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MUSEUM OF COMPAKATIVE ZOOLOGY. 



99 



sandstone is said to have been seen. Their geological reasoning could 

 only hold good in a region where uncontorted sedimentary rocks alone 

 occur; therefore we are justified in believing that at this time both 

 Pumpelly and Brooks regarded the copper-bearing traps as metamor- 

 phosed sedimentary rocks. We are not aware that the latter has ever 

 changed his views. 



In 1873, Dr. T. Sterry Hunt* used the term Keweenian group in 

 speaking of the copper-bearing rocks, and suggests that perhaps the 

 copper may have been derived from the oxidation of copper ores in the 

 Huronian schists, while the dissolved metal accumulated in the basins 

 at their base, — a view almost identical with that announced by Shepard 

 twenty-eight years before. " We may here remark that the late re- 

 Bearches of Messrs, Brooks and Pumpelly seem to establish that the 

 great copper-bearing scries of Keweenaw occupies a place between the 

 Huronian schists and the nearly horizontal i*ed and white sandstone of 

 the region which is itself below the Trenton limestone. In all this they 

 have confirmed the previous conclusions of Houghton, Whitney, Hall, 

 and Logan." It may be remarked here, also, that if Prof Whitney's 

 writings have taught anything, it is that the sandstone from Sault St. 

 Marie to the further side of Keweenaw Point, including the copper- 

 bearing rocks, are one and the same formation ; therefore Dr. Hunt's 

 statement is incorrect in this particular at least. In proof of this, one 

 can read his own statement of Prof Whitney's ideas on page 79 of the 

 "Azoic liocks.'* t As we have shown before, Houghton regarded the 

 copper-bearing rocks as eruptive in, and therefore younyjer than, the 

 sandstone of Keweenaw Point, which in 1843 he took as belonging to 

 the "New Red." This is the last published statement that we can find 

 of Houghton's on this point. 



Mr. Brooks, in his Report on the Iron Distincts of Lake Superior, J re- 

 gards it as proved that the copper-bearing rocks are conformable with 

 the Huronian ; the proof was obtained, not from contacts, but from 

 their common dip and strike. He also states : " Against and over the 

 copper series on the north, abut the horizontally bedded lower Silurian 



sandstones As the non-conformahiliti) of the copper-bearing 



rocks and sandstones is doubted by some geologists, it should perhaps 

 be stated that the actual contact was not soon. But the sandstones were 

 observed lying horizontal, and affording not the slightest evidence of 



* Trans. Am. lust. Min. Eng., 1. 331-342. 



t Sec. Geol. Survey of reiin. E, Azoic Rooks, Part I. 



% Geol. of Mich., I. 184, 185. 



r , 



