280 CAMPBELL NORTH PENNSYLVANIA AND SOUTH NEW YORK 



In the region mentioned this surface may be observed in the south- 

 east corner of the Tioga quadrangle, in the vicinity of Mansfield, at an 

 altitude of about 1,600 feet. In the northeast corner of the same quad- 

 rangle it rises to about 1,800 feet. In passing westward it is found at an 

 altitude of 1,800 or 1,900 feet in the northern part of the Elkland quad- 

 rangle, and still farther west it rises to an altitude of 2,100 or 2,200 feet 

 in the northern part of the Gaines quadrangle on the New York state 

 line. Part of this increase in altitude toward the west may be due to 

 the greater distance from the main drainage lines, but evidence pre- 

 sented later makes it seem probable that all of the surface features of this 

 region show a similar rise toward the west, and that it is largely due to 

 crustal movements. 



The area under discussion is crossed by a broad synclinal trough, 

 which extends from the southwest corner of the Gaines quadrangle to 

 the middle of the eastern side of the Tioga quadrangle. Although 

 breached by streams in many places, this is a fairl}^ continuous ridge, 

 which rises 400 or 500 feet above the Chemung uplands on the adjacent 

 anticlinal tracts. The general altitude of this ridge ut the eastern mar- 

 gin of the territor}^ is about 2,200 feet. It rises gradually westward to 

 2,300 feet on the western margin of the Elkland quadrangle and 2,400 

 or 2,500 feet on the western edge of the Gaines quadrangle. In the cen- 

 ter of this trough the rocks are nearly horizontal, and the resulting 

 topograph}^ is characterized by broad and flat-topped summits. If the 

 ridge throughout this territory were capped continuously by the heavy 

 Pottsville conglomerate, such flat tops would not be surprising ; but the 

 synclinal trough consists of a series of connected basins, in which the 

 Pottsville rocks are preserved, but between which the surface of the 

 ridge is composed only of the thin-bedded Catskill-Pocono rocks. In 

 their resistance to erosion these beds bear no comparison to the massive 

 Pottsville sandstones, but despite this diff'erence the surface of the ridge 

 where they outcrop is practically at the same elevation as in the locali- 

 ties where it is composed of the Pottsville sandstone. For this reason 

 it seems probable that the summit of this ridge is also a remnant of a 

 peneplain which is much older than that at the level of the hilltops on 

 the adjacent anticlinal tracts. 



Although remnants of two peneplains may be easily distinguished in 

 this region, the determination of their dates of origin is a difficult ques- 

 tion. As heretofore mentioned, this general upland surface has been 

 referred to the Cretaceous peneplain ; but from the foregoing facts it is 

 apparent that the surface features are not so simple as has been sup- 

 posed, and consequently there may be two peneplains to account for 

 instead of one. Since it is not possible at the present time to trace these 



