SIXTH REPORT OF THE DIRECTOR IO/X) 113 



The thickness of the beds that may lie beneath the bottom of 

 the Highland Park section and the top of the Hoyt limestone mem- 

 ber in the Hoyt quarry, in other words the thickness of the beds 

 belonging between the base of the former section and the top of 

 the latter, is much less certain, but so far as can be judged from 

 sections elsewhere the amount is not great. Estimating the Hoyt at 

 a maximum of ioo feet and the upper member at about 150 feet, 

 the total thickness of the Little Falls formation in the vicinity of 

 Saratoga may be set down as approximately 250 feet. The maxi- 

 mum may fall a trifle under this figure, but it is quite certain that 

 it does not exceed 300 feet. Locally, however, on account of Pre- 

 mohawkian erosion the thickness may be considerably less. 



At Rock City Falls, 7 miles west of Saratoga, contact with the 

 Mohawkian is well exposed. Here this Ordovicic limestone rests 

 upon darker colored dolomites of the Little Falls formation which 

 seem to belong beneath the coarse, whitish rocks of the upper por- 

 tion. Midway between Saratoga and Rock City Falls are other 

 exposures which show Mohawkian limestone resting on similar 

 beds, though the higher, coarse grained, whitish beds are near at 

 hand, and in such situation that we can only interpret the exposures 

 as indicating that the Mohawkian was deposited on an eroded sur- 

 face of the Little Falls dolomite, beds being absent in some sec- 

 tions both above and beneath the unconformable line of contact 

 that are present in others. The evidence seems clear to us that 

 the whitish summit beds of the Little Falls have been eroded away 

 locally, the Mohawkian in such cases resting on lower beds. 



The lower part of the Mohawkian varies greatly within and in 

 areas adjacent to the Saratoga quadrangle. As a rule the basal 

 Mohawkian beds in this region have been assigned to the Trenton, 

 but, so far as observed, they are in all cases older than the low- 

 est Trenton in the type sections on West Canada creek. At the 

 same time, however, the first Ordovicic bed to follow the Little 

 Falls dolomite, or the Tribes Hill formation and the thin irregular 

 wedge of Lowville where these are present, is younger than the 

 Watertown limestone (" 7 foot tier") of the Black River group. 

 In other words, in the area between Saratoga on the east and say 

 Canajoharie on the west, the post-Lowville Mohawkian begins with 

 beds that are wanting along West Canada creek and Black river. 

 At Saratoga a 6-10 foot, heavy bedded crystalline limestone is 

 found either resting on or not more than 5 feet above the top of the 

 Little Falls dolomite. At Rock City Falls, 6 miles west, this bed 



