REPORT OF THE DIRECTOR I914 I4I 



a little start, as along two horizons within the formation, any 

 renewed or continued movement would tend to follow the same 

 horizons. It is at least significant that the contorted zones occur 

 in the weakest portion of the Trenton formation ; that is, where the 

 soft shale partings are the most pronounced. 



Replying to the statement that tectonic contortions are pressure 

 phenomena produced under heavy loads, it may be said that, in 

 the light of comparatively recent investigations, a great overlying 

 load would not be necessary in order to permit the development of 

 folded and faulted structures such as those in the contorted zones 

 at Trenton Falls, particularly since the strata are alternating thin 

 layers of unaltered limestone and soft shale. No doubt consider- 

 ably more overlying rock was present during the folding and fault- 

 ing process than now. Distinctly stretched or flattened out masses 

 would scarcely have been produced under the pressure conditions 

 which obtained. 



In contrasting folds of the zones of fracture and flow, Leith 

 clearly states ^ that there is " little slipping between the beds " in 

 the zone of flow, while there is '' much slipping between the beds " 

 in the zone of fracture. The deformation of the strata at Trenton 

 Falls certainly took place in the zone of fracture as proved by the 

 very existence of the sharp thrust fault and the fractured character 

 of the rocks within the contorted zones. Considering also the thick 

 partings of soft shale, it is readily seen that the conditions were 

 very favorable for slipping between the beds or differential move- 

 ments of the strata. 



Hahn also emphasizes the point that slickensides should be very 

 evident according to the tectonic hypothesis. While it is true that 

 some slickensides occur within the disturbed zones, nevertheless 

 they are not very evident at either the tops or bottoms of those 

 zones. When it is remembered that the Trenton consists of alter- 

 nating soft shales and comparatively hard limestones, it is easy to 

 see how the sliding must have taken place along the bands of soft 

 shale which were more or less crushed but not notably slickensided. 

 In spite of the lack of direct evidence from slickensides, the writer 

 believes that the multitude of sharply broken limestone fragments 

 (apparently not recognized by Hahn) toward the tops and bottoms 

 of the disturbed zones, as well as within them, clearly supports the 

 view that there has been actual rubbing (sliding) of the masses of 

 the disturbed zones against both the overlying and underlying 

 masses. Even if we should grant Hahn's argument concerning lack 



1 Structural Geology, p. iii. 



