498 STEVENSON— THE FORMATION OF COAL BEDS. [Nov. i, 



at several localities in the northern part of the state, but, for the 

 most part, the present outcrop is east from it as the limestone area 

 seems to follow irregularly the direction of the pre-Beaver valley 

 in which the Sharon sandstone, or latest deposit of the New River, 

 was laid down. For this reason the limestone is found nowhere 

 in Kentucky. The thickness at the north rarely exceeds 5 feet, but 

 it increases southwardly to 10 feet. The Upper Mercer is les.s 

 persistent than the Lower, but its unexpected appearance at some 

 localities suggests that its area lay farther west. Both limestones 

 are richly fossiliferous, each being at times a mass of shells. They 

 indicate ingress of the sea in a narrow area, probably nowhere 

 exceeding 50 miles in width and reaching northward to within 60 

 miles of Lake Erie along the Pennsylvania-Ohio line.^^ 



The sea again invaded the basin soon after the beginning of 

 the Allegheny, for the Putnam Hill limestone of E. B. Andrews rests 

 on the first coal bed of that formation. It did not reach into Penn- 

 sylvania but it is followed easily in Ohio from Mahoning county 

 near the Pennsylvania line to Perry county, where its character so- 

 changes that the bed is no longer available as a stratigraphic guide. 

 In much of its extent, this limestone is associated with flint and iron 

 ore and it shows great variation in thickness as well as in composi- 

 tion. Beyond Perry county, its area of deposit lay west from the 

 outcrop and only the iron ore remains to mark its horizon. It 

 carries an abundant marine fauna at most localities. At not far 

 from the Putnam Hill horizon one finds the Kanawha Black Flint 

 which occupies a small area on both sides of the Kanawha River in 

 West Virginia toward the southeastern outcrop. The probabilities 

 are, according to the plant remains, that it belongs lower in the 

 column. This black calcareous rock is embedded in black shale and 

 the mass is rich in marine forms. The area is more than 100 miles 

 east from the eastern limit of the Putnam Hill and Mercer lime- 

 stones, so that, like the Eagle limestone, it is evidence that the sea 

 had ingress on the eastern side of the bituminous region. 



''The observations by I. C. White, Newberry, Andrews, M. C. Read, 

 Stevenson, Orton and A. A. Wright are recorded in " Carboniferous of the 

 Appalachian Basin." Bull. Geo!. Soc. Amer., Vol. 15. Pp. 66-70, 80-86, 89-91. 



