the Upper 

 Huronian, but many of them undoubtedly are, and in the majority of cases 

 the source of their pebbles is found in adjoining bands of siliceous iron-bear- 

 ing rocks which maybe looked on as belonging to a horizon near the top of 

 the Lower Huronian, Van Hise's Mareniscan. 



Willmott 1 describes the geology of the Michipicoten area 

 northeast of Lake Superior. He makes the succession from the 

 base up as follows : 



i. Lower Huronian green schists. Some of these are 

 undoubted lava flows showing the characteristic elliptical struc- 

 ture described by Clements as occurring in the Hemlock forma- 

 tion of the Crystal Falls district. At a number of points 

 agglomerates are found, as at Little Gros Cap fish station, north 

 of Goetz Lake, east of Manitowoc, and elsewhere. Commoner 

 occurrences are the various green schists, chlorite, hornblende, 

 mica, and sericite schists. Presumably all these schists are 

 derived from lavas, basic and acidic. The dip of the schists is 

 always nearly vertical and the strike follows closely the line of 

 contact with the granite, to be described later. 



2. Lower Huronian sediments. The most characteristic of 

 these is a belt of ferruginous chert, which has been found at 

 intervals for about sixty miles. This rock consists of banded 

 hematite and silica with usually some residual carbonate of iron. 

 The bands vary from one-tenth of an inch in thickness up to 

 several inches. The silica is sometimes very like loaf sugar ; 

 again it is like quartzite, chert, or jasper. Red jasper is not 

 infrequent. The hill at the back of the Helen mine is a huge 

 mass of siliceous carbonates. The rocks, as a whole, and the 

 mode of occurrence of the ore, are strikingly like the Lower 

 Huronian iron formations of Marquette and Tower. Besides the 

 iron formation, beds of carbonaceous shales and limestones have 

 been recognized at several points. Shale occurs interstratified 



'"The Michipicoten Huronian Area," bv A. B. Willmott, American Geologist, 

 Vol. XXVIII, 1901, pp. 14-19. 



