﻿g6 NEW YORK STATE MUSEUM 



began in the Champlain region, and what has there been called 

 Black River limestone commenced its accumulation. This deposit 

 consists of a small thickness of typical Lowville at the base, the 

 equivalent of the Leray limestone at the summit, and interme- 

 diate beds which represent the Lowville-Leray hiatus of the north- 

 west; while the Watertown limestone is lacking. With our sug- 

 gested nomenclature this may still be properly called Black River, 

 while on any other arrangement it could not be so called. The 

 Mohawk region was close to the shore line throughout Black River 

 time and received only the very thin, near-shore edge of the deposits 

 of the group, never more than a few feet thick, often practically 

 absent and varying much in horizon from place to place. 



At the close of the Leray, uplift was widespread and the Water- 

 town limestone is practically absent except in that locality, in strong 

 contrast with the widespread occurrence of the preceding Leray. 

 Then followed subsidence on the east with accumulation of the 

 Amsterdam limestone, which is wholly absent on the west. Then 

 ensued on all sides of the region the Trenton submergence; lime- 

 stone quickly followed by black shale on the east so that the bulk 

 of the eastern Trenton is of shale; the shale gradually encroaching 

 westward, but the western Trenton, of the type locality and north- 

 ward, remaining of limestone throughout. The black shale of the 

 Utica followed, with northern New York more largely submerged 

 than at any other period in its geologic history, the Grenville pos- 

 sibly excepted. Possibly the Adirondack island was entirely sub- 

 merged. With the close of the Utica local elevations began to ap- 

 pear, and by the close of the Ordovicic much of the State was again 

 unsubmerged. Since then most of northern New York has re- 

 mained a land area. The appended chart will, it is hoped, aid in 

 the understanding of these views. 



