216 GEOLOGY OF ILLINOIS. 



The outline of this group is nearly as follows: Entering the county near 

 the northwest corner of township 35 north, range 9 east, it runs nearly south- 

 east to near the south east corner of section 24, and includes the larger part of 

 section 30 township 35 north, range 10 east ; here, it crosses the DesPlaines, 

 and follows down its south bank, on the top of the bluff, as far as to the center 

 of section 29, township 34 north, range 9 east ; here, it passes under the shaly 

 sandstone of the Coal Measures for a short distance, and then accompanies 

 their outcrop up the " Cut-off" to the Kankakee, which it follows, with only a 

 small show upon the south bank, to the mouth of Prairie creek; here it bears 

 more to the eastward, and passes around to the north and east of Wilming- 

 ton, turning south through section 31, township 33 north, range 10 east, and 

 following the north bank of Forked creek to the middle of section 17, town- 

 ship 32 north, range 10 east; here it crosses, and strikes the bank of the 

 Kankakee in section 20, and follows it westward through the county. Forked 

 creek and its cut-off also inclose an island of this group, which occupies con- 

 siderable portions of sections 7 and 18, township 32 north, range lOeast. This 

 group also appears upon the south bank of the river for about a mile below the 

 county line. 



The general dip of the beds is toward the northeast, but there are every- 

 where so great local variations, both in direction and amount, that any attempt 

 to indicate them by figures would be fruitless. This has probably resulted, at 

 least in part, from the softness of the underlying beds. 



Cincinnati Group. The rocks of this group, in Will county, consist of buff 

 shaly argillaceous and magnesian limestones, with pyrite and some chert, a 

 heavy bed of green shaly clay, and blue shaly limestones with some petroleum. 



The bottom beds at Grinton's mill probably belong to this group, but, at 

 this locality, the lower beds of the Niagara approach so closely in character to 

 the upper beds of this group, that it is very difficult to mark the division with 

 certainty. One mile down the DuPage, however, in the southwest quarter of 

 section 16, township 35 north, range 9 east, there is an outcrop of undoubted 

 Cincinnati group. The beds here are light buff, porous, magnesian limestones, 

 with bands of chert nodules. A small Loxonema in the chert was the only 

 fossil observed. The section exposed is from twelve to fifteen feet thick. 

 Near the center of the north half of section 5, township 34 north, range 9 

 east, from eight to ten feet of thin-bedded buff limestone with sandy partings, 

 probably corresponding with the lower part of the above section, have been 

 quarried to a small extent in a hill side. A half mile east of this, in the south 

 half of section 33. township 35 north, range 9 east, from eight to ten feet of 

 thin-bedded argillaceous limestone, with many of the common fossils of this 

 group, form the low bank of the DuPage. These beds underlie those before 



