lOO NEW YORK STATE MUSEUM 



regions the folding has transgressed a few miles into the Cana- 

 joharie shale area while in others some western marginal cakes of 

 the Snake Hill beds have been left only shattered by fault slips. 

 Thus in Albany county the Canajoharie shale belt striking along 

 the Hudson river has become, partly at least, involved in the fold- 

 ing, while on the Saratoga sheet the Snake Hill shales west of 

 Saratoga lake are only tilted and broken. The boundary between 

 the folded and unfolded areas follows thus on the Schuylerville 

 quadrangle the longer axis of Saratoga lake, being probably in 

 part responsible for the existence of this basin in that place. It 

 thence continues northwest passing west of Kendricks hill where 

 folded Snake Hill shales are exposed. The folded area may also 

 include the last outcrops of Canajoharie shale on the Snook kill 

 below Gansevoort, the shale being there in steeply eastward dip- 

 ping position. 



In general, however, the boundary of the folded and unfolded 

 regions coincides so closely with the Canajoharie-Snake Hill bound- 

 ary that the proposition of the folding and shoving of the eastern 

 series of shales upon and against the western is well supported by 

 this fact. The crumpling up of a narrow belt of Canajoharie shale 

 in front of the folded area in Albany county on one hand and the 

 shoving westward of a cake of Snake Hill beds without folding 

 (but with much slipping, see below page 103) in Saratoga county 

 on the other hand, both result from the varying resistance offered 

 the oncoming waves of pressure and of folds from the east, 

 through the thickness of the opposing strata and the weight of 

 their covering formations. It appears from the fact that some 

 of the outcrops on the southeast shore of Saratoga lake (on the 

 Cohoes quadrangle) show a great number of closely arranged 

 thrust planes, all rising slightly to the west, that the pushing force 

 in this more or less unfolded western cake was largely spent in 

 overthrusting, this action taking place near the surface under little 

 or no cover. 



We have shown before that the Canajoharie and Snake Hill 

 beds belong to different series of rocks, deposited in different 

 basins. Of these the Canajoharie shale's have changed their posi- 

 tion on the whole only vertically through normal faulting, while 

 the folded shales must have been transported for some distance 

 subhorizontally to come to lie in contact with and partly above 

 the western series. This transportation took place both by 

 folding and overthrust faulting. There is little doubt that the 



