GEOLOGICAL EXPLOIJATIONS AND LITEKATURE— 180L 127 



Dr. Wadsw'ortli'f?, and makes his .sediiueiitary rocks eruptive and liis erup- 

 tive ones sedimentary" (jjp. 123-124:). 



The reiuainder of the paper is devoted luaiulv to tlie correhition of the 

 several Iluroniaii areas in the Lake Superior region, and to a discussion of 

 principles of nomeuclature. Tlie terms Upper Marquette and Lower Mar- 

 quette are u.sed l)y the author to designate those portions of tlie Ilurouian 

 above and below tlie uneonfonnity in the Marquette district, and the.se 

 together comprehend all the Algoukian series in this district. Below the 

 Lower Marquette is the Fundamental Complex of schists, granites, etc., 

 (the Archean rocks), and above the Upper Hurouian lies the Potsdam 

 sandstone. 



( )f course, where the Upper Marquette is in contact with the Archean 

 there are conglomerates and unconformities between the two series, ju.st as 

 there are between the Archean rocks and those of the Louver .Alanpiette 

 series. In each of the two series there is believed to occur an iron-bearing 

 foiTnation. The banded jaspers and ores immediatelv under the conglom- 

 erates belong in the Lower ^Marquette, and the cliertA' ores of the Dalilta, 

 Wetmore, and Beaufort mines, all of which are in black slates, l>elong 

 in the Upper series. 



Wausworth, M. E. a .sketcli of the geology of tlie ^larcjiiette auil Keweeuawan 

 districts. Along the bowstring or soutli shore of Lake Superior. Published by 

 Geueral Pass. Dept., Duluth, South Shore and Atlantic Railroad, 1891, pages 77-01. 



Li a second edition of the little handbook of the Didutli, South 

 Shore and x\tlantic Railroad we find Wadsworth's view^s on the oi-igin and 

 relations of the Marquette rocks ra])idh' clianging, as the result of the 

 studies by the Michigan survey, of Avhich he had been the chief for several 

 years. 



Instead of classing all the formatiims of the district in the one "Azoic'' 

 group, the author separates them into three divisions, naming them the 

 Cascade, the Repuljlic, and tlie ITolvoke formations. 



In the Cascade formation are placed the hornl)lende-schists Avhicli are 

 invaded by granite and other eruptive rocks south of Palmer, and certain 

 detrital rocks composed of their debris, besides the eruptive jaspilites and 



