MONONGAHELA FORMATION 45 



in West Virginia the change is slight, but the decrease is notable toward 

 the west, for in Ohio the interval becomes little more than half that 

 north from Pittsburg. 



In the Monongahela the greatest thickness, somewhat more than 400 

 feet, is in Marion and northern Harrison of West Virginia. North- 

 wardly this decreases gradually, until in northern Washington of Penn- 

 sylvania it is but 166 feet at least 30 miles south from the line of the 

 last exposure in Allegheny coimty. There is a similar decrease east- 

 wardly, for it quickly becomes 350 feet, while in Maryland it is barely 

 250 feet. Westwardly the decrease is slow for 25 or 30 miles, but thence 

 more rapid, so that in Ohio the interval is barely 240 feet. In that state 

 there is a decrease northwardly, and at the last exposure in Jefferson 

 county it is but 140 feet, this locality being northwest from the last 

 measurement in Pennsylvania. Toward the south, southeast, and south- 

 west the story is the same. The area of deepest deposit is in southern 

 Greene and Fayette of Pennsylvania, Monongalia, Marion, eastern Wet- 

 zel, northern Harrison, Doddridge, and eastern Tyler of West Virginia. 



EAST FROM THE ALLEQHENIES 



Broad Top. — Fifty years ago Professor J. P. Lesley recognized the 

 Pittsburg coal bed in the Broad Top area of Bedford county, where it 

 remains in a tract of somewhat more than a square mile. Stevenson 

 says that it is reported 5 feet thick, but the coal has never been utilized 

 and the thickness as given is probably excessive. A limestone 12 feet 

 thick is at 200 feet above the coal, and at somewhat less than 275 feet 

 is another coal bed, belonging probably in the Dunkard formation.* 



Maryland. — Some small areas of great commercial importance remain 

 in Allegany and Garrett counties of Maryland, showing the full section; 

 others in Mineral county of West Virginia are very small and retain 

 only the lower part of the formation. The rocks throughout are tender 

 and disintegrate readily, while the sandstones are rarely thick enough 

 to affect the topography, so that sections in detail are obtained only in 

 shafts or borings. Messrs O'Harra and Martin give this succession from 

 a shaft near Frostburg, in Allegany county: 



Feet Inches 



1. Koontz [Waynesburg] coal bed 1 10 



2. Concealed 20 



3. Waynesburg limestone 5 7 



4. Sandstone and shale 31 3 



5. Uniontown coal bed 5 



6. Sandstone and shale 57 10 



•J. J. Stevenson: Bedford and Fulton counties (T 2), pp. 59, 60, 249. 

 V — Bull. Geol. Soc. Am., Vol. 18, 1906 



