44 J. J. STEVENSON — LOWER CARBONIFEROUS, APPALACHIAN BASIN 



is present in southern Pennsylvania and northern West Virginia ; it is 

 recognizable at more than one localit}^ along the northern outcrop, while 

 along the eastern outcrop a conglomerate often occurs at about the 

 same horizon. At the east this is above the Catskill ; in western Penn- 

 sylvania it rests on the Chemung. 



The Catskill of Vanuxem, consisting of blood-red shales and green to 

 red sandstones, was deposited in a narrow trough very deep at the east 

 and shallowing rapidly westward. In southern Pennsylvania the thick- 

 ness is 3,700 feet in Fulton county; 1,980 feet in western Bedford, 35 

 miles away ; 10 feet in western Somerset, 35 miles farther west, and 

 nothing in eastern Fayette, 5 miles farther, where the bottom conglomer- 

 ate of the Pocono (White's Cussewago) rests directly on the equivalent 

 of the Riceville shales. Nowhere in western Pennsylvania is there any 

 deposit answering to the enormous mass of Catskill found on the 

 Alleghanies and eastward. The lowest portion of Dr White's Crawford 

 County Pocono is evident^ equivalent to some portion of the transition 

 beds of eastern Penns3dvania. Whether or not any portion of this should 

 be included in the Catskill can not be determined now. 



The conditions to which the red beds were due began in New York, 

 within the Catskill region, toward the close of the Hamilton. During 

 the Chemung the influence of these conditions extended westwardly, 

 and especially south westwardly, spreading red rocks over constantly in- 

 creasing area, until rocks of that type covered the whole region of the 

 eastern outcrops in Pennsylvania, Maryland, and Virginia to beyond the 

 New river. The conditions were fatal to most forms of animal life, so 

 that we find the fauna surviving for a longer period the farther it was 

 away from the Catskill Mountain area. Occasionally, when the condi- 

 tions were interrupted, the fauna found its way, at one horizon at least, 

 into the Catskill region itself, near which Professor Prosser found it in 

 the Delaware flags. 



In New York the t3'pical Chemung fauna was cut ojff b}^ the Catskill 

 conditions, while farther west it disappeared with the narrowing of the 

 trough of sedimentation following the deposit of the Riceville and Erie 

 shales. Whether or not there was any sedimentation in Ohio during 

 the Catskill is very uncertain, but the fauna survived somewhere in the 

 northwest portion of the basin and underwent changes during that long 

 period; so that when the Cuyahoga sedimentation occurred in Ohio and 

 northwest Pennsylvania the fauna spread eastward, no longer specific- 

 ally identical with the old Chemung fauna, but related to it and retain- 

 ing the Devonian facies. 



With the next great change in topographical conditions, that intro- 

 ducing the Mississippian, this fauna disappeared and another took its 



