GEOLOGY OF SARATOGA SPRINGS AND VICINITY 1 5 



The deposits of these terraces were laid down in close prox- 

 imity to the ice sheet, occasionally covering stranded blocks of ice. 

 When this melted away, depressions were left which became occu- 

 pied by ponds. Three such ponds lie in the sands south of Corinth ; 

 and Moreau pond, northwest of Gansevoort, and Lonely lake near 

 Saratoga lake, are larger examples. Saratoga lake itself lies in 

 an old drainage valley, and in a portion of it which was less deeply 

 filled with drift than the remainder. 



GENERAL GEOLOGY 



BY II. P. GUSHING 



The surface rocks of the Saratoga and Schuylerville quadrangles 

 belong apparently to two separate geologic provinces. The rocks 

 of the Saratoga and the western portion of the Schuylerville quad- 

 rangle are those of the Adirondack plateau and the lower Mohawk 

 trough ; those of the remainder of the Schuylerville quadrangle 

 are deposits of more eastern troughs. The Adirondack plateau 

 rocks are of Precambric age and comprise both sedimentary and 

 igneous rocks. Those of the Mohawk trough are of early 

 Paleozoic age, Cambric and Ordovicic, and contain no igneous 

 rocks in the Saratoga region. Those of the more easterly troughs 

 are also of early Paleozoic age. Cambric and Ordovicic. But the 

 formational units are quite different from those of the Mohawk 

 trough, and the two are also very unlike structurally. 



Except for the cover of comparatively recent deposits of 

 Pleistocene age there are no rocks in the region younger than the 

 Ordovicic, with one trifling exception, and that an igneous rock. 

 A mile north of Schuylerville, on the west bank of the Hudson, 

 is a small knob of extrusive rock of peculiar character, which is 

 certainly younger than the Ordovicic and in all probability very 

 much younger. 



STRUCTURE 



Since their formation the rocks of the Adirondack region and 

 the Mohawk trough have been considerably deformed. The 

 Precambric rocks of the Adirondacks. were enormously deformed 

 in Precambric time and folded in a complex manner, while the 

 sediments were all cut to pieces by great intrusions of igneous rock 

 from beneath. 



Besides this early deformation the rocks of the eastern Adiron- 

 dacks have undergone subsequent deformation, in common with 



