REPORT OF THE DIRECTOR I914 39 



of lowermost Beekmantown age. On the Brier Hill sheet the 

 Theresa beds thicken and become more sandy, and are followed 

 above by a sandstone, 20 feet thick, and sandy dolomites which 

 carry a large fossil gastropod sparingly. This is, according to 

 Ulrich, a quite distinct formation from the underlying Theresa, and 

 considerably younger, the gastropod indicating an age either very 

 late in the Ozarkic, or very early in the succeeding Beekmantown. 

 The specimens so far found do not suffice for precise identification ; 

 but no fossils of the type are known anywhere in rocks as old as 

 the normal Theresa. The zone is, so far as known, a new one in 

 the New York section. 



The Tribes Hill formation occurs but sparingly in the district. 

 But a few thin patches of it have been noted on the Brier Hill sheet. 

 Across the Ogdensburg sheet it thickens, but the heavy drift cover 

 there hides all the formation with the exception of two or three 

 scattered outcrops which give no idea of its thickness or importance. 



Unconformably overlying these formations, with a very varying 

 thickness of the Tribes Hill underneath, comes a much higher 

 Beekmantown formation which we are proposing to call the Ogdens- 

 burg formation, the new name being necessary because both it and 

 the Tribes Hill are of Beekmantown age, and yet are separated by 

 a considerable unconformity. Nearly the entire formation is 

 well shown in the river sections within 2 miles of Ogdensburg. 

 From here the formation runs continuously down the river below 

 Ogdensburg, but the country is so heavily drift covered that out- 

 crops are few and thin and give but little knowledge of the for- 

 mation. Hence dependence for our knowledge of the formation 

 will have to be chiefly upon these excellent exposures just west of 

 Ogdensburg. Not only are the exposures excellent but the for- 

 mation is unusually fossiliferous for a Beekmantown formation, 

 and the fossils are unusually well preserved. 



The formation consists of thick beds of granular, blue-gray dolo- 

 mite, alternating with thinner bedded, fine-grained, iron-gray layers. 

 Four or five distinct fossil zones have been recognized ; Ulrich has 

 determined the species and correlates the formation with division D 

 of the Beekmantown of the Champlain section. He states that " the 

 fauna of division E is not even suggested, while none of the species 

 are of those which are particularly characteristic of the fossil beds 

 at Fort Cassin." 



The Survey has had the services of Professor Chadwick on the 

 Canton quadrangle, next east of the Ogdensburg area, in completion 

 of the work on the crystalline rocks which, during the previous 



