THE OIL- AND GAS-PRODUCING ROCKS OE OHIO 827 



Drift ... ... 1 1 feet 



Berea grit, bottom at ----- - 460 



Corniferous, Helderberg, and Niagara limestones, 



top at - .... . 1,235 



bottom at .... . 1,921 



Clinton sand, top at - - - - 2,025 



bottom at - 2,045 



Medina (red shales) top at 2.055 



Bottom of well at 2,075 



This makes the red shales lying from 10 to 30 feet below the 

 Clinton sand, the top of the Medina. 



The Lower Helderberg. — Rocks of this age produce gas and 

 oil in one locality, viz., near Jefferson, Ashtabula county. The 

 succession of strata there is shown by the following record of 

 Webb Well No. 1. All measurements were made with a steel 

 line. 



Thickness of rr. . , ■ ., 



formation. Total de P th - 



Drift -------- 33 feet. 33 feet. 



Ohio shales - - 1,671 1.704 



Corniferous and Lower Helderberg limestones - 288 1,992 



Gas sand at --------- - 1,992 



The sand, which is from 30 to 40 feet in thickness, is inter- 

 bedded in the Lower Helderberg limestone. Similar conditions 

 are found in Lucas and Wood counties, in the former of which 

 the sand has been quarried for the manufacture of glass. 1 In 

 the gas field under consideration the sand is moderately coarse, 

 has a light color, and is highly fossiliferous. The gas is found 

 in the top of the formation, and just below lies a large and 

 threatening reservoir of salt water. A number of towns and 

 villages are being supplied with fuel from this field. The oil 

 wells are few in number and insignificant in production. 



THE DEVONIAN. 



The rocks of this age found in Ohio, have been classified by 

 Orton 2 as follows : 



3. Ohio shales ----- 250-3,000 feet 



2. Olentangy shale - 25 



3. Devonian limestone (Corniferous) 75 



1 Ibid., p. 17. * Ibid., pp. 4 and 18-26. 



