100 GEOLOGY OF ILLINOIS. 



strata that were penetrated. Both these borings commence below 

 the Eusulina limestone which outcrops in the bluffs of the Embarras 

 from the bridge west of Greenup to the north line of the county. 



In the bluffs of the Embarras, one mile west of Greenup, we find the 

 following section at the bridge on the old National road : 



Ft. In. 



Gravelly drift clay, buff, yellow and ash-gray 32 



Thin bedded micaceous sandstone -' 6 



Argillaceous shales, with a streak of coaly matter 16 



Impure ferruginous limestone, [Fusulina bed) 1 G 



Thin bedded sandstone and sandy shales 15 



Slope covering shales to riverbed 12 



A mile north of the bridge the limestone thickens to three feet or 

 more, and is a nodular gray argillaceous rock, rather more calcareous 

 than at the bridge below, nodular and thin bedded, but containing a 

 few of the fossils that are more abundant in it near the north line of 

 the county. This is the only limestone found in the county, and varies 

 in thickness from IS inches to S or 10 feet, or more, at the different out- 

 crops examined. It is usually too argillaceous to slack freely when 

 burned, and too nodular and irregularly bedded along the Embarras to 

 furnish a good quality of building stone. 



The sandstone underlaying the limestone in the above section affords 

 layers from 6 to 18 inches in thickness, and was used in the abut- 

 ments for the bridge at this point; but not being carefully selected, the 

 shaly layers soon gave way, endangering the whole structure so that it 

 had to be abandoned. 



On the branch north of the town of Greenup, where the oil well was 

 located, the following beds outcrop in the bluff on the south side of the 

 stream : 



Feet. 



Yellow drift clays 10 to 12 



Nodular, brown impure limestone 1* to 2 



Sandy and argillaceous shales, with thin layers of sandstone, to the creek bed 35 to -10 



A short distance above Ryan's ford, and about two miles below the 

 north line of the county, this limestone is well exposed, showing a bench 

 of rough, irregularly bedded, brownish gray, nodular, argillaceous lime- 

 stone, from 8 to 10 feet in thickness, outcropping just above the bed of 

 the river. The upper part of the bed is of a brownish-gray, and the 

 lower part a greenish gray color. Numerous small fossils were found 

 in the limestone at this locality, among which were the following well 

 known species : Athyris subtilita, Terebratula bovidens, Betzia punctu- 

 Ufera, Ehynclionella Osagensis, Spirifer cameratus, S. lineatm, S. piano- 

 convexus, Fusulina cylindrica, some undetermined corals, etc. The lime- 

 stone is underlaid here by a greenish clay shale, of which not more than 

 two feet in thickness was visible above the bed of the river. Descend- 

 ing the river from the ford towards Greenup the limestone gradually 



