24 .T.J. STEVENSON — LOWER CARBONIFEROUS, APPALACHIAN BASIN 



ward, so that where cut by Cheat river, in Preston count}^ it brings up 

 only the topmost 50 feet of the Pocono, which is a massive sandstone- 

 About 425 feet of Pocono is above the river in its gap through Chestnut 

 ridge, in the same county. There it appears, to be wholly sandstone, 

 massive and pebbl}" at the top, where it is current-bedded, but hard and 

 flaggy below.* 



The ivestern counties of Pennsylvania. — Returning now to the northern 

 border, Mr Carll says that the Shenango (sub-Olean) is not always con- 

 glomerate in Warren county (west from Potter and north from Forest). 

 He finds at Warren the Shenango 30 feet thick, resting on 53 feet of 

 shales and sandstone, containing some fossiliferous beds, below which 

 are shales and sandstones for 363 feet. Near the same place Mr Randall 

 found 40 to 50 feet of Shenango resting on an equal thickness of buff, 

 sandy shales, succeeded by sandstones and shales, about 250 feet, to a 

 flat pebble conglomerate, which is evidentl}' the first Venango oil sand, 

 the Upper Chemung conglomerate of Stevenson. Mr Randall says that 

 the Shenango and the immediately underl3dng shales are fossiliferous, 

 and suggests that the species show a mingling of Chemung and Car- 

 boniferous forms. t Here the lower transition beds and the Catskill 

 have disappeared. 



Passing over into Crawford county, on the Ohio line, one finds Doctor 

 White's detailed studies, which make the section clear and prepare for 

 the Ohio conditions. The Shenango sandstone, the topmost portion of 

 the Pocono, is a flat pebble rock, 15 to 35 feet thick in Crawford and 

 Erie counties. It has been traced by Doctor White eastward from the 

 Ohio state line through Crawford, Warren, and McKean, and, farther 

 south, from the same line across Mercer and Clarion. It is white, always 

 sandstone, and becomes massive and coarser eastW' ard. It show^s notable 

 variations in thickness, 15 to 35 feet in Crawford, wdiile in southern 

 Mercer, near Sharon, it is only 3 to 7 feet, though always retaining its 

 character. It is pebbly near the Ohio line, but the pebbles are fine. 

 The bottom layers become pebbly at Meadville, in Crawford. At Gar- 

 land, in Warren, they are quite pebbly. At Warren, in the same count}^ 

 the rock is pebbly throughout and 40 to 50 feet thick. At many places 

 it contains fish remains. 



Doctor White's Meadville shales underlie the Shenango sandstone, 

 are 60 to 80 feet thick, and are divided above the middle b}' 6 to 18 

 inches of limestone. These shales are persistent also in Mercer and 

 Venango counties. The limestone, Upper Meadville of White, is very 



* r. C. White: Notes on the geologj' of West Virginia. Proc. Am. Pliil. Soc, vol. xx, 1882, pp. 

 488-492. 

 t J. F. Carl! : Geological report on Warren count}' (I 4), 1883, pp. 100, 298, 305. 



