XXXYI OUTLINE OF THIS MONOGKAPH. 



igneous rocks of basic or iutermediate chemical composition ; and finally, the grain and character 

 of the groiindmass, and in some slides the presence of plagioclase microlites disposed iu oval lines 

 point directly to an igneous origin and to consolidation at the surface. The conclusion is reached that 

 the Hemlock formation of the Fence River area is composed of a series of old lava flows varying in 

 composition from acid to basic. 



Section VI treats of the Grovelaud formation. This is of wide extent throughout this part of 

 the Crystal Falls district, but its outcrops are limited to three localities. Its distribution has been 

 determined by means of its magnetic properties. It is not topographically prominent, except in the 

 Michi"animo Mountain area, where it forms part of Michigamme Mountain. In the Fence River area 

 it is probably not folded. It there dips to the east. At Michigamme Mountain it is found in several 

 well-marked folds. The thickness of the formation is estimated to be approximately 500 feet. The 

 rocks are interbauded ferruginous quartzite and actiuolite and griiuerite schists, which still contain 

 evidence of detrital origin. 



Chapter Y treats of the Northeastern area and the relations between the Lower Marquette and 

 the Lower Menominee. The territory included in the Northeastern area extends from the northern- 

 most outcrops of the Fence River area to the northern end of the Republic trough, a distance of about 

 11 miles. Outcrops are scarce throughout this area, and the main conclusions are drawn from the 

 magnetic work. Through the structural and lithological results of the magnetic work the gap 

 between the Marquette and the Crystal Falls district is bridged, and it is shown with a high degree 

 of probalnlity that the Negaunee iron formation of the Marquette range is identical with the Groveland 

 iron formation of the Feloh Mountain range. 



Chapter VI treats of the Sturgeon River tongue. In the southeastern part of the Crystal 

 Falls district and just north of the Feloh Mountain range a tongue of fragmental rooks extending 

 eastward has been studied. The extreme length is 12 or 13 miles. Its width at its eastern end is 1* 

 miles; to the west it widens rapidly. It is bounded both to the north and to the south by Archean 

 granites and schists ; to the east it is overlain by Paleozoic sandstones and limestones ; and at its west 

 end it is covered by glacial deposits. Within the tongue two small granite islands occur. The 

 Archean or Basement Complex rocks comprise gneissoid granites, hornblende-schists, and biotite- 

 schists, which are cut by dikes of greenstone and granite, and veins of quartz. The sedimentary rocks 

 comprise conglomerates, arkoses, quartzites, sericite-sohists, clay slates, rocks that are probably 

 tufaceous, dolomitic limestones, and calcareous sandstones and slates. They may be divided into a 

 conglomerate series and a dolomite series. From the distribution of the exposures of the two series 

 it is concluded that the conglomerate series is the older, and that conformably above it follows the 

 dolomite series. The two form a westward-pitching syncline. The conglomerate series and the 

 dolomite series are correlated respectively with the Sturgeon quartzite and the Randville dolomite of 

 the adjoining Felch Mountain range. 



