336 THE CAMBRIAN. Ibull,8L 



TLe characters of the sandstone and its relation to the superjacent 

 rock are stated as follows : 



The sandstones of the Keweenaw Bay and its vicinity, and eastward thence to White 

 Fish River, are reddish and often highly argillaceous. At White Fish River the red 

 sandstone is overlain by a light-colored sandstone, which is in turn succeeded by a 

 maguesian limestone, in which are casts of Pleurotomaria. This limestone is the 

 Lower Maguesian of the Wisconsin reports and the Calciferous sandrock of the East- 

 ern States. That it is succeeded in regular order by the fossiliferous limestones of 

 the Trenton, Cincinnati, and Niagara groups was long since shown, and has been 

 demonstrated anew of late years by the labors of the geological surveyors of Wisconsin 

 aud Michigan. There thus seems little room for doubt as to the correctness of the 

 view held for years by a succession of geological workers in the Lake Superior region 

 from Owen to Rominger, viz, that in the Eastern sandstone we have to do with the 

 same formation, or with its downward continuation, as the fossiliferous Cambrian 

 sandstone which, in the Mississippi Valley, forms the base of the Paleozoic column. 1 



The Western sandstones, or those of the Apostle Islands and the ad- 

 joining coast of Bayfield, Douglas, and Pine Counties, are composed of 

 a horizontally placed sandstone, closely resembling in character the 

 Eastern sandstone of Keweenaw Point. The exposures of the sand- 

 stone are almost entirely restricted to the vicinity of the shores of the 

 lake, on the mainland, and the Apostle Islands, and have never been 

 seen reaching more than 50 feet above the lake level. Farther west, 

 however, in Douglas County, the horizontal sandstone reaches to 3G0 

 feet above the lake. 2 Prof. Irving states that the prevailing color of 

 this rock is some shade of red, from bright brick red to a brownish 

 red Or purplish red. Pinkish, straw-colored, and even nearly pure 

 white varieties occur, either blotching the ordinary red rock in small 

 patches, or occurring in layers from an inch to 2 or 3 feet in thickness. 

 A section typical of many of the cliff exposures of the lake shore is as 

 follows : 



Ft. In. 

 Red marly clay (Quaternary) 5 



Shaly sandstone, in layers from one-fourth to one-half inch thick ; 

 light reddish to brown, medium-grained, chiefly made up of 



subangular quartz grains . 4 9 



Compact sandstone 2 



Shaly sandstone 3 



Compact sandstone ; pinkish and moderately coarse-grained, 

 chiefly made up of quartz grains, but many white clay spots, 

 indicating the decomposed feldspar 2 



14 



The shaly and massive layers are, however, not constant, and either will grade 

 into the other in a short distance, the shaly kinds being often merely a result of 

 weathering. Often the massive layers have a thickness of 5 feet and upwards, and 

 lie together in considerable thicknesses without intervening thin-laminated seams. 

 In many places round bunches of red clay, from an inch to several feet in diameter, are 

 seen imbedded in the massive sandstone. In other case« the clay lies in limited and 



» Op. cYt., pp. 351, 352. 



2 The Lake Superior Sandstone. | Geology of the Eastern Lake Superior District. ] Geol. Wiscon- 

 sin, vol. 3, 1880, p. 207. 



