140 J. L. Rich — Physiography and Glacial Geology 



determined by the outcrop of the heavy Lower Devonian 

 limestones. It is best developed at the extreme northeastern 

 end of the plateau about 12 miles west of Albanj- (fig. 1). On 

 the west it dies out as a conspicuous feature soon after cross- 

 ing Schoharie Creek. On the south it becomes gradually 

 lower and more broken until finally, after a course of 20 or 25 

 miles, it merges into the Hudson River lowland. 



The Hamilton Cuesta, as it may be called from the Hamilton 

 shales and sandstones to whose resistance it is due, is very pro- 

 nounced and may be traced continuously from the western 

 border of the Hudson River lowland, where its inface parallels 

 the Helderberg Escarpment and practically constitutes its 

 upper member, across Schoharie Yalley and westward to an 

 undetermined distance beyond Otsego Lake (fig. 1). 



The Catskill Escarpment^ representing the inface of the 

 highest of the three cuestas, rises abruptly out of the Hudson 

 Yalley to a height of over 4000 feet and marks the eastward 

 termination of the flat-lying resistant rocks which constitute 

 the mountains. It is practically a unit as far north as the 

 headwaters of Schoharie Creek (at Overlook Mountain), but 

 beyond this it splits into two distinct branches. The first, con- 

 stituting the main escarpment, continues northward parallel to 

 the Hudson Yalley for about seven miles, then turns northwest- 

 ward, in which direction it extends in nearly a straight line for 

 some 20 miles before dying out. The second branch, probably 

 representing rocks somewhat higher in the series, turns north- 

 westward from Overlook Mountain and, as a strong but maturely 

 dissected escarpment, which we may call the Central Escarp- 

 ment,* continues thence northwest in a line bowing slightly 

 southward, to a point at the headwaters of Delaware River 

 near Stamford, where it splits. The higher member turns 

 south westward, gradually decreases in height and finally dies 

 out, while the lower member continues northwestward about 

 live miles farther, to Potter Hill, then turns at right angles, 

 and extending southwesterly, forms the divide between the 

 waters of the Delaware and the Susquehanna. 



All these larger topographic features appear to be expres- 

 sions of rock character and structure, each escarpment repre- 

 senting a more resistant horizon, and trending in general in the 

 direction of the strike. 



The roughly rectangular arrangement of the escarpments 

 appears to be due to the relation of this region to the old land 

 from which, in Paleozoic times, it received its sediments. The 

 region, as already indicated, lies in the angle between the 



*Guyot, A., this Journal (3), vol. xix, pp. 429-451. On p. 432 this escarp- 

 ment is mentioned as " the central chain of all the Catskills," while the 

 northern escarpment is spoken of as the "northeast border chain." 



