26 GEOLOGY OF ILLINOIS. 



county, but for reasons already given, they do not always hold the same rela- 

 tive position as in the section given below : 



FEET. 



Quarternary deposits (Loess and Drift) 40 to 100 



Coal Measures , 20 " 60 



f St. Louis Limestones 00 30 



Keokuk group. . , .100 " 12 



Lower Carboniferous J 



I Burlington limestone 150 " 200 



[ffinderkook group 100 " 120 



Niagara limestone 00 50 



The Niagara limestone is only found in the southwest part of the county, 

 where its main outcrop is at the base of the bluffs, between Rockport and the 

 south line of the county, and on Six Mile creek, for a short distance up that 

 stream. Where the rock first appears, the upper portion is a rather thin bedded, 

 rough, gray limestone, becoming more massive below, and on Six Mile creek, 

 it is partly a regular bedded buff or brown dolomite, and presents the usual 

 characters of this formation at other localities. It contains a few fossils at the 

 outcrop in the vicinity of Pleasant Hill, among which we obtained fragments 

 of Trilobites, a few fossil shells, too imperfect for determination, and a single 

 specimen of Halysites catenulatus. 



At Mr. Wells's place, on the northwest quarter of section 17, township 7 

 south, range 4 west, the buff colored magnesian beds of this group are exposed 

 about ten feet in thickness, and the rock has been quarried for general use as 

 a building stone in the neighborhood. The beds appear to dip here in an op- 

 posite direction from those at the point where the rock rises so suddenly from 

 beneath the surface of the bottom lands, at the foot of the bluffs, the direction 

 being to the south 20 east, and the angle about 6. On the southeast quar- 

 ter of section 8, in the same township, there is an exposure of about twenty- 

 two feet of this limestone, the lower ten feet being a gray, even bedded lime- 

 stone, and the upper twelve feet a buff colored magnesian rock, closely resem- 

 bling the rock from the Grafton quarries. It is the prevailing rock at Pleas- 

 ant Hill, and forms a limestone bench about thirty feet in hight, above the 

 road, at the base of the bluffs. Two miles north of Pleasant Hill, on a branch 

 of Six Mile creek, the upper part of this limestone is exposed in the bed of the 

 creek, dipping north 30 west, about 2. Only about six feet in thickness is 

 exposed here, and the rock is a regular bedded, brown magnesian limestone. 

 This seemed to be about the most easterly outcrop of this formation, an'd it is 

 here overlaid by the shales of the Kinderhook group. From this point south- 

 westward, to the Calhoun county line, occasional outcrops of this limestone 

 may be seen along the base of the bluffs, and its entire outcrop in this county 

 is restricted to the vicinity of the river bluffs between Rockport and the south 

 line of the county. 



