GENERAL COMPOSITE SECTION OF THE POTTSVILLE FORMATION 



IN OHIO (Continued) 



HARRISON ORE 



Stratigraphy and Extent 



The oldest fossilferous member of the Pottsville formation, the 

 Harrison ore, occurs at the base of the Pennsylvanian system and marks 

 the line of contact between that system and the underlying Mississip- 

 pian system. Although the ore is extremely patchy in its occurrence, 

 it is of comparatively wide extent and has been traced from Scioto 

 County on the south, where it is best developed in Hamilton Town- 

 ship, northward through eastern Pike, Jackson, western Vinton, 

 and Muskingum counties. It is also present in the Killbuck and 

 Walhonding valleys of Coshocton County. In thickness it varies 

 from 6 inches in Scioto County to a maximum of 4 feet in Jackson 

 County 1 ; to the northward in central Ohio it thins again, attaining a 

 thickness of 10 inches in Muskingum County. 2 



The Harrison ore is of especial interest on account of its position 

 with reference to the Mississippian-Pennsylvanian unconformity, 

 for it consists of the first materials deposited after the long period of 

 erosion at the end of Mississippian time. The ore lies directly upon 



, W., Geol. Sur. Ohio, Fourth Ser., Bull. 20, pp. 28, 481, 1916. 

 =Stout, W., Geol. Sur. Ohio, Fourth Ser., Bull. 21, p. 48, 1918. 



