92 POTTSVILLE FAUNA OF OHIO 



UPPER MERCER MEMBER 

 Historical Review 



The name Upper Mercer was first given to the marine limestone, 

 which occurs above the Lower Mercer, by I. C. White in 1878 in his 

 report on Mercer County, Pennsylvania, 1 although the same stratum 

 had been previously recognized by H. D. Rogers along the Mahoning 

 River and had been named the Mahoning limestone. 2 In Mercer 

 County, Pennsylvania, the two Mercer limestones are reported to be 

 seldom exposed in the same locality. In Ohio the stratum was re- 

 ferred to by Read, Andrews, Newberry, and Orton in the State Survey 

 reports of various counties. 3 However, in 1878 the term Gore limestone 

 was applied by Dr. Edward Orton in his description of the Hanging 

 Rock District, probably from the town, Gore, in the northeastern part 

 of Hocking County. He describes the deposit thus: 4 "The Gore lime- 

 stone which is found 'from thirty to forty feet above the Zoar, resembles 

 the latter in some of its phases, and can easily be mistaken for it. Like 

 the latter, too, it is underlain with a coal seam and overlain with an 

 iron ore. As a limestone it is chiefly found in Hocking and Vinton 

 counties. It is often replaced by flint, though seldom by as heavy 

 deposits as the Zoar horizon shows. Like that limestone, it is dark 

 blue in color, but it is not as heavily charged with fossils as the Zoar." 

 In 1884 Dr. Edward Orton adopted the name Upper Mercer for the 

 Gore limestone from the equivalent stratum in Pennsylvania, 5 and this 

 term has been used in all later reports. 



Stratigraphy and Extent 



The Upper Mercer member forms the next fossiliferous horizon of 

 the Pottsville formation above the Sand Block ore, and is the fourth 

 marine limestone of the Pennsylvanian system. In Ohio its area of out- 

 crop is as great as that of the Lower Mercer limestone although it is 

 by no means as persistent or as uniform in lithologic character. It is 

 found at intervals along the entire outcrop of the Pottsville formation, 

 including the following counties, Lawrence, Scioto, Jackson, Vinton, 

 Athens, Hocking, Perry, Muskingum, Licking, Coshocton, Tuscarawas, 

 Wayne, Holmes, Stark, Portage, Summit, Mahoning, and Columbiana. 



White, I. C., Second Geol. Surv. Pa., Rept. Prog., Geol. Mercer Co., p. 36, 1878. 



2 Rogers, H. D., Geol. Pa., Vol. II, Pt. 1, p. 489, 1858. 



3 Read, M. C., Geol. Surv. Ohio, Vol. Ill, p. 567, Rept. on Coshocton County, 1878. 



Andrews, E. B., Idem., pp. 823-825, Repts. on Perry and Muskingum counties. 



Newberry, J. S., Idem., p. 795, Rept. on Mahoning County. 



Orton, Edward, Idem., pp. 898-903, Rept. on the Hanging Rock District. 



Orton, Edward, Idem., p. 898. 



5 Orton, Edward, Geol. Surv. Ohio, Vol. V, pp. 13, 14, 1884. 



