REVIEWS 8 1 



marble is seen at Lake Ogishke-Muncie and at Pjke Rapids on the 

 Mississippi. 



The Lower Keewatin was terminated by a period of extensive 

 folding and intrusions of granite and basic rocks. 



The Pewabic quartzite belongs with the Keewatin, but whether to 

 the Lower or Upper Keewatin is not known. This formation includes 

 altered quartzites and iron-ores between the granite and gabbro in the 

 immediate vicinity of Birch Lake and small patches of similar rocks in 

 Sec. 30-62-10; on the south shore of Disappointment Lake ; on the 

 north shore of Fraser Lake ; on the south shore of Gabbemichigamma ; 

 at Akley Lake, forming the so-called Akley Lake series extending 

 from the west side of Sec. 34-65-5 to the eastern part of Sec. 27-65-4. 



The Upper Keewatin occurs in troughs in the Lower Keewatin, and 

 particularly in one main trough the axis of which is traceable from 

 Vermilion Lake to Saganaga Lake. The northern arm of this syncline, 

 consisting of granites, gneisses, associated mica-schists, and in some 

 places earlier greenstones, extends from the northern part of Vermilion 

 Lake through Basswood Lake to the northern side of Hunter's Island. 

 The southern arm, consisting of Lower Keewatin green-schists and 

 other schists, penetrated by the granite of the Giants Range, extends 

 from Pokegama Falls on the southwest toward the northeast, until cut 

 out by the encroachment of the gabbro from the south. The Upper 

 Keewatin consists very largely of conglomerates, but also includes 

 graywackes, argyllites, quartzites, and jaspilites, in general coarser than 

 those of the Lower Keewatin. Volcanic rocks are less important than 

 in the Lower Keewatin, although still present. There is no general 

 order of succession in the Upper Keewatin excepting that it can be 

 said that it is in general conglomeratic at the bottom. 



After Upper Keewatin time both the Lower and Upper Keewatin 

 were subjected to another folding, the axis of which had a general 

 parallelism with the earlier folding, with the result that the Upper Kee- 

 watin lies in narrow synclines in the Lower Keewatin and in places 

 is nearly or quite vertical. 



Associated with the Keewatin rocks are granites of at least two 

 periods of intrusion, one later than the Lower Keewatin and one later 

 than the Upper Keewatin. The later granite is believed to be repre- 

 sented by the higher parts of the Giants Range and the Snowbank 

 Lake granite. The earlier granite is represented by the granites at 

 Kekequabic Lake, Saganaga Lake, Basswood Lake, Burntside Lake, 



