88 NEW YORK STATE MUSEUM 



the Pamelia (Chazy) limestone was being deposited in the Black 

 river valley and also locally along the eastern border when cer- 

 tain other limestones of the Chazy group were being laid down 

 in the Champlain trough. 



For most part the various Black River limestone members are 

 thin and patchy in their distribution except in tfie Black river 

 valley, and no attempt is here made to enter into the details of 

 physiography and oscillations of level in Black River time. Suf- 

 fice it to say that early Black River (Lowville) limestone is pres- 

 ent on all sides of the southern Adirondacks and in the outlier 

 at Wells, it being but a few feet thick in the eastern and southern 

 portions and fifty to sixty feet thick along the western border. 

 Therefore, judging by the areal distribution and thinness of the 

 Lowville we are practically certain that the central western por- 

 tion of the Adirondack area was not submerged during early 

 Black River time. Thin limestone deposits of late Black River 

 age are confined to the vicinity of Watertown (Watertown 

 limestone) and along the eastern and southeastern borders of the 

 Adirondacks (Amsterdam limestone) with deposition in these 

 two regions not occurring simultaneously. Thus there could not 

 have been anything like extensive submergence of the southern 

 Adirondacks in late Black River time. 



The widespread unconformity at the summit of the Black River 

 group of limestones shows that a general upward oscillation occurred 

 and that the whole southern Adirondack region became dry land 

 before the succeeding Trenton submergence. 



Late Ordovicic. During Trenton time there was a widespread 

 submergence of much of the southern Adirondack region as shown 

 by the existence of Trenton limestone or shale hundreds of feet 

 thick on all sides of the region and even in the outlier at Wells. The 

 limestone is almost wholly confined to the western side, there being 

 but a few feet of limestone at the base of the Trenton on the 

 eastern side where thick shales (Canajoharie and Schenectady) 

 comprise nearly the whole section. 



Considering the thickness (about four hundred feet) of the 

 Trenton limestone in the upper Black River valley and the slope of 

 the surface^ on which deposition occurred, the Trenton sea could not 

 have extended more than forty miles eastward into the Adirondack 

 area. If we consider deposition to have taken place in a distinctly 

 downwarped trough, then the Trenton sea must have extended in 



9 Page 43. 



