278 I. C. WHITE DEEP WELL NEAR MCDONALD. PENNSYLVANIA 



Thickness Total 



feet feet 



White slate 650 5.200 



Black slate 120 -".320 



Black shale 200 5,520 



White slate 14f\ 5,660 



Limestone < Selinsgrove) 20 5,680 



Black lime i Selinsgrove) 108 5.788 



Black slate < Marcellus I 22o 6.00S 



Black lime < Corniferous) 15 0.023 



Flint < Corniferous i 22 0.015 



Sand, grayish white < Oriskany i 7 6.052 



The identifications in parentheses are the writer's. 



Discrssiox OF the Sectiox 



The interval in the Geary well from the base of the Berea Grit (1,622 

 feet) to the top of the Corniferous limestone (6.008 feet) is 4,386 fee:, 

 while on the south shore of Lake Erie, near Elyria. Ohio. 115 miles to 

 the northwest, this same interval is only 800 feet. These intervening 

 Devonian shales, however, increase rapidly in thickness southeastward, 

 since at Akron. Ohio, only 35 miles from Elyria. they have a thickness 

 of 1,862 feet, an increase of 30 feet to the mile : while from Akron to 

 the Geary well, a distance of 80 miles, this thickening ( 1.862 feet to 4. 

 feet). 2.524 feet, continues at only the slightly greater rate of 31% feet 

 to the mile. This southeastward thickening of 31% feet to the mile 

 from the region of Akron will furnish a convenient measuring rod for 

 estimating the depth at which the Corniferous limestone may be found, 

 and consequently the Clinton and Trenton petroliferous rocks below, 

 over the present oil and gas fields of western Pennsylvania and West 

 Virginia. According to the elder Orton. the top of the Corniferous 

 limestone falls from 225 feet below tide at Elyria to 925 feet below at 

 Akron, or at the rate of 20 feet to the mile, while from Akron to the 

 McDonald region the descent is at the rate of 40.3 feet per mile, or 

 double the rate to Akron, since the top of the Corniferous lies at 4. 

 feet below tide in the Geary well. This rapid clip of the lower forma- 

 tions should lead to the accumulation of some oil and gas pools in the 

 porous zones of the Clinton and Trenton petroliferous horizons along 

 the interrupted or terrace structural belts of these horizons between 

 Akron and McDonald ; and since the Geary well is located on a well- 

 marked dome in the surface rocks which lias proven very prolific in all 

 of the higher porous sand reservoirs, gas will most probably be found 

 with very high rock pressures in the Clinton and Trenton horizons at 

 this location, should the rocks in question have sufficient porosity to 

 affoid good reservoir capacity. 



