468 HISTORICAL GEOLOGY, 



rous shales next above, and the slates, shaly grits, and conglomerates, below, this formation. 

 It is exposed on the western slope and in the west flanking hills of the Blue Ridge, through 

 much of its length, often, by inversion, dipping to the southeast, in seeming conformity 

 beneath the older rocks of the Blue Ridge, but often, also, resting unconformably upon or 

 against them." These statements are cited from the Beprint of the Annual Reports of 

 1835-1841, and Other Papers on the Geology of the Virginias^ by the late AV. B. 

 Rogers, 1884. 



In Tennessee, the Lower Cambrian comprises the " Chilhowee " sandstones of Safford, 

 and beneath these, probably, the Ocoee conglomerates and sandstones. West of Cleveland, 

 in east Tennessee, it includes the lower part of the Knox sandstone of Safford (the Rome 

 sandstone of Hayes, in Georgia), and the thick formation of limestone and shales below ; 

 while the central and upper portions of the Rome sandstone are Middle Cambrian. The 

 same succession occurs near Knoxville. The Upper Cambrian is probably represented by 

 the lower 2000' of the Knox dolomyte. The typical New York fauna of the Upper Cam- 

 brian has not been recognized along the Appalachians in Pennsylvania, nor to the south- 

 west. Lower Cambrian fossils have been observed in the lower part of the Rome sandstone 

 near Rome, Ga., and in the limestones and shales of the Coosa series, in Coosa valley, 

 Alabama, north and south of Cedar Bluff. 



In northwestern Michigan and Wisconsin, south of Lake Superior, the Lake Superior 

 sandstone, on the borders of the lake, rests unconformably on the Keweenaw formation, 

 and is referred to the Cambrian. A broad area of Upper and Middle Cambrian with fossils 

 skirts the Archsean area on the east and south, and consists of crumbling sandstone and 

 arenaceous shale, with, in some places, much green sand (glauconite), and thin beds of 

 limestone ; the maximum thickness is 1000'. The quartzyte occurring in isolated hills in 

 the drift-covered region of AVisconsin in Barron County, and at Baraboo in Sauk County 

 (the Baraboo quartzyte), is made Huronian by Chamberlin and Irving, but Lower Cam- 

 brian by N. H. Winchell. At St. Croix River, the horizontally bedded Upper Cambrian 

 rests on upturned red beds, which are Middle or Lower Cambrian, and are continuous with 

 the pipestone quartzyte of southwestern Minnesota, where Lingulse have been found ; 

 in this quartzyte, the pipestone bed (Catlinite) , used for making pipe bowls by the Indians, 

 is a layer of red argillaceous sandstone about a foot thick ; the rock passing south into 

 Iowa is the "Sioux quartzyte" of C. A. White, and extends 10 miles into Dakota to 

 Sioux Tails. 



With regard to the fact of unconformability with the Archaean at Carp River, Pro- 

 fessor J. D. Whitney states, in a letter to the author of Nov. 7, 1893, that "nothing could 

 be clearer" ; that " along the shores of Carp River and throughout the adjacent region, the 

 sandstone strata are recognized as overlying the well-characterized beds of a much older 

 formation which I designated as the 'Azoic Series.' At Carp River the nearly horizontal 

 unaltered sandstone strata abut against and overlie the vertical edges of a well-marked 

 quartzyte." The Lower Magnesian series of Missouri, excepting the First, or Upper, lime- 

 stone of the series, and the underlying Saccharoidal sandstone, is Cambrian. It consists 

 of alternating strata of dolomyte and sandstone. This Lower Magnesian series of Missouri 

 is the Ozark series of Broadhead. 



The Keweenaw beds were described by Poster and Whitney in 1850, 1851, and referred 

 to the age of the Potsdam or Cambrian. The more recent reports are by Irving (1880, 1883, 

 1885) and Chamberlin (1883) ; and, with special reference to copper mining, by M. E. 

 Wadsworth in 1880. The series consists of an upper division, consisting of ordinary sand- 

 stone and shales, free from igneous material, made 15,000' thick by Irving, and a lower 

 division, 25,000' to 30,000' thick, made up of detrital and igneous rocks, but chiefly the 

 latter. Chamberlin gives the same aggregate thickness, 45,000'. The igneous rocks are 

 doleryte (diabase) with porphyritic and amygdaloidal varieties, gabbros, and also acid 

 rocks as felsyte, felsyte-porphyry, and others. (For a full account of the rocks, see Irv- 

 ing, Report U. S. G. S., v., 4to, 1883.) As estimates of the thickness of upturned rocks 



