CHAPTER VI. 



STRATIGRAPHY THE MONONGAHELA 

 SERIES. 



GENERAL DESCRIPTION AND SECTION. 



The Monongahela Series of the Pennsylvania!! Rocks, 

 first named and described by H. D. Rogers from its abundant 

 c i tcrop along the Monongahela River in the State of Penn- 

 sylvania, and later described in more detail by Jno. J. Steven- 

 son, I. C. White, and others, includes a large portion of the 

 outcropping rocks of Lewis and Gilmer. Portions of it are 

 found in every magisterial district. Along the northwestern 

 edge of the two counties, it goes under drainage and in the 

 southern end of Lewis, in portions of Skin Creek and Col- 

 lins Settlement Districts, the southeastward rise of the rocks 

 elevates it above the hilltops, but between these limits its out- 

 crop is continuous. 



In Lewis and Gilmer the series consists mainly of sand- 

 stone beds, greenish or gray in color, alternating with red or 

 sandy shales, and contains two important coal seams as well 

 as some that are not of commercial rank. The abundant lime- 

 stone horizons of northern West Virginia and western Penn- 

 sylvania are almost wholly lacking, being represented by only 

 one stratum of importance. Three important coal beds, the 

 Waynesburg, Uniontown, and Sewickley, that are of minable 

 thickness elsewhere, are too thin in Lewis and Gilmer to have 

 commercial importance. Taken as a whole, the series lacks 

 many of the economic features found in the more northern 

 counties, while its thickness remains essentially the same, hav- 

 ing a larger percentage of sandstone and red beds. 



The following general section, compiled from the detailed 

 sections of Chapter IV, and from numerous special observa- 



