GEOLOGY OF SARATOGA SPRINGS AND VICINITY 5 1 



As a rule, one meets only Corynoides calicularis and 

 Lasiograptus eucharis, the two most common fossils, as 

 at the Glowegee and the upper branches of the Snook kill. At 

 the Gansevoort fall, however, also Glossograptus quadri- 

 mucronatus mut. cor nut us, a characteristic form of an 

 upper horizon of the Canajoharie shale was obtained in typical 

 specimens. 



Correlation. We have shown in another paper,^ that the Cana- 

 joharie is of lower Trenton' age and essentially contemporaneous 

 with the Snake Hill shale. The two have, therefore, some import- 

 ant horizon markers, especially graptolites, in common. While, 

 however, the Snake Hill shale rests on either upper Normanskill 

 shale or Rysedorph Hill conglomerate and belongs to a vertical 

 series that begins with the Georgian beds at the bottom, the Cana- 

 joharie shale can be seen to rest on the basal Trenton limestone 

 at Glens Falls, the latter being underlain in turn by the Amsterdam 

 limestone. It is therefore to be inferred that although the Cana- 

 joharie and Snake Hill shales may be approximately synchronous, 

 they were formed in different basins and have come in contact 

 through later diastrophic movements (see diagram and page lOO.) 



The Canajoharie shale is equivalent to the lower part of the Mar- 

 tinsburg shale in Pennsylvania and New Jersey, with which it has 

 the characteristic fossils in common and is probably continuous 

 with it through southern New York. The Martinsburg shale, how- 

 ever, comprises also beds of Utica and Eden age. 



THE SCHENECTADY FORMATION 



In the southwestern corner of the Saratoga sheet, from Birchton 

 westward, the grits of the Schenectady formation are exposed in a 

 number of places, showing that this formation just reaches the sheet 

 from the southwest. 



The Schenectady formation consists in the lower Mohawk valley 

 of 2000 feet of grits and sandstones with interbedded black and 

 gray argillaceous shales, the two forming a monotonous, uniformly 

 alternating series throughout this great thickness. IMie sandstone 

 beds are quarried about Schenectady and Aqueduct, and in the 

 latter place, where the Alohawk river in its new postglacial course 

 breaks through a ridge of these harder beds, an excellent section of 

 a portion of the formation is furnished. These gray, im])ure sand- 

 stones and gray to black argillaceous shales have, until recently, 



' N. Y. State Miis. Bui. 162, p. 29. 



