174 H. p. GUSHING PALEOZOIG IN NORTHWESTERN NEW YORK 



basal Beekmantown and Chazy sandstones in the sections, it is also likely 

 that in many places the Potsdam is also present, and that the unconform- 

 ity can be recognized there as in New York. Grabau also urges that the 

 Beekmantown of these Canadian areas represents only the upper part of 

 the formation as it exists in the Champlain valley, which view is pre- 

 cisely that urged here for the Beekmantown on the Kew York side. 



In the correlation table on a previous page the Little Falls dolomite 

 (the local name for the representative of the supposed Beekmantown of 

 the Mohawk valley) is given as the equivalent of Division A of the 

 Champlain valley and of the Theresa formation of the Watertown region. 

 It should be frankly stated at the outset that this is the element in the 

 table whose precise position and relationship is quite uncertain. This is 

 owing in part to its unfossiliferous character and in part to the fact that 

 the formation is separated by gaps from the other districts, so that it 

 can not be directly traced from one to the other. In a recent publication 

 the writer has argued that at least all the upper fossiliferous Beekman- 

 town (Divisions D and E) of the Champlain valley is absent along the 

 Mohawk.^* Ulrich's discovery of the unconformity between Divisions 

 A and B in the Champlain valley, necessitating the separation of Division 

 A from the Beekmantown formation, at once raises the question as to' 

 whether the entire Little Palls dolomite may not lie below the horizon 

 of the unconformity and hence not be Beekmantown at all, but be prop- 

 erly correlated with Division A and the Theresa formation and possibly 

 even with the Potsdam. This was at first Ulrich's view, and still seems 

 to the writer the one most in accord with the evidence as it can be gleaned 

 from the New York sections, and hence it is the one adopted in the corre- 

 lation table, though with open admission that the evidence is far from 

 conclusive. Ulrich's later and more refined studies have led him to 

 prefer a somewhat different view, though he does not regard any of the 

 formation as of Beekmantown age.-" 



There is a second doubtful matter connected with the Little Falls dolo- 

 mite, namely, whether or not it is a single formation. Vanuxem care- 

 fully distinguished the upper portion of the formation, the so-called 

 "fucoidal layers," from the remainder, and he has been followed in this 

 by most other observers in the district.^^ In the main the few fossils 

 found in the formation have come from these fucoidal layers. According 



" Bulletin no. 95, New York State Museum, pp. 389-.390. 



*> While Ulrich's present views are of the greatest interest, they are based on the 

 study of a mass of unpublished material, which renders it impossible to discuss them 

 here. It is greatly to be hoped that his results may be published in the near future. 

 =1 Vanuxem : Geology of the Third District, pp. 30-37. 

 Darton : 13th Annual Report State Geology, pp. 417-422. 

 Cumlngs : Bulletin no. 34, New York State Museum, pp. 434-435, 441-442. 



