Handbook of Paleontology 315 



New York formations. At the close of the Ordo- 

 vician New York State was practically dry land and 

 undergoing erosion. The only very high lands were 

 found in the Taconic range along the eastern side and 

 the central Adirondacks. Silurian rocks are found out- 

 cropping in a narrow belt along the west side of the Hud- 

 son valley extending to the Helderberg mountains south- 

 west of Albany (figures 34, 42, 43). Here the beds 

 turn abruptly westward, following the south side of the 

 Mohawk valley, and south of Lake Ontario the belt be- 

 comes much wider. Silurian rocks underlie the younger 

 rocks (figure 44) throughout the rest of the State, 

 which indicates that through much of Silurian time the 

 present area of New York south of Lake Ontario and 

 the Mohawk valley and west of the Hudson river was 

 submerged. As shown by the tables of formations the 

 central and western parts of the State were submerged 

 first. The first formation deposited in central New York 

 was the Oneida conglomerate of lower Clinton age (base 

 of Middle Silurian) ; in southeastern New York, the 

 Shawangunk grit or conglomerate which is now consid- 

 ered to be as young as Clinton and has been placed in 

 the Medinan (Lower Silurian). It was not until late in 

 the period that the sea encroached upon the Hudson val- 

 ley to the western slopes of the Taconic mountains. There 

 is no evidence that the northern Adirondack area was 

 submerged during Silurian times. It was probably ele- 

 vated at the time of the Taconic Disturbance (close of 

 Ordovician) and has remained dry land ever since except 

 for local submergence during the Pleistocene (Qua- 

 ternary). Both Silurian and Devonian strata un- 

 doubtedly lapped upon the southern Adirondack area, but 



