830 /. A. BOWNOCKER 



county where the formation exists, the production in commercial 

 quantities is limited to Lorain, Medina, Trumbull, Columbiana, 

 Stark, Jefferson, Harrison, Belmont, Guernsey, Monroe, Noble, 

 Vinton, Perry, Athens, Morgan, and Washington counties. 



The Logan group. — The relative position of this group and the 

 Berea is shown by the following skeleton record of a well on the 

 Mead farm in the Elk Run Pool, Washington county. 



( top at 1,200 feet. 



bottom at 1,280 



top at 1,450 



bottom at 1,500 



Logan Mountain limestone - \ top at 1,510 



Salt sand - 

 Maxton sand 



group 



Berea grit 



(" Big lime ") - ■ ( bottom at 1,545 



top at 1 ,560 



i,73o 



j top at 2,124 



I bottom at 2,138 



( top at 

 Big Injun series - - i , ^ 



[_ & ' { bottom at 



This shows that the two formations are about 400 feet apart, 

 and as has already been stated the interval is occupied by the 

 Berea and Cuyahoga shales. 



The Logan group, as classified by Orton, consists of three 

 members — a conglomerate, sandstone, and shale — and has a 

 maximum thickness of 350 feet. 1 Quite recently, however, Pro- 

 fessor Prosser has considered the question, and he divides the 

 group as follows : 2 



2. Logan formation = Logan sandstone and shales. 

 1 . Black Hand Formation = Logan conglomerate. 



Recent work by the drill demonstrates that the maximum thick- 

 ness is twice that stated by Orton. The group is limited above 

 by the Lower Carboniferous limestone, but this is rarely recog- 

 nized in deep wells, and consequently the upper limit is usually 

 uncertain. The first member of the group that is recognized by 

 the driller is the Salt sand. The relation stratigraphically of this 

 member to the Lower Carboniferous limestone is shown by the 

 following record of a well on the Longshore farm in section 15 

 of Brush Creek township, Muskingum county. All measure- 

 ments were made with a steel line. 



1 Ibid., Vol. VII, pp. 4, 5, 32-5. 2 Jour. Geol., Vol. IX, pp. 205-31. 



