FOURTH REPORT OF THE DIRECTOR i.907 II 



Northern New York. Since my last report the Long Lake 

 map and accompanying report by Prof. H. P. Gushing have been 

 issued. 



Professor Cushing's work in the past season has continued upon 

 the Theresa and Alexandria quadrangles which also involve prob- 

 lems pertaining to both the crystalline and the sedimentary rocks. 

 The mapping of the former was completed last season. In the 

 work on the Paleozoic sediments which required the aid of a paleon- 

 tologist, Dr Ruedemann assisted with the cooperation by invitation 

 of Mr E. O. Ulrich of the United States Geological Survey. Mr 

 Ulrich's intimate acquaintance with rocks of similar age in other 

 parts of the country rendered his collaboration of much value. 



During the previous season the Potsdam sandstone had been 

 studied and was found everywhere to grade upward into a dolo- 

 mite formation quite like the rocks which elsewhere immediately 

 overlie the Potsdam around the Adirondacks and which have been 

 regarded and mapped as passage beds into the Beekmantown for- 

 mation above. It was naturally expected that the Beekmantown 

 formation w^ould be present here, to be followed in proper succession 

 by the Lowville, Black River and Trenton limestones. In working 

 downward from the Trenton as the summit rock of the quadrangle, 

 the Black River limestone appeared with a thickness of some 20 

 feet and with a sharp lithologic boundary separating it from the 

 Lowville beneath. 



The upper part of the Lowville proves to be abundantly fossil- 

 iferous, but when followed downward these fossiliferous limestones 

 are succeeded by others which carry an abundant ostracode fauna 

 but with little else. These two limestones have a combined thick- 

 ness of some 75 feet. Just beneath them follows a considerable 

 thickness of Avhitish,. very impure limestones, sometimes shaly, 

 alternatmg with occasional beds of pure limestone and of dolomitic 

 limestone with again an ostracode fauna. This mass has a thickness 

 of about 80 feet and beneath it lies a 10 foot mass of pure blackish 

 limestone with many fossils, mainly gastropods but with some 

 cephalopods and trilobites. There is some mixture of Lowville 

 form? in this fauna but in the main it consists of forms which 

 do not pass up into that formation. The fauna appears to be one not 

 before noted in New York, and according to Mr Ulrich seems com- 

 parable with the fauna of the upper Stones River formation of other 

 regions. Its close association with the Lowville, both stratigraphi- 

 cally and paleontologically, seems to preclude its reference to the 

 Beekmantown formation and its fauna is whollv different. The 



