130 POTTSVILLE FAUNA OF OHIO 



BLACK FLINT MEMBER 

 Stratigraphy and Extent 



The Black Flint member, which forms the next fossiliferous hori- 

 zon above the McArthur limestone, is near the top of the Pottsville 

 formation. It is a very local deposit and its outcrop is confined to 

 Jackson and southwestern Vinton counties. 1 The member is associated 

 with the basal member of the Allegheny formation, namely the Brook- 

 ville coal, which it either directly underlies or from which it is separated 

 by a few feet of clay and shale; however, the coal is much more per- 

 sistent than the flint. The interval between the Black Flint and the 

 Tionesta coal with its accompanying McArthur member varies from 10 

 to 35 feet with an average of 21 feet. In Jackson County, Washington 

 Township, the entire thickness of the Pottsville formation from the 

 Sharon conglomerate at the base to the Black Flint was measured in 

 Section 21 from the old Glen Nell mine to the hill just west of the Town 

 House and was found to be 273 feet. 2 



The Black Flint horizon is marked by deposits of extremely hard, 

 lustrous, black flint; impure, very fossiliferous limestone; and nodular 

 iron ore. In the southern part of Jackson County heavy beds of sand- 

 stone mark the top of the Pottsville formation; northward in Lick 

 Township, east of Jackson, the member is represented by fairly per- 

 sistent iron ore, 5 to 15 feet below the Brookville coal. When only one 

 bench is represented, the thickness is about 6 to 8 inches, although 

 three benches, each 4 to 6 inches thick, may be present. Fossils are 

 absent or are found very sparingly. The ore was formerly used for 

 smelting in the old charcoal furnaces of the vicinity. 



In the northeastern part of Jackson County, including Coal and 

 northern Milton townships, the flint and ore are both present in patches 

 although they are seldom found together. The flint is deep black, 

 lustrous, and about a foot in thickness; in the latter township it is 

 underlain by shaly, gray limestone which contains a great abundance 

 of fossils in an excellent state of preservation. The ore on the horizon 

 measures 8 inches in thickness. In Washington Township only flint 

 and gray limestone are present. 



As the flint passes northward into Vinton County it thickens some- 

 what and is found in Richland, Clinton, and Elk townships where both 

 ore and flint are present. The thickness of the ore is about 8 inches 

 while that of the flint varies from 1 to 2 feet. In central Richland 

 Township the flint and gray limestones are exposed on the high knobs, 

 while in western Clinton Township, east of Hamden, they are found at 

 the tops of some of the hills. The northern limit of the deposit is in 



iStout, W., Geol. Surv. Ohio, Fourth Ser., Bull. 20, pp. 179-187, 1916. 

 2 Idem., p. 183. 



