FOLDS IN THE APPALACHIAN SYSTEM 287 



the Chemung River to the north of Wellsburg. Apparently it bears 

 sharply to the southwest near this point and joins the Pine Creek 

 syncline of Pennsylvania. While the connection between the Pine 

 Creek and Narrow Hill synclines has not been clearly established, 

 the rather abrupt eastward bend of the former, which follows, if they 

 are continuous, is in harmony with the sudden change in the trend 

 of the Wellsburg antichne and the Blossburg synchne on the south 

 from northeast to east. 



It appears certain that the comparatively insignilicant structural 

 features which have been described are of the same age and origin 

 as the great open folds of the northern Alleghenies. In the quadrangle 

 cornering with the Watkins Glen quadrangle on the southwest are 

 folds whose arches, if restored, would rise 2,500 feet above their 

 troughs.^ Less than twenty miles to the south of the Watkins Glen 

 quadrangle another great fold shows a crest of similar or greater 

 elevation. From theoretical considerations it would appear improba- 

 ble that the effects of the epirogenic forces which have developed 

 structures of such magnitude should terminate abruptly at the north- 

 ern edge of the highly folded belt. Instead of abrupt change from 

 highly folded to monoclinal or nearly horizontal structure, we find 

 the mountain flexures subsiding gradually into the low, gentle swells 

 which have been described. This may be illustrated by a compari- 

 son of the maximum dips exhibited by the anticlinal folds encountered 

 between South Mountain in Bradford county, Pennsylvania, and the 

 southern end of Lake Seneca. Eighteen miles south of the Watkins 

 Glen quadrangle runs the axis of the Towanda anticline between two 

 synclinal mountain ridges — Mount Pisgah and South Mountain. 

 Dips of 70° or more have been observed on the south side of this 

 anticline, but the average dip for the belt of maximum inchnation is 

 approximately 40°. The dips of the north limb of this fold are very 

 much lower than the south dips. The writer, although familiar 

 with the region, has not observed any dips which will exceed 20°, and 

 the dips in the zone of maximum inclination will probably not average 

 more than 15°. It is noteworthy that the great excess of the south 

 dip over the north dip of this fold is a characteristic common to nearly 

 all folds of the Watkins Glen quadrangle. 



I i^o//o AT'o. 9j, U. S. Geological Survey, p. 5. 



