50 NEW YORK STATE MUSEUM 



portion of the southern Adirondacks, though proofs are wholly 

 lacking. There is no reason whatever to think that any of northern 

 New York was, submerged during the last two periods of the 

 Paleozoic era. 



The Paleozoic era was brought to a close by one of the most 

 profound physical disturbances in the history of North America. 

 It has been called the Appalachian revolution because at this time 

 the Appalachian mountain range was borne out of the sea by fold- 

 ing and upheaval of the strata. The effect of this revolution upon 

 northern New York is of fundamental importance because the 

 whole region was then raised well above sea level, though without 

 folding of the strata but with moderate tilting toward the south, 

 and true marine conditions never again prevailed over any part of 

 the area. 



Mesozoic History 



The vast plain. of erosion. During all the Mesozoic era most of 

 the eastern portion of the United States was above water and 

 undergoing erosion, so that, by the close of this very long period 

 of wear, the region was reduced to the condition of a more or less 

 monotonous plain near sea level (peneplain). This vast plain 

 extended over the areas of the Appalachian mountains, Piedmont 

 plateau. New York State, the Berkshire hills and the Green moun- 

 tains. Its most perfect development was in the northern Appa- 

 lachians. Farther northward, over New York and western New 

 England, its development was less perfect so that certain masses of 

 harder rock stood out more or less prominently above the general 

 level of the plain. In the central and eastern Adirondacks many 

 low mountains of resistant rock rose above the peneplain surface. 

 Hence this second definitely known peneplain of northern New 

 York was not so perfectly developed as that of very early Paleozoic 

 time already described. In a similar manner an occasional low 

 mountain stood out in western New England, and it is probable 

 that the hard sandstone3 of the Catskills also rose notably above the 

 peneplain. 



In the eastern United States the Mesozoic era was closed, or the 

 Cenozoic era opened, by an important physical disturbance which 

 produced an upwarp of the peneplain for from two to three thous- 

 and feet following the trend of the Appalachians thence through 

 northern New York. This upward movement Avas unaccompanied 

 by folding of the rocks, the efifect having been to produce a very 

 broad, low arch sloping gently eastward and westward. We are 

 now prepared to make the important statement that the major 



