POSTGLACIAL FAULTS OF EASTERN NEW YORK 1 5 



the Lorraine shales and the overthrust mass of Cambric strata 

 forming the higher ground on the east of Defreestville. 



The faults are to be seen in the gutter of the road which goes 

 southeastward from the Defreestville corners and within a 

 quarter of a mile of the corners on the east side of the road. 

 The slates are here vertical and the faults coincide with the cleav- 

 age planes. The slates, of grayish hue, strike n. 26 e. The 

 glacial striae of the broken slate surface run from n. 29 e. to 

 n. 49 e. but are mainly n. 24 e. 



These faults were not measured with the closeness or accuracy 

 later employed in the study of the fractures at Troy and Copake, 

 but are essentially as indicated in the following table and diagram 



[fig- 4]. 



TABULATION OF FAULTS AT DEFREESTVILLE 



Distance from Amount cf 



starting point throw 



on the east in inches 



o ■ 5 



6 inches 1 . 00 



12 " 4-5 



8 " 25? 



24 " 4.00 



18 " 1. 00 



24 " . -75 



48 " 1 . 00 



1 1 . 67 feet 13 . 00 inches 



Within 11.67 ^ eet the downthrow equals 13 inches. This rate 

 of deformation if carried out over a belt of country 1 mile wide 

 would produce a difference of level at one end of the line as 

 regards the other equal to 493 feet. This fault zone, however, 

 appears to be a narrow one. The strike of the structures at 

 Defreestville would carry this belt to the east of the exposure in 

 Troy. The slips are close to the great fault described by Ford, 

 Walcott, and Ruedemann in which overthrusting is exhibited at 

 various places where the movement has been studied. Accord- 

 ing to Dale's map [U. S. Geol. Sur. Bui. 242, pi. 1] these post- 

 glacial faults would come within the area of Lower Cambric 



