﻿68 NEW YORK STATE MUSEUM 



work is only begun we are strong in our belief that uplift of the 

 whole region preceded the Beekmantown. 



The type locality of the formation, at Potsdam, is precisely 

 midway between Clayton and Lake Champlain. If one of these 

 ends is of Potsdam, and the other of Beekmantown age, it is of 

 interest to conjecture what the age may be at the type locality. 



To the writer it has long seemed clear that the sandstone and 

 the overlying dolomite must be classed in the same period, not 

 only here on the west but everywhere in northern New York. 

 By the overlying dolomite is meant not the true Beekmantown 

 formation, but the dolomites which underlie this and which, the 

 evidence indicates, underlie it everywhere unconformably. These 

 dolomites have heretofore been classed with the Beekmantown 

 and constitute Brainard and Seely's " Division A" of that forma- 

 tion in the Champlain valley, with the underlying " passage 

 beds." But while the beds of this division grade. downward into 

 the Potsdam they are separated by an unconformity from the 

 beds of " Division B " just above, as recently shown by Ulrich; be- 

 cause of which the writer has recently argued that, since this 

 unconformity is everywhere present in New York, marking the 

 emergence of the entire region, it forms the logical plane of 

 division between the Ordovicic and the group beneath. If this 

 contention be well founded, the Potsdam and Theresa formations, 

 the Little Falls dolomite, and " Division A," fall into the upper 

 Cambric group of present classifications. Ulrich has, however, 

 recently proposed a different classification, involving the in- 

 sertion of a new group of period rank between the Cambric and 

 Ordovicic, for which he proposes the name " Ozarkic," and into 

 which the Potsdam and Theresa formations would fall. For 

 many reasons the writer is in accord with this suggested innovation. 



Pamelia formation 



In our district here the Theresa formation is everywhere over- 

 laid by the limestone group here called the Pamelia formation. 

 This is in some respects the most interesting formation in the 

 section since it represents the thinned, shoreward edge of a 

 formation which, while widepread elsewhere, has not hereto- 

 fore been recognized in New York, and is in existence as a sur- 

 face formation in the State only in this immediate area. Be- 

 cause of its wide separation from other areas where the forma- 

 tion appears, and because it represents only a local facies of the 



