GEOLOGICAL EXPLORATIONS AND LITERATURE— 1888. 115 



WiNCHKLL. N. H. The iron-bearing rocks at ^Maniuette, Michigan. Geo!, 

 and Nat. Ilist. Surv. of Minnesota, Sixteeutli Ann. Kept, for 18S7, St. Paul, 1888, 

 pages 40-54. 



A. Wiucliell and N. H. WiuclicU made a rapid trip tliruuiih tlie Marquette 

 district in the summer of 1887, and ])ublislied records of their observations 

 independently. At Negaunee, Ish})eming, and Marquette, X. H. Winchell 

 made a few observations that are of some interest. In the Negaunee area 

 the mines east of the town were the special objects of study. Here a gra- 

 dation is reported between coarse quartzites, through an impure hematite 

 banded with chalcedonic silica, into an earthy, hematitic, jasperoid rock. 

 "This shows a common origin for them all rather than a chemical or 

 eruptive source for the jaspilyte and not for the others " (p. 42). At the 

 Iron Cliffs mine siderite was seen associated with the hematite. The most 

 important observations were made in the Cascade area, where there is 

 described as unconformably overlying the iron formation a quartzite-cou- 

 glomerate. It contains pebbles of red jasper, chert, and hematite. This is 

 the conglomerate so frequently described by the earlier geologists. N. H. 

 Winchell appeai-s to have been the first to have noticed that it lay uncon- 

 formabh' upon the iron formation. It is regarded at Cascade as the southern 

 rim of the syncline whose northern rim is in the quartzite bluffs of Teal 

 Lake. From the character of tlie pebbles found in this conglomerate, "it 

 is apparent," writes the author, "that the iron-ore formation iiuisf have heen 

 constituted in pretty ucarlij its present state prior to the fonnatioii of the 

 conglomerate'" (p. 44). This conclusion, it will be noticed, is the same as 

 that arrived at by Wadsworth and by Irving. A little farther west, at the 

 Saginaw mines, in the Ishpeming- district, the same unconformable relations 

 were observed l)etween an overlying conglomerate and the underlying iron 

 formation. Two figures are given illustrating these unconformities, in the 

 first of whicli the conglomerate is laljeled Potsdam (p. 45). It is evident 

 that the author did not at this time perceive the full meaning of the facts. 



North of Ishpeming the conglomeratic greenstones of Deer Lake were 

 examined. They are described as soft, quartzless, schistose rocks, without 

 any bedding structure that can be attributed to sedimentation. They 

 appear to be unconformably beneath the quartzite. These conglomerates 



