138 NEW YORK STATE MUSEUM 



dolomite and limestone formations of the Beekniantown group were 

 laid down. These are thickest and most complete in the Champlain 

 trough which sagged more, and for a longer time, than the troughs 

 on the other three sides of the Adirondacks. But the Beekman- 

 town deposits of the Champlain trough do not occur in the Sara- I 

 toga region, and hence do not especially concern us in this report. j 

 The Saratoga district is on the western margin of the trough, its ; 

 axis lying to the eastward. The trough was submerged and i 

 emerged several times. The waters of some of the submergences 

 overspread the Saratoga region, as in the case of the Little Falls 

 submergence; but the others failed to reach the district. Appar- 

 ently the Beekmantown waters fell just short of covering it. It is i 

 barely possible that the formation was thinly deposited and sub- i 

 sequently entirely worn away. Beekmantown rocks do not appear 

 in the Saratoga section. 



Emergence of all troughs followed the Beekmantown, the emer- 

 gence being of unknown duration. Then the Champlain trough 

 was depressed so that its northern portion passed below sea level 1 

 and the marine limestones of the Chazy group were laid down. 

 This depression seems not to have reached within 75 miles of the 

 Saratoga region which remained persistently as an area of lowland 

 throughout Beekmantown and Chazy time. 



BLACK RIVER HISTORY 



Apparently emergence of all troughs followed upon the Chazy 

 depression. Because the immediate Saratoga region lacks deposits 

 of Beekmantown and Chazy age, these episodes have been de- 

 scribed as though each consisted of a single submergence and 

 emergence. In reality minor oscillations of level took place within 

 both groups. Depression of the troughs, in which the various 

 formations of the Black River group were laid down, succeeded 

 the Chazy emergence. In order of age the three chief formations 

 of the Black River group are the Lowville, the Watertown, and 

 the Amsterdam. Only the near shore edges of these formations 

 are now exposed to view in New York. They are very patchy 

 in distribution and were deposited along the oscillating margins 

 of the troughs, now above sea level, now below. The thicker 

 deposits of the central portions of the troughs are not shown in 

 surface exposures today, but lie farther away from the Adiron- 

 dacks, buried under a cover of later rocks. 



