230 GEOLOGY OF ILLINOIS. 



cliert, which at one point attains a thickness of about two feet. This is 

 succeeded by silicious shale and sandstone, extending upward to the 

 fire clay or septaria-like limestone below coal No. 2. 



The limestone over this coal splits into irregular conchoidal fragments 

 on exposure to atmospheric influences, and at Coal Valley, and at some 

 other points is filled with a peculiar fucoid resembling the Cnmla Galli 

 of the Devonian rocks. The black shales over the coal afford some 

 fossils, among which the Productus muricatus and Chonetes mesoloba 

 were common, and associated with them we obtained Distinct nitida, 

 Ehynchonella Uatonicvformis, Lima retifera, Petrodus occidentalis and 

 Listracantlms liystrix. Undetermined species of Nautilus, Orthocents, 

 Aviculopecten and Pleurophorus were also obtained here. 



An analysis of this coal, from a specimen taken from the Carbon Cliff 

 mines, is given on a preceding page, and shows about the average- 

 quality of this seam in the vicinity of Rock river. 



About three miles north-east of Coal Valley, and just over the line 

 in Henry county, on the S.W. qr. of Sec. 19, T. 17 N., It. 1 east, this 

 seam has been opened and is now worked at what is known as the 

 Parks mines. The coal is here about five feet thick and of excellent 

 quality, breaking into regular quadrangular pieces. The chert band 

 over the coal is a foot or more in thickness at this point, and the beds 

 of the little runs are full of its broken fragments. 



On Walnut creek, which empties into the Mississippi just below An- 

 dalusia, about one hundred feet in thickness of Coal Measures may be 

 seen directly overlaying the Devonian limestone. The beds exposed 

 here show the following succession : 



No. 1. Clay shales passing upward into sandy shales, the lowest layers bituminous 8 to 10 feet. 



No. 2. Coal, No. 2 1, 



No. 3. Fire-clay 2 to 3 



No. 4 X Sandy shales and sandstone 20 ' ' 30 



No. 5. Dark-blue silicious limestone 1 ' ' 3 



No. 6. Bituminous shale 4 " 8 



No. 7. Goal, No. 1 3 



No. 8. Fire-clay 2 " 3 



No. 9. Shales, argillaceous, silicious and partly bituminous, -with a thin seam of coal. . .50 "60 



No. 10. Devonian limestone exposed 10 



The upper coal seam in the above section had been opened at one 

 point in the bluffs of the creek, but proved to be too thin to be profit- 

 ably worked, and was subsequently abandoned. 



On Coal creek, another small stream still further south, there are 

 about two hundred feet of Coal Measures to be seen, which probably 

 include the horizon of the three lower seams of coal. The section here 

 shows about the following order : 



No. 1. Sandy shales 30 to 40 feet. 



No. 2. Bituminous shale, with about one foot of coal near the middle of the bed (No. 3?) 8 " 10 " 

 No . 3. Sandstone, thin bedded in the upper part and thicker below 30 " 40 " 



