430 W. J. MILLER 



very local district. Numerous observations are not possible because 

 of the heavy drift covered areas, but, as far as can be ascertained, 

 these highly folded layers are visible only in the Trenton Falls gorge 

 and in the bed of Cincinnati creek, one and one-half miles southv^^est 

 of Prospect. Along Mill creek, near Gravesville, several miles to the 

 southeast, most of the Trenton section is exposed but the folded layers 

 have not been found there. 



Similar phenomena of highly folded between non-folded strata have 

 been observed in the stratified clay banks of Pleistocene age along 

 Black River to the north of Trenton Falls and also in the banks along 

 the canal feeder west of Forestport. The latter occurrence has been 

 described and figured by Vanuxem.^ 



CAUSE OF THE FOLDING^ 



Vanuxem^ states that the folded layers are more thoroughly 

 crystalline than the undisturbed layers above and below and that as 

 the material of the disturbed layers was being crystallized it caused 

 an expansion which manifested itself laterally by throwing the layers 

 into folds. However, a careful examination of the layers in the folded 

 zone and those above and below fails to show any real difference in 

 degree of crystallization. Even if such a difference in degree of 

 crystallization were present, it is difficult to see how simple crystal- 

 lization of the mass could bring about such a considerable lateral 

 expansion. 



T. G. White^ cites Professor W. O. Crosby as suggesting that the 

 folds may have been caused by the great weight of overlying strata. 

 According to this view it is extremely difficult to explain the sharp and 

 even overturned folds and the minor thrust faults which imply a 

 distinct shortening of the layers within the folded zones. 



In many places the structure of the upper folded zone greatly 

 simulates cross-bedding and the writer was at first of the opinion 

 that it, in reality, did show cross-bedding. The close association, in 

 the same zone, of truly folded and broken strata soon caused this idea 



I Op. cit., pp. 214, 215. 



•2 The writer here wishes to express his thanks to Dr. C. K. Swartz of the Johns 

 Hopkins University for suggestions regarding the cause of the folding. 



3 Loc. cit., p. 90. 



4 Op. cit., pp. 88-90. 



