POSTGLACIAL FAULTS OF EASTERN NEW YORK 21 



Green mountain belt in a region of folded, faulted, and over- 

 thrust slates ranging in age from the Lower Cambric to the 

 summit of the Lower Siluric. Many outcrops were found in 

 which postglacial faulting is to be suspected, as in the case of 

 the soft black slates in Argyle, but the weathering away of the 

 original glaciated surface has removed the evidence upon which 

 the proof of the movement depends. Over a large part of the 

 rounded slate hills of Argyle, the glacial drift has been entirely 

 removed, evidently by currents of water marginal to the receding 

 ice sheet, so that weathering has had a deep effect upon these 

 fragile slates. 



A peculiar distribution of outcrops of slate on certain hillsides 

 along the southern border of the Fort Ann quadrangle is in 

 accordance with the local, en echelon distribution of many faults, 

 but this rhythmic succession of small cliffs in groupsi on the 

 hillsides may be due to the manner of the glacial erosion, the 

 uplifted side or top of the small cliffs having the appearance of 

 an imperfect roche moutonnee the lower side of which has been 

 plucked away. These cliffs form an advancing and receding, 

 ascending and descending, series of exposures, the distribu- 

 tion of which is analogous to that of the small cliffs produced 

 by the spacing of such faults as are shown in figure 5 of this 

 paper. This class of outcrop forms deserves further investiga- 

 tion from several points of view and they can not be said at 

 present to be the result of faulting. 



From Fort Edward down the Hudson river as far as Troy 

 no postglacial faults of an undoubted character were found. 

 In the rock cut for the electric railway near the mouth of the 

 Moses kill between Fort Edward and Schuylerville, the slates 

 exhibit bright and shining slickensides near the present surface 

 of the ground attesting to slight movements along gliding 

 planes within the zone to which weathering has ordinarily pene- 

 trated and blemished polished surfaces that have not been kept 

 bright by secular or spasmodic recent motion. 



Judging from such occurrences as have so far come to light 

 in eastern New York, these postglacial faults occur sporadically, 

 dying out north and south along the strike of the Cambric and 

 Lower Siluric slate belt. From the observed relations to the 

 axes of folds at Troy, the movement in the slates appears to be 

 clearly one of overthrust in a region of already overturned and 

 faulted anticlines and synclines, an overthrust acting in the same 



