14-t II P. Gushing — Lower Paleozoic Rocks of New York. 



limestone of lower Trenton age followed by shales and thin 

 limestone bands ; only in the western border sections (West 

 Canada creek and Black river) did limestone deposition con- 

 tinue through to the end of the Trenton. Much of shaly 

 Trenton has heretofore been called Utica. As the result of 

 recent work Ruedemann has the problem of the age of these 

 shales well in hand, and with most important results. 



Paleozoic Submergence of the Adirondack Region. 



Some years ago Cushing expressed the view that the entire 

 Adirondack region was submerged during Utica time, basing 

 the opinion on the thickness of the Champlain Paleozoic sec- 

 tion (Potsdam-Utica) and the present altitudes of the Precam- 

 brian summits of the Adirondacks. The assumption was that 

 the successive seas overlapped ever more extensively on the 

 oldland, without extensive downwarping of the marine troughs. 

 It was further thought that the Utica shale was found on all 

 sides of the region.* Shortly afterwards, and independently, 

 Ruedemann expressed the same view, his argument being that 

 the orientation of the graptolites in the shales indicates cur- 

 rents clear across the region. f 



Our recent results cast much doubt on the correctness of 

 these previous views. As the evidence accumulates it points 

 more and more strongly to deposit in downwarping troughs, in 

 which large depth of deposit by no means implies extensive 

 overlap on the shores. Usually also deposit on the east side 

 of the region was coincident with sea-withdrawal on the west, 

 and vice versa. Even when submerged at the same time, as in 

 the Trenton, the deposits on the two sides are so different, 

 both lithologically and faunally, as to indicate that the two 

 basins had no very direct connection. Entire submergence of 

 the Adirondack tract during the Utica appears unlikely. It 

 follows that there has been no complete submergence of the 

 area since the earliest Precambrian. 



Chart. — In order to present more concisely the nomenclature 

 modifications suggested in this paper, the chart below is here- 

 appended. It makes no pretence of completeness so far as the 

 major division are concerned, giving simply the chief groups 

 into which the rocks present are divided, their subdivisions, 

 and the general sections of the northwest, southwest, south, 

 southeast and northeast borders of the Adirondacks. 



* 18th Rep., N. Y. State Geol., pp. 76-7. 

 f Am. Geol., Feb. 1898, p. 75. 



