

STRATIGRAPHY OF FOSSILIFEROUS MEMBERS 93 



The interval between the Upper and Lower Mercer members varies 

 greatly from place to place. At its southern extension in Scioto County 

 the average distance is 52 feet, while to the northward this interval 

 gradually thins. In Jackson County it averages 44 feet; 1 in Perry, 

 Muskingum, and Coshocton counties about 23 feet 5 inches, with a 

 minimum of 15 feet. 2 In northeastern Ohio, including Stark and 

 Mahoning counties, the same interval reaches 21 to 23 feet. 3 Between 

 the Upper Mercer member and the overlying Tionesta coal the inter- 

 vening distance averages 35 feet in Scioto County and 28 feet in Jack- 

 son. 4 



The Upper Mercer consists of a bluish-gray to almost black lime- 

 stone, often siliceous or markedly flinty in character, which resembles 

 the Lower Mercer both in lithologic character and composition so 

 closely that it is sometimes difficult to distinguish the two. In the 

 central part of the outcrop, including Perry, Muskingum, and Coshocton 

 counties, the horizon is characterized by massive, generally black 

 flint which to a large extent replaces the limestone; occasionally the 

 limestone is also replaced by massive sandstone in its central and 

 southern exposures. Dr. Edward Orton describes the member as fol- 

 lows: 5 "It everywhere lacks the remarkable steadiness and continuity 

 of the Lower Mercer limestone, but in all other respects it is almost 

 the exact counterpart of that well-marked stratum. It has, in the 

 main, the same chemical composition, the same color, and the other 

 physical properties, and also the same fossils. In many instances the 

 limestones can be distinguished only by their stratigraphical relations. 

 But though generally agreeing with the lower limestone, it has some 

 local peculiarities which serve to mark it for particular districts. In 

 central Ohio it is quite often a flint, constituting one of the main flint 

 horizons of the series." 



In southern Ohio, including Scioto, Lawrence, and Jackson coun- 

 ties, 6 the limestone is seldom present, but the horizon is represented 

 by the Lower Mercer iron ore, or Big Red Block ore, as it is called in 

 Scioto County. The ore is very persistent, and where both facies are 

 present, it lies directly over the limestone. Where the limestone is 

 found, it is hard, nodular, flinty, and dark in color; it is sparingly fos- 

 siliferous and the forms present are similar to those of the Lower Mercer. 

 The ore, which resembles the limestone in fossil content, is of good 

 quality and of sufficient thickness to be of economic value. It was 



J Stout, W., Geol. Surv. Ohio, Fourth Ser., Bull. 20, pp. 581, 161, 1916. 



2 Stout, W., Geol. Surv. Ohio, Fourth Ser., Bull. 21, p. 103, 1918. 



3 Lamb, G. F., Pennsylvania!! Limestones of Northeastern Ohio below the Lower 

 Kittanning Coal, Ohio Naturalist, Vol. 10, pp. 89-135, March, 1910. 



4 Stout, W., Geol. Surv. Ohio, Fourth Ser., Bull. 20, pp. 581, 161, 1916. 



5 Orton, Edward, Geol. Surv. Ohio, Vol. V, p. 15, 1884. 



6 Stout, W., Geol. Surv. Ohio, Fourth Serl, Bull. 20, pp. 160-171, 297-305, 580- 

 584, 1916. 



