REVIEWS 901 



with the ferruginous chert at Iron Lake. Near Paint Creek and 

 at Eleanor Lake it has also been found. Whether it always 

 underlies the iron formation is undetermined, but it probably 

 does not. The cherty limestone has been traced in a fairly con- 

 tinuous line from the Helen mine to the east of Park's Lake, a 

 distance of twelve miles. 



3. Upper Huronian sediments. These consist of schist-con- 

 glomerate. Coleman describes the bowlders as "granites most 

 frequently, then quartzites, or sandstones with pebbles generally 

 small, next green schists, then felsite schists and porphyroids, 

 and finally a few gneisses, but none of the Laurentian type." A 

 thin section of one of the quartzite pebbles showed considerable 

 carbonate, proving that it undoubtedly came from the iron 

 formation. This conglomerate has been traced pretty contin- 

 uously for thirty-eight miles in a semicircular belt around the cen- 

 tral granite boss. At many points, as at Iron Lake, Dog River, 

 Dore River, Wawa Lake, it contains pebbles from the very char- 

 acteristic iron formation. This fixes its age as Upper Huronian. 



4. Laurentian granite, intrusive in the Huronian rock. The 

 granite is in undoubted eruptive relations with the conglomerate 

 along the shore of Superior, for example a few miles west of 

 the Dore. A mile and a half up the Magpie, a boss of granite is in 

 eruptive contact with the conglomerate, and although it may not 

 be of the same age as the larger boss three miles to the north- 

 west, it probably is. In the opposite direction a succession of 

 granite gneiss bosses intrusive in the schists are found, for six 

 miles, after which the granitoid gneiss occurs without interrup- 

 tion for over a hundred miles. 



Comment. — Van Hise 1 has referred Willmott's " Lower Huron- 

 ian" green schist and iron-bearing formation to the Archean, 

 and has referred his "Upper Huronian" schist-conglomerate 

 series to the Lower Huronian. Indeed he would so refer most 

 of the conglomerates described as Upper Huronian by Coleman 

 in the article above summarized. The Michipicoten series show 

 close similarities in structure and lithology to portions of the 

 Archean and Lower Huronian series, respectively, of the Ver- 



1 See summary of Van Hise's report on a preceding page. 



