TRANSACTIONS. 



THE UTICA SLATE AND RELATED FORMATIONS OF 

 THE SAME GEOLOGICAL HORIZON. 



By C. D. Walcott. 



[Read before the Albany Institute, March 18, 1879.] 



The Utica Slate. 



Mohaiok slate, Black slate and shale, Frankfort slate, Oraptolitic slate, lorraine 



shales (in part) of the New York Geological Reports. 

 In part Professor Eaton's Transition argiUite, Wacke slate and Glazed .-i/att. 



No. 3 and the Matinal Black slate of the Pennsylvania Survey. 



The name Utica slate was adopted by the New York geologists 

 in their final reports for the black bituminous slates succeeding the 

 Trenton limestone in the Mohawk and Black River valleys — Prof. 

 E. Emmons retaining the term Lorraine shales for the upper 

 portion beneath the shaly sandstones of the Hudson River group, or 

 Lorraine sandstones as he termed them. The term Hudson River 

 group, with the Utica slate for a subdivision embracing the lower 

 slaty portion, was, however, generally received into geological no- 

 menclature. 



At the typical locality in the vicinity of L'tica the formation has 

 a thickness of over 600 feet, the upper part passing into the lighter 

 colored, more silicious slate, beneath the Oneida conglomerate; 

 this change of color and addition of silicious material, with the pre- 

 sence of a few thin sandy layers, alone representing the arenaceous 

 shales and sandstones of the Hudson River group in its extension 

 east and west from this p'oint. The Utica slate would otherwise be 

 a continuous formation from the Trenton limestone to the base of 

 the conglomerate. 



At Rome, fifteen miles west, the shaly sandstones increase in 



Trans, a?.] 1 



