REVIEWS 



451 



Van Hise and Bayley' describe and map the geology of a portion 

 of the Menominee iron district of Michigan. 

 The pre- Cambrian succession is as follows : 



Algonkian 



I 



Upper Menominee 



Unconform ity 

 Lower Menominee 



Unconfo7-)nity 



Archean 



r 



I 



Hanbury slate. 



Vulcan formation, subdivided 

 into the Curry ore-bearing 

 I member, Brier slate, and 

 I Traders ore-bearing mem- 

 L ber. 



f Negaunee formation. 



■\ Randville dolomite. 

 I 

 [^Sturgeon quartzite. 



Granites and gneisses, cut by 

 granite and diabase dikes. 

 I Quinnesec schists, cut by acid 

 I and basic dikes and veins. 



In general the Algonkian rocks constitute a trough bounded on 

 the north by the Archean rocks. 



The Archean. — The Quinnesec schists are dark green or black 

 basic schists and spheroidal greenstones, cut by large dikes of gabbro, 

 diabase, and granite, and by smaller dikes of a schistose quartz por- 

 phyry. These occur in two areas, one along the Menominee River to 

 the south of the Huronian rocks, and another in the west-central end 

 of the district. 



Bordering the Algonkian trough on the north is a complex of 

 granites, gneisses, hornblende schists, and a few greenstone schists, all 

 cut by dikes of diabase and granite. This complex is called the 

 "Northern Complex." Most of the Archean rocks are igneous. 

 Although there is no evidence of this, some of the fragmental tuffs 

 may have been water-deposited. The Quinnesec schists and the 

 Northern Complex are called Archean because they resemble lithologi- 

 cally other areas of Archean rocks in the Lake Superior country, and 

 they both underlie the Algonkian series. The Northern Complex 

 underlies the series with unconformity. The Quinnesec schists have 



'The Menominee special folio, b)' Charles R. Van Hise and S. W. Bayley: 

 Geological Atlas of United States, F'olio No. 62, U. S. Geol. Surv., 1900. 



