102 NEW YORK STATE MUSEUM 



Brainerd and Seely, 1890. 1 In a most important paper Brain- 

 erd and Seeley give results of the first careful and detailed study 

 made of the Calciferous of the Champlain valley, disclosing its 

 great thickness and its considerable fauna. They distinguish 

 five subdivisions of the formation which they call divisions A-E, 

 inclusive, and map several of the most important areas in detail. 

 The work on the whole was well done and has formed the basis 

 for all subsequent discussion of these rocks in the Champlain 

 valley. 



Prosser and Cumings, 1896-1900. 2 In two publications are 

 given a series of carefully measured sections with discussion, 

 from Trenton Falls on the west through the Mohawk valley to 

 the Saratoga region on the east. The thickness of the Little 

 Falls dolomite in the Mohawk valley was made known for the 

 first time and, following Vanuxem, the fucoidal layers were care- 

 fully distinguished from the dolomite beneath. 



Cleland, 1900-3. 3 Announces discovery of an abundant fauna 

 in the Mohawk valley Calciferous (fucoidal layers) which is de- 

 scribed, and the horizon traced from Fort Hunter and Tribes Hill 

 to Little Falls with collection of fossils at several points. 



Cushing, igo8. 4 Gives a general description of the section in 

 Jefferson county, describing the Theresa formation — a thin 

 series of passage beds and following magnesian limestones — 

 which directly overlies the Potsdam sandstone and is uncon- 

 formably overlain by the Pamelia formation, of late Stones 

 River age. The Theresa formation was so thin and so litholog- 

 ically similar from base to summit, that it was not suspected 

 that more than one formation was represented by it. This, how- 

 ever, proves to be the case, as will be later shown. 



It is also argued in this paper that division A of the Beekmantown 

 more properly belongs with the underlying passage beds and Pots- 

 dam than with the purer limestones of the remainder of the Beek- 

 mantown, and that with this readjustment the upper Cambric 

 (Ozarkic) and the Lower Ordovicic are separated by an uncon- 

 formity everywhere in northern New York. 



Purpose of this paper 



Our comparative study of the region has, we think, made clear 

 the correlation of the Calciferous of the Champlain and Mohawk 



'Am Mus. Nat. Hist. Bui. 3:1. 

 2 N. Y. State Geol. 15th An. Rep't, p.619-59. 

 N. Y. State Mus. Bui. 34. 



3 Am. Pal. Bui. 13, 18. 



4 Geol. Soc. Am. Bui. 19:155-76. 



