FOLDED BETWEEN NON-FOLDED STRATA 431 



to be cast aside. White' gives photographs showing supposed over- 

 lap structure and channel filling. These structures appear to be 

 merely parts of the disturbed zones, described in this paper, where the 

 beds have been broken or only gently folded. 



It has occurred to the writer that the phenomenon might have been 

 due to a lateral compression within the region, which caused most of 

 the hmestone beds to become denser without being greatly folded, 

 while certain other layers yielded to the compressive force by folding. 

 Such an explanation would imply a difference in texture between the 

 folded and non-folded strata, but such a difference is not noticeable. 

 Also it would seem to assume that the folded zone was more rigid 

 while the evidence appears to indicate, if anything, that it was less 

 rigid. 



It is thought that the folded structure at Trenton Falls was in 

 reality caused by a differential movement within the mass of the 

 Trenton Hmestone, That the whole body of the limestone has been 

 moved is clearly demonstrated by the existence of a thrust fault, of 

 considerable throw, passing Prospect village. The displacement 

 was sufficient to cause beds of the middle Trenton to sHde over beds 

 of the upper Trenton, Near the fault-plane the beds on the upthrow 

 side are bent upward at angles of from thirty to forty degrees. The 

 following figure, shows the relation of the fault to the folded zones. 





Fig. 2. — Section showing the position of the two folded zones in the Trenton 

 limestone and their relation to the thrust fault at Prospect, near Trenton Falls, N. Y. 



It is easy to see how when the force of compression was brought to 

 bear in the region there would be a tendency for the upper Trenton 

 beds on the upthrow side to move more easily and consequently 

 faster than the lower Trenton beds. For instance the portion A in 



I Op. cit., PL III, Fig. B, and PI. IV, Fig. B. 



