142 1L P. Gushing — Lower Paleozoic Rocks of New York. 



culties arose in the Chainplain sections, and Ulrich urged 

 difficulties without the State, which rendered it impossible to 

 give either of the names Lowville and Black River as wide 

 application as they might otherwise secure. If we adopted 

 Hall's restricted use of Black River we practically wiped it 

 out as a New York name, since the 7 foot tier is thin and 

 occurs only about Watertown. It was finally decided, there- 

 fore, that it would be best to revert to Vanuxem's usage 

 (except for the inclusion of the Chazy) and to apply the name 

 Black River to the entire rock group between the Trenton 

 and the Chazy, the usage which the Geological Survey of 

 Canada has consistently followed. The Lowville thus becomes 

 the lower division of the Black River group. The black, cherty 

 beds of the Watertown region, between which and the typical 

 Lowville an unconformity exists, we class provisionally as the 

 uppermost member of the Lowville, and name it the Leray 

 formation, from the river exposures in Leray township, Jeffer- 

 son county. The section there is, however, not complete. At 

 Lowville, for example, is a thickness of 5'6" of cherty lime- 

 stone with Columnaria halli and Stromatocerium rugosum 

 not seen at Watertown. And to the south, at Newport, in the 

 valley of West Canada creek, this Stromatocerium bed is the 

 sole representative of the formation, the remainder having 

 disappeared. 



The Champlain valley seems a wholly separate trough of 

 deposit for these beds. There is present a trifling thickness 

 only of Lowville proper, followed by black, massive beds in 

 much greater thickness than elsewhere in New York. The 

 upper portion of these black beds seems to represent the Leray 

 horizon, and the remainder to bridge the interval represented 

 by the break between the Lowville and Leray in the Water- 

 town sections. The Champlain succession seems unbroken, 

 but deposit did not commence there till late in Lowville time. 



The upper subdivision of the Black river group in New 

 York (the Lowville being the lower) is nowhere represented 

 by any considerable thickness of deposit, with the possible 

 exception of the extreme east, where the shales of the Levis 

 channel, overthrust to the west, are met with. Otherwise the 

 deposits are thin, scattered, and of quite varying age, indicat- 

 ing repeated oscillations and prevalence of near shore condi- 

 tions throughout. In the Watertown sections we group with 

 the 7 foot tier the massive bed below, and the thin one above, 

 into a formation of 13' thickness which we call the Watertown 

 limestone. It occurs only in the immediate vicinity; and other- 

 wise there is no representative of the upper Black River on 

 the western side of the Adirondack region. 



