4 GEOLOGY OF OHIO. 

 18. Glacial drift 



10. Ohio Shale 



6. Niagara Group. 



17. Upper Barren Coal Measures 



16. Upper Productive Coal Measures 



15. Lower Barren Coal Measures 



14. Lower Productive Coal Measures 



13. Conglomerate Group 



12. Sub-carboniferous limestone, Maxville, Newtonville, etc., 



f lie Logan Group 0-350. "1 



I lid Cuyahoga Shale, 150-450. | 500' ] 

 11. Waverly Group { lie Berea Shale 20-50. f to \ 



I lib Berea Grit 5-160. 800' j 



[ la Bedford Shale '..50-150. j 



I 10c Cleveland Shale. ) 

 . I 10b Erie Shale. \ 250 to 3,000 feet... 



( 10a Huron Shale. j 



9. Hamilton Shale ( Olen'tangy Shale ? ) 



8. Devonian Limestone, Upper Helderberg or Corniferous, 

 including West Jefferson sandstone 



7. Lower Helderberg limestone, or Waterlime, including Syl- 



vania sandstone, 50 to 600 feet 



6d Hillsboro sandstone 



6c Guelph or Cedarville limestone,50-200, 



6b Niagara limestone 



6a Niagara Shale, including Dayton lime- 

 stone, 5 to 100. 



5. Clinton Group, in outcrop, 20 to 75 feet ; under cover, 75 to 1 50. 

 4. Medina shale, in outcrop, 25'; under cover, 50 to 150. 



3. Hudson River Group, 300' to 750 7 



2. Utica Shale, not seen in outcrop, but 300 feet thick under 



cover in northern' Ohio 



1. Trenton limestone, seen only in Pt. Pleasant quarries, if at 



all, in the state 



The Trenton Limestone. 



The Trenton limestone is one of the most important of the older for- 

 mations of the continent. It is the most widespread limestone of the 

 general scale of the country. It extends from New England to the 

 Rocky Mountains, and from the islands north of Hudson's Bay to the 

 southern extremity of the Allegheny Mountains in Alabama and Georgia. 

 Throughout the vast region it is found exposed in innumerable out- 

 crops. As it decays, it gives rise to limestone soils which are sometimes 

 of remarkable fertility; as, for example, those of the famous Blue Grass 

 region of central Kentucky, which are derived from it. It is worked for 

 building stone in hundreds of quarries, and it is also burned into lime 

 and broken into road metal on a large scale throughout the regions where 

 it occurs. 



But widespread as are its exposures in outcrop, it has a still wider 

 extension under cover. It is known to make the floor of entire states, in 

 which it does not reach the surface in a single point. 



It takes its name from a picturesque and well known locality in 

 Trenton township, Oneida county, New York. The small river, known 



