THE MARQUETTE IRON-BEARING DISTRICT OF 



MICHIGAN. 



By C. R. Van Hise and W. S. Bayley. 



INTRODUCTION. 



This report is a final account of tlie Marquette district, the oldest 

 important iron-producing area of the Lake Superior region. Already two 

 detailed reports have been issued upon it by the Michigan State survey. 

 The first, by Maj. T. B. Brooks, published in 1873, was a faithful account 

 of the structural and economic geology of the part of the district producing 

 iron ()re ;it that time, no attempt being made to completely map the area. 

 The intrusive character of most of the greenstones and the physical break 

 existing between the Upper Marquette and Lower Marquette series were 

 not recognized. While for closely studied localities Major Brooks's map- 

 ping is remarkably accurate, it was not possible under the circumstances 

 to fully determine tlie general succession. The second report, by Dr. 

 Carl Rominger, was published in 188 L This report is accompanied Ijv an 

 areal map of the district from Lake Superior to 1 mile into R. 28 W. The 

 topography is carefully indicated by hachures, and the areal distribution of 

 the more important formations is delineated with a fair degree of accuracy, 

 showing that the district had been traversed with great patience. However, 

 all quartzites are placed together, without reference to their age, and the 

 same is true of the slates. The map is not accompanied by any sections. 

 It is therefore to be considered as a lithological rathei- than a stiiictural map. 

 Many other papers upon the Marquette district, of greater or less impor- 

 tance, have been published by Wadsworth, hnnng, Pumpelly, and others. 



MON XXVIII 1 1 



