308 PALAEOZOIC TIME CARBONIFEROUS AGE. 



In Illinois, the Burlington limestone is underlaid by the "Kinderhook Group," 

 also Subcarboniferous, consisting of sandstone and shale with some local beds 

 of limestone, the whole about 100 fe:t thick. (Worthen.) In Missouri, the 

 Chouteau and Lithographic limestones are regarded by some as equivalents of 

 this inferior group of the Subcarboniferous, rather than of the Upper Devonian 

 to which they have been referred. 



In Tennessee, the lower Subcarboniferous beds are siliceous, as already men- 

 tioned. In eastern Tennessee (which borders on the Appalachian region), this 

 lower or Siliceous Group consists of shales and sandstones many hundred feet 

 thick; in middle Tennessee, it is a siliceous rock 200 to 300 feet thick, more or 

 less calcareous, with some cherty layers, especially to the south, and also inter- 

 calated beds of Crinoidal limestone. These siliceous beds reach south into Ala- 

 bama. The xqiper group in Tennessee, though mainly limestone, has in some 

 parts near its middle a band of sandstone 50 to 100 feet thick. 



The Michigan Carboniferous area appears to have been an independent basin 

 at the time of the formation of the rocks. There are four groups of strata, ac- 

 cording to Winchell : the first, or lower, 171 feet of grits and sandstones, which 

 he has called the Marshall Group ; the second, 123 feet of shales and sandstones, 

 called the Napoleon Group ; the third, 184 feet of shales and marl, with some 

 limestone and gypsum, called the Michigan Salt-group ; the fourth, the Carboni- 

 ferous limestone, 66 feet thick. This limestone is well exposed at Grand Rapids. 



In Ohio, the "Waverly sandstone," usually referred to the Upper Devonian, 

 has been referred in part at least to the Subcarboniferous, and it probably 

 corresponds in horizon with the " Marshall Group" of Michigan and the " Kin- 

 derhook Group" of Illinois. According to this conclusion, there is at the base 

 of the Subcarboniferous a series of fragmental rocks over a very wide region. 



A Subcarboniferous limestone occurs near Lake Utah, in lat. 40° 13' N., long. 

 112° 8' W., containing the characteristic Archimedes. It is an exception to the 

 general fact that the limestone of this age in the Rocky Mountains belongs to 

 the second or Carboniferous period. 



(b.) Appalachian region. — The rocks of the lower group in the Appalachian 

 region directly overlie the Devonian and Catskill beds, and are, in the main, 

 coarse grayish conglomerates and sandstones; those of the upper group are 

 soft shales mostly of a red color. 



The lower group has its greatest thickness in Pennsylvania and Virginia, being 

 2000 feet thick near Pottsville. Through much of the anthracite coal basin it 

 constitutes the encircling hills, as around the Wyoming basin, and in many 

 places forms a grayish-white band over another of red, the latter due to the 

 Catskill beds, — the two thus making a red and white frame, as Lesley says, around 

 the valleys or basins. It thins rapidly to the westward ; the rock retains its 

 whitish color and siliceous character in Virginia. Sandstone beds alternate 

 with the conglomerate ; and in New York these finer layers abound in ripple- 

 marks, and that oblique lamination (fig. 61 e) which is due to contrary currents. 



The shales of the upper group are soft, reddish, clayey beds, easily returning, 

 on exposure, to mud, the original condition of the material. They alternate 

 with sandstone layers, especially in the lower part. At Towanda, Blossburg, 

 Ralston, Lockhaven, Portage Summit, etc., in upper Pennsylvania, the formation 

 consists of two or three thick strata of shale separated by as many strata, 50 to 



