GEOLOGY OF SARATOGA SPRINGS AND VICINITY 1 37 



extended southward up the Champlain trough, and westward up 

 the St Lawrence trough. 



The currents which transported these coarse sands and gravels 

 must have been vigorous ones, suggesting rather strong rehef of 

 the land which lay to the south and west. All fine material was 

 washed and blown to a distance. 



The sands of the Potsdam are succeeded by the alternating sands 

 and dolomites of the Theresa formation without any sign of a 

 break Detween them. Erosion had lowered the bordering lands. 

 Sand came down only intermittently and in less volume, and beds 

 of dolomite began to be deposited. The sands steadily diminish 

 in frequency and thickness, and thus the Theresa formation grades 

 upward into the Little Falls dolomite. Both these formations are 

 marine, but in both of them fossils are very rare, especially in 

 the dolomite. The great reefs of Cryptozoon, which occur at 

 many horizons, seem to indicate the likelihood of abundant life and 

 to suggest that the scarcity of fossils is more likely due to un- 

 favorable conditions for preservation than to their absence in the 

 marine waters. 



The Hoyt limestone is a local upper phase of the Theresa for- 

 mation about Saratoga. It seems to represent a more offshore 

 phase of the formation, and fossils are much more abundant than 

 in the ordinary Theresa or the Little Falls dolomite. This may 

 in part be due to the offshore character of the Hoyt, but it also 

 suggests more favorable conditions of preservation. 



These three formations are of extreme upper Cambric age (Ul- 

 rich would class them as Ozarkic), and are the only Cambric de- 

 posits that were laid down along the Champlain trough. Following 

 their deposit mild uplift occurred and the troughs came above sea 

 level, existed as land for a space, and w^ere somewhat eroded. This 

 erosion gently bevelled off the surface instead of deeply cutting 

 into it. which suggests that the land was of low altitude. 



ORDOVICIC HISTORY 



The uplift just mentioned forms for the geologist the dividing 

 plane between the New York Cambric formations and those classed 

 as of Ordovicic age. No one has any clear idea in regard to the 

 length of elapsed time which this uplift represents. Eventually 

 the troughs became again depressed and occupied by marine waters ; 

 and in these, on all four sides of the Adirondack region, the various 



