COMPARISON OF SECTIONS 



171 



in the Chazy section by the dove reef limestone at the base of the upper 

 Chazy."i« 



Comparison with the Champlain and Mohawk Sections 



Champlain valley. 



Mohawk valley. 



^Vatertown district. 



Black River and Lowville, 40 to 

 60 feet. 



r Black River, to 15 feet. 

 I Lowville, to 25 feet. 



Black River, 20 feet. 

 Lowville, 60 to 75 feet. 



f Upper, 200 feet 



Absent 



Absent. 







Pamelia, 40 to 140 feet. 



^nazy -; j^jj^^jig^ ggg feet 



Absent 



Absent. 



L Lower, 340 " 



Absent 



Absent. 









C Division E, 470 feet. 



Beekman- J Division D, 375 " . 



town. 1 Division C, 350 " . 



Division B, 295 " . 



[ Absent 



Absent. 







Beekmantown, A, 310 feet. 

 Passage beds, 30 to 75 " 



Little Falls dolomite, 

 500 (?) feet. 



Unconformity. 



1 Theresa, 20 to 60 feet. 



Potsdam 



Absent 



Potsdam . 









The above correlation table is a modification of a more extensive table 

 sent me by Ulrich as representing his views. We are in agreement in 

 everything excepting perhaps the age of the Little Falls dolomite of the 

 Mohawk valley, which is tabulated in accordance with my view instead 

 of his. The determination of the age of the Pamelia formation and the 

 recognition of the unconformity in the Champlain-Beekmantown are 

 wholly Ulrich's. 



In the Champlain valley sedimentation was in bulk and was compara- 

 tively uninterrupted during the Upper Cambric and Lower Siluric, ex- 

 cept for the unconformity previously noted, and the deposits shown there 

 today were laid down somewhat more removed from the margin of the 

 subsiding basin than was the case in the Mohawk and Watertown dis- 

 tricts, where the deposits w^ere marginal, hence thin and more interrupted 

 by breaks produced by oscillations of level. With the oncoming of Black 

 Eiver deposition we find for the first time evidence of connecting seas 

 on all four sides of the Adirondack region, thus initiating the great 

 depression of the succeeding Trenton and Utica epochs, when New York 



■ Ulrlch : Lettei- of March 25, 1908. 



XVII — Bull. Geol. Soc. Am., Vol. 19, 1907 



