130 THE MARQUETTE IKON-BE AKIiJ^G DISTRICT. 



Van Hise, C. R. Pre-Cambri.iii geology of the Lake Superior region. Ibid., 

 pages 489-512. \Vith maps. 



In this ])apei', which is explauatory of a trip made througli the iron 

 districts of Lake Superior with some members of the International Con- 

 gress of Geologists, the author gives descriptions of the general character of 

 the Basement Complex and of the Upper Huronian and Lower Huronian 

 series. Very little is contained in these descriptions that had not been 

 given in earlier publications, of which it is largely an abstract. The maps 

 ai-e reproductions of those published Ijy Brooks, Irving, G. H. Williams, 

 Pumpelly, and Van Hise. 



1892. 



Van Hise, C. K. The iron ores of the Marquette district of Michigan. Am. 

 Jour. Sci. (3), Vol. XLIII, 1892, pages 110-132. 



In this paper Van Hise gives a resume of the results of a preliminary 

 examination of the Marquette district. 



Two ore-bearing formations are recognized in the district^one belong- 

 ing in the Lower Marqviette and the other in the Upper Marquette series, as 

 defined by the author. 



The ore deposits of the Lower Marquette series consist of the banded 

 jasper and ore so many times described. The jasper is not a fragmental 

 rock. It is composed of individualized silica, forming bands which, when 

 white, are known as chert. When the grains are stained with red oxide of 

 iron they give rise to jasper. The siliceous bands are not regular in thick- 

 ness. The}" sometimes extend for long distances with a nearly xmiform 

 widtli. Sometimes they wedge out abruptly. Often they occur as rows of 

 lenticular masses. Near the top of the formation the silica is nearly all 

 jasperized. Farther down, as a rule, it is more cherty, until in the loAver 

 portions of tlie formation the siliceous l^ands are white. 



Actinolite-magnetite-schists are also associated with the ores, especially 

 where these are magnetites. 



Another and important component of the ore-bearing formation is a 

 cherty carbonate of iron. This lias been found most frequently where the 

 formation dips under a greenstone. Cutting these rocks are bosses and 



