274 



GEORGE C MATSON 



miles south of the Watkins Glen quadrangle runs the axis of the Towanda anti- 

 cline between two synclinal mountain ridges — Mount Pisgah and South Moun- 

 tain. Dips of 70 or more have been observed on the south side of this anticline, 

 but the average dip for the belt of maximum inclination 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. 1 



Accompanying the folding were movements along the bedding 

 planes; some minor thrust faults were formed. These two forms 

 of displacement pass into each other. Willis discusses the con- 

 ditions under which displacements along bedding planes take place, 

 in his article on "The Mechanics of Appalachian Structure:" 



The transmission of pressure through a folding stratified mass may be stated 

 as follows: So long as the stratification is parallel to the original direction of 

 pressure, the force is transmitted as a whole and tends to reduce the volume of 

 the mass; when the strata are inclined to the direction of pressure, the thrust is 

 resolved into two components, the one. parallel to the bedding, the other perpen- 

 dicular to it; the former produces movement when it overcomes the friction on the 

 bedding planes, the viscosity of the strata and any opposing force, as the load; 

 the latter becomes active when it causes some part of resisting mass to move. 2 



It was doubtless the thrust parallel to the bedding planes which 

 produced the displacements under discussion. Where the cohesion 

 between the strata was less than the strength of the rock, the move- 

 ment took place along the bedding planes; where the cohesion was 

 greater than the strength of the rock, a fracturing of the beds resulted, 

 and movement took place along the fracture plane. Since these 

 disp acements have a bearing on the history of the dikes, a few of 

 them will be discussed here. On the south limb of the Watkins 

 anticline, in Six-Mile Creek, is a small thrust fault which passes into 

 a displacement along the bedding planes. In Shurger's Glen there 

 is a similar fault connected with the anticline which crosses Lake 

 Cayuga near Shurger's Point. In this case the fault passes into 

 displacements along several adjacent bedding planes. On the north 



1 "A Series of Gentle Folds on the Border of the Appalachian System," Journal 

 of Geology, Vol. XII, No. 4 (1904), p. 287. 



3 Willis, Thirteenth Annual Report, TJ. S. Geological Survey, Part 2 (i89i~92> 

 p. 246. 



