118 THE MARQUETTE lEOl^-BEAEING DISTRICT. 



refer here l)otli to tlie niiooiitbrmability describeil in the * * * vicinity of the 

 Baffah) mine, and to Major Brooks's l)ri(>f notices of highly carbonaceous black slates 

 occiii)ying a i)ositiou higher than the Mar(iuette argillytes. (f?) Proof is to be adduced 

 in this report of the unconformable subterposition of the Vermilion iron schists relatively 

 to the Animike slates. If the Marquette and Yermillou rocks are mutual equivalents, 

 the former nuist liold position beneath the same system — that is, beneath the Huronian. 

 The Marquette iron-bearing roclcs belong to a system not yet defined. If they underlie 

 the Huronian they equally overlie the Laurentian. They are not separated from 

 the Laurentian by a structural uucouformability, but by the evidences of a long inter- 

 vening lapse of time and a most important change in the action of the geologic 

 forces. Strata fully crystalline and strata essentially earthy, though fou.ul in con- 

 formable juxtaposition, must necessarily belong to two different ages and modes of 

 geological activity. 



For this "'older svstem" in Minnesota the iiuthor suggests the name 

 Marqnettiau (p. 3Go). 



1S90. 

 Wadswokth, M. E. a sketch of the geology of the Mai'quette and Kewee- 

 nawan districts. Along the south shore of Lake Superior. Published bj- Duluth, 

 South Shore and Atlantic R. R., 1890, pages 65-^2. 



In 1890, after having- been appointed State geologist of Michigan, 

 Wadsworth ])ublished a very interesting article, which, though written for 

 the traveling public, gives a succinct and strictly scientific account of the 

 geologv of the iron and copper disti'icts of Michigan from the author's 

 point of view. 



All of the rocks under the Potsdam sandstone are placed in the Azoic 

 svstem. Thev are stated to have been formed in three wars: (1) By 

 mechanical means; (2) by eruptive, igneous, or volcanic agencies: and 

 (3) by chemical action. 



The rocks of mechanical origiii are the detrital quartzites, argillites, 

 gneisses, schists, conglomerates, etc 



These rocks were invaded by eruptive material forcing its way irregularly through 

 the soft sedimentary materials, indurating them, bending their planes of deposition, 

 <;hanging their color, and sending tongues, arms, and dikes through them in every 

 direction. It has also been protruded through the schi.sts in large masses, contorting 

 them and tearing them across, and oftentimes ending in small arms or branches. 

 This eruptive rock is now very greatly metamorphosed, and is termed jaspilite. Like 

 the siliceous eruptive rhyolites and felsites, it is generally more or less banded in its 



