in the Cayuga Lake Region. 239 



45°, however, may be modified and greatly reduced by a 

 number of conditions. Two in particular apply to the 

 case in hand. As brought out in the article on Low- Angle 

 Faulting, 1. to lower the angle of the fault plane means, 

 to decrease resistance by friction as produced by normal 

 compressive stress ; hence the avenue of least resistance 

 will be taken. 2. "Rotational strain may be developed 

 from horizontal compressive stresses, in heterogeneous 

 material by bedding or similar structure, which present 

 differences in competency. ' ' 6 



Deductions. 



From the above facts as shown by the faults of the 

 Encrinal layer of the Cayuga Lake region it may be 

 assumed that the forces which produced them worked 

 approximately horizontally and came from a direction 

 between 4° and 15° west of south. This is a rather sur- 

 prising development in view of the preceding statement 

 that the region belonged to the outskirts of the Appalach- 

 ian province and had shared its history even though in 

 less active form than the mountainous tract. Some inti- 

 mation of the fact might have been discerned in the pro- 

 gressively changing curve of the axes of the anticlines as 

 shown in folio No. 169 page 100 as they turn from a gen- 

 eral SSW-NNE to an easterly direction. So ingrained, 

 however, is the idea that all pressure as applied to the 

 Appalachians must come from the southeast that the 

 warning passed unnoticed. 



In northwestern central Pennsylvania, as well shown 

 on the IT. S. topographic map, there occurs a sharp turn in 

 the trend of the Appalachians, with convexity N-W, 

 swingings them across northern Pennsylvania and south- 

 central New York in a nearly east-west course. This 

 soon again turns and they pass northward through New 

 England in the usual NNE direction. Lines drawn at 

 right angles to the trend of the second curve which occurs 

 in south-eastern New York would converge not far east of 

 Cayuga Lake, which means that this region is practically 

 due north of the east-west segment. The fact that the 

 axis of the Portland Pt. anticline crosses Cayuga Lake 



6 Chamberlin, E. T. and Miller, W. Z., Low-Angle Faulting, Jour. Geol., 

 vol. 26, p. 44, 1918. 



