MUSEUM OF COMPARATIVE ZOOLOGY. 



15 



■with tlic axes of the folds Avhich constitute a regular system of flexures 

 coextensive with the distribution of the Iluronian series in the vicinity 

 of JMarquettGj are, in reaHty, indigenous greenstone, and a portion of tho 

 development of the diorito upon which repose tlie npper members of the 

 Series, and which, as will hereafter be shown, is uncovered along most of the 



ridges of the region." (/. c, p. 21)G.) 



(( T 



The position of the beds of specu- 

 lar iron ore has already been stated to be at the top of the Hnronian series, 

 .... intcrstratificd with talcose and argillaceous schists. Sharing the 

 plications of tlie entire series, these specular schists, as they may prop- 

 erly be called, are accordingly folded into synclinal basins and anticlinal 

 crests." (/. c, p. 21)9.) " It has been shown that the iron ores of the Hu- 

 ronian series in Michigan arc essentially schists and heavy-bedded strata, 

 in which none of the phenomena of aqueous deposits formed by precipita- 

 tion from water on the one hand, or by dctrital accumulation on the 

 other, arc wanting. They exhibit not only stratification, anticlinal and 

 synclinal folds, but are invarial)ly traversed by systems of joints, and at 

 many points exhibit a perfect slat}^ cleavage. The intimate connection 

 between tho grceubtones, hornblende rocks, and aluminous and magne- 

 sian silicatcd schists of the ferriferous series, has already been indicated 

 in general terms, these rocks not only alternating with, but passing into 

 each other." (/. c, p. 302.) *' Chemical reactions in crystalline sedi- 

 ments resulting from the disintegration of crystalline silicatcd rocks, and 

 operated upon by carbonated waters, are amply capable to have pro 

 dnccd the lithological conditions of augitic rocks, clay-slates, schalstone, 

 and other schists, together witli the oxidized ores of iron intercalated 

 with greenstone among the ancient crystalline rocks of Nortli America 



as well as of Europe From a stratigraphical point of view, while 



evidence is elsewhere often obscure, the Hnronian greenstone, schists, 

 and iron ores of Northern Micliigan, in the absence of close attention to 

 their special chemical conditions, exhibit sedimentary and metamorphic 

 phenomena adequate to render quite untenable, it is believed, tho theory 

 of the exotic character of any portion of them." (I.e., p. o03.) The 

 granite is also regarded as indigenous by Dr. Kimball. 



Mr. J. W. Foster, in 180-3,* states: "The Iron Eegion consists 

 of an assemblage of rocks of various kinds, sucii as argillite, talcose, 

 chlorite, and hornhlcnde schists, quartzites, and occasionally dolomites, 

 all of which are supposed to be of metamorphic origin, intermingled 

 •^dth rocks whose igneous origin can hardly be doubted, consisting of the 



* Geology and Metallurn;y of the Iron Ores of Lake Superior, by J. W. Foster 

 and J. r. KinikiU, New York. 



