38 GEOLOGY OF ILLINOIS. 



sandstones. About Lawrenceville there is usually from five to sis feet 

 of brown gravelly clay resting immediately upon the bed rock, and 

 above that from ten to twelve feet of buff or brown clays that are quite 

 free from gravel. 



Stratified Rods. — All the formations that outcrop in this county below 

 the superficial deposits already described, belong to the upper Coal 

 Measures, and include a vertical thickness of not more than one hundred 

 and fifty to two hundred feet. On the Wabash river at St. Francisville 

 there is an outcrop of massive gray sandstone, which I believe to be 

 the same as that found at Hanging-rock Bluff in "Wabash county, and 

 the lowest rock seen in this county. The section here is as follows : 



Ft. 



Shale 8 



Impure iron ore 1 



Thin bedded sandstone and sandy shale 16 



Massive gray sandstone 20 to 25 



Unexposed to river level 10 to 15 



Just below the dam at Lawrenceville on the Embarras river we find 

 the following section, which I believe overlays the beds seen at St. 

 Francisville : 



Ft. 



Brown and bluish-gray argillaceous shale 10 to 12 



Eiuniinous and partly calcareous shale with bands of iron ore and numerous fossils 4 to 5 



Black slaty shale 3 to 5 



Dark gray limestone in the river bed 1 



The fossiliferous bed at this locality contains Lopliophyllum proliferum, 

 Pleurotomaria spJicerulata, P. tabulata, P. Grayvillensis, P. carbonaria, 

 PolypJiemopsis peracuta, Bellerophon Montfortianus, B. carbonarius, B. 

 per-carinatus, Astartella varied, Productus longispinus, Hemipronites 

 crassus, Macrocheilus inhabilis, and joints and plates of Crinoidea. 



At the bridge two miles east of Lawrenceville we find a repetition of 

 the foregoing section, but the bluff is much higher and a greater thick- 

 ness of strata is exposed, giving the following section: 



Ft. 



1. Micaceons sandstone and shale passing downward into argillaceous shale 20 to 25 



2. Bluish-gray calcareous shale, with iron bands and fossils 4 to 6 



3. Black laminated shale, with concretions of black limestone 4 to 5 



4. Brittle dark-gray limestone, weathering to a browu or buff color It to 2 



5. Blue and brown shales, partly argillaceous and bituminous 12 to 14 



About a hundred yards above the bridge, by an undulation of the 

 strata, the limestone No. 4 of the above section is brought down to, 

 and passes under the river bed. This would seem to indicate a rapid 

 dip to the northward, but the re-appearance of the fossiliferous slaale 

 No. 2 of this section on Lamotte creek, in Crawford county, some twenty 

 miles north of this, shows that the apparent dip here is only an undu- 

 lation of the strata, such as may frequently be observed in the Coal 

 Measures of this State. Near the upper end of the exposure here a 

 dike of sandstone from six to eighteen inches in width, cuts transversely 



