OHIO AND VIRGINIA OUTCROPS 27 



stone or even of shale. The pebbles are usually flat, small, and of prac- 

 tically uniform size. Southward from Ross county, along the western 

 outcrop, the rock is less coarse and it ceases to be conglomerate before 

 reaching the Ohio river, where it is the upper portion of the Kentucky 

 Knobstone. The Logan rests upon the Cuyahoga shales of Orton, vary- 

 ing from 150 to 400 feet, with the Buena Vista sandstone at the base, a 

 persistent bed, identified with the Sharpsville of White and continuous 

 from the Pennsylvania line around the outcrop to the Ohio river at 

 Buena Vista. Below this is the Berea shale, regarded as the equivalent 

 of White's Orangeville, and at the base is the Berea grit, continuous from 

 lake Erie to the Ohio river, 50 to 75 feet thick, a fine sandstone at the 

 north, but somewhat argillaceous at the south. This ripple-marked 

 sandstone is thought by Professor Orton to be equivalent to the upper 

 part of White's Oil Lake group.* This rests on the Bedford shales. 

 Herrick has shown that the Logan does not extend so far northward as 

 do the Cuyahoga shales. 



The eastern outcrops in the Virginias. — Let us return to the east and fol- 

 low the outcrops southward from the Potomac river. 



Professor W. B. Rogers, in his " Reconnaissance," states that the Po- 

 cono (Vespertine) contains coal beds in Berkeley, Frederick, Shenandoah, 

 Rockingham, Augusta, Botetourt, and Montgomery counties of Virginia, 

 but he gives no details respecting the character or thickness of the rocks. 



Professor Fontaine regards the Pocono (Vespertine) of Augusta and 

 Rockingham as triple — a lower division consisting of sandstone, a middle 

 division of sandstone and shales with coal beds, and an upper division 

 consisting mostly of red shale and sandstone. He assigns to the lower 

 division about 400 feet of sandstone, gray below and white above. No 

 estimate of thickness of the higher divisions was made, as exposures are 

 imperfect and the region very seriously disturbed.f Mr Darton for the 

 same region, as well as a part of Pendleton county of West Virginia, 

 assigns to the lower division 300 feet of white or buff quartzite, some- 

 times slightly conglomerate. His upper division — sandstones, shales, 

 and coal beds — has an extreme thickness of 450 feet. It shows no shales 

 on North mountain, or on Shenandoah mountain along the West Virginia 

 boundary. Farther north on the latter mountain the whole thickness is 

 about 700 feet.J 



Messrs Taff and Brooks find little more than 100 feet of Pocono in 

 Randolph county, West Virginia, nearly 30 miles west from Shenandoah 

 mountain. § 



* E. Orton : Ohio Survey Reports, vol. vii, 1893, p. 28 et seq. 



t W. M. Fontaine: Am. Jour. Sci., vol. xiii, p. 116 et seq. 



I N. H. Darton : Staunton folio, U. S. Geological Survey, 1894. 



g J. A. Taff and A. H. Brooks: Buchhannon folio, U. S. Geological Survey, 1896. 



