GEOLOGY OF SARATOGA SPRINGS AND VICINITY 7 



Hudson trough. This is not a mere valley of erosion but a true 

 trough, having been repeatedly depressed as compared with the 

 districts east and west of it. Erosion has had its part in the 

 development of the valley, but as a secondary instead of a primary 

 factor. In the mapped district this lowland is seen merging into 

 the Mohawk lowland. Across the Hudson, along the east margin 

 of the Schuylerville sheet, rises a range of hills, the outlying 

 western rampart of the New England plateaus. 



Turning from topography to geology we find the old crystalline 

 rocrks of the Adirondacks coming into the district from the north. 

 These are margined by the flat-lying sandstones, limestones and 

 shales of early Paleozoic age which were deposited in the Cham- 

 plain basin, even in that early time a sinking trough. These in 

 turn are adjoined on the east by the series of much disturbed 

 shales of the Hudson valley, a quite different series of rocks from 

 those of the Champlain basin. They were deposited, also in early 

 Paleozoic times, in a wholly separate and more easterly trough 

 than the Champlain basin, and have been brought to their present 

 location by being thrust over to the west by the action of great 

 compressive forces. As rocks they are not indigenous to the 

 region, but exotic. Still farther east come the limestones and impure 

 shaly rocks of the Bald ^Mountain ridge, also overthrust into the 

 district from the east. These rocks are so different from those 

 of the Champlain basin that we are of necessity constrained to 

 describe and discuss them in separate chapters. 



In two minor features the geology of the region is unique. One 

 of the Paleozoic formations of the Champlain basin, the fossil- 

 iferous. Upper Cambric limestone which was first described by 

 Walcott, occurs as a surface formation in Xew York only in the 

 immediate vicinity of Saratoga.^ Just north of Schuylerville there 

 outcrops a knob of extrusive igneous rock, first recognized and 

 described by Woodworth. which is unlike any other known igneous 

 rock of the State, and which has been made to play a part in one 

 theory of the origin of the spring waters. - 



^ U. S. Geol. Surv.. Bui. 30, p. 21-22. 



2 N. '\'. .State riool. 2r.st .\nn. Rcp't. p. ri7-r29. icjoi. 



