382 PALEOZOIC TIME. 



Carboniferous. 



Subcarboniferous. — Consisting of— 1st, "Burlington" subcrystalline encrk 

 nital limestone, 100 feet or more; 2d, " Cherty" limestone, 100 feet; 

 3d, " Keokuk" bluish-gray limestone, with thin beds of shale, 40 feet, 

 and calcareous shale filled with " geodes," 40 feet ; 4th, " Warsaw" 

 magnesian limestone, succeeded by shaly limestone and coarse, cal- 

 careous sandstone, 40 feet ; 5th, " St. Louis" limestone, commonly 

 brecciated and concretionary, in some parts compact, 20 feet or 

 more : total, 340-400 feet. 



Carboniferous. — Shale, sandstone, clay, and limestone, less than 500 feet. 



4. Illinois Section. 

 Lower Silurian. 

 Potsdam, Calciferous Epoch. — Buff magnesian limestone, with beds of earthy 



hydraulic limestone, 100 feet or more. 

 Trenton, Ghazy Epoch. — " St. Peter's Sandstone," brown and white friable 



sandstones, in some places concretionary, 150 feet. 

 Trenton Epoch. — " Trenton" and " Galena" brown magnesian limestones, 



thin-bedded blue limestones, and massive gray granular limestones, 



300 feet. 

 Hudson, Hudson Epoch. — Shales, shaly sandstones, and dark-blue limestone, 



100 feet. 



Upper Silurian. 



Niagara. — Buff and gray magnesian limestone, some cherty beds, 300 feet. 



Devonian. 



Oris k any. — Quartzose sandstone, becoming locally calcareous, 50 feet. 

 Hamilton, Hamilton Epoch. — Coralline limestone and shale, dark-colored fetid 

 limestone, 120 feet. 

 Genesee Epoch. — " Black Slate," bituminous shales and slates, 40 feet. 



Carboniferous. 



Subcarboniferous. — Consisting of — 1st," Kinderhook" arenaceous and argilla- 

 ceous shales with local beds of limestone, 100 feet ; 2d, " Burlington" 

 light-gray limestones with chert, and brown, arenaceous limestones, 

 200 feet; 3d, "Keokuk" calcareo -argillaceous shales with geodes, 

 gray limestones, and chert, with seams of stratified marly clay, 100 

 feet ; 4th, " Warsaw" and " St. Louis" bluish-gray limestone, concre- 

 tionary and brecciated beds, impure limestones and clay shales, mag- 

 nesian limestone, 200 feet ; 5th, massive " Ferruginous" sandstone of 

 even texture, 100 feet ; 6th, " Chester" limestones, separated by heavy 

 beds of clay shale, which pass locally into sandstone, 250 feet : total, 

 950 feet. 



Carboniferous, Millstone-Grit Epoch. — Sandstone and conglomerate, 300 feet. 

 Coal Measures. — Sandstones and shales, with thin bands of limestone 

 and five or more coal-seams, 900 feet. 



