GEOLOGICAL EXPLORATIONS AND LITEllATrRE— 1888. 117 



WiNCHELL, Alkxander. Tbc Marqiit'ttc iron loiiidii. Ihid., paf^es JTl-lS.'). 



Ill luaiiv points Alexander WiiielicU (lititers with his l)rotht'r as to the 

 signitioauce of the facts observccl. In other points the two are agreed. 



Among the ))oints lirouglit out Ijy Alexander Winrliell are the inter- 

 stratiiieation of the ore beds with the associated rocks, and the occurrence 

 of a conglomerate above the on; beds in the Lake Superior mine. 



The downward succession of beds in the Ishpeming syncline is thought 

 to be as follows: red slate; black slate and mixed ore; ore; talcose rock; 

 diorite. The red slates are banded hematite and jasper; the black slates 

 are magnetic jaspers; and the talcose rock is an argillitic variety, as is also 

 the miner's "soap-rock." 



The Deer Lake conglomerates are regarded as sedimentary because 

 " they contain foreign pebbles." 



The contact of the granite and quartzite north of Micliigamme, where 

 N. H. Wiiu-hell reported tlie existence of a conglomerate, is given a peculiar 

 interpretation (p. 177): 



Immediately in coutact with this [the granite] is a greenish (luartzj^te, wliieh 

 passes by transition into the granite. * * * It might also signify that the 

 "granite" was originally a sedimentary rock, but, containing more feldspar-making 

 elements than the quartzyte, metamorphism changed it to a rock of the granite series, 

 but could not make anything but a quartzyte of the overlying beds. 



Xear the Buffalo mine the author saw a black argillite, which was. 

 thought to be unconformable on (piartzite. 



After describing other phenomena seen l)y him, Winchell sums up his 

 study in these conclusions (p. 1 SA) : 



Tlw Miirquette Iron-hearing rocks are not of Huronuin mje. * * * That they 

 are older than Huronian is shown by a fourfold line of evidence. («) The rocks arc 

 different. In the original Huronian the argillites are almost exclusively black and 

 carbonaceous or magnetitic, instead of bluish or ashen and luematitic. They are more 

 prevalently siliceous or flinty. The quartzytes attain a more enormous development, 

 are much purer, especially the upper, and hold position entirely above the argillitic 

 member, (b) The Canadian Huronian succeeds immediately beneath the Palceozoic system. 

 The Marquette strata do not. The Marquette strata are succeeded immediately 

 downward by crystalline schists. The Huronian strata are not. (c) Some evidences 

 exist of an unconformable overlyiny sub-Palwozoic system in the Marquette region. I 



