THE GEOLOGICAL HISTORY OF NEW YORK STATE 75 
At the close of the Paleozoic, and as a result of the Appalachian 
uplift, the region of New York State was raised well above sea 
level, with the greatest uplift toward the north as shown by the 
general south to southwesterly dip (tilt) of the Paleozoic strata 
(see figures 3 and 5). At that time those strata lapped over much 
of what is now the Precambric rock area of the Adirondacks. The 
Appalachian folds of the Hudson valley region, as well as the high- 
lands (of earlier origin) in general along the eastern border of 
the State, must have prevented any important eastward drainage. 
Thus, in the writer’s belief, the strongest evidence suggests that the 
principal streams of the early Mesozoic era flowed in general 
southwesterly courses upon the surface of the newly upraised 
Paleozoic strata and away from the highlands of the eastern border 
of the State.t 
If this be the correct interpretation (for others are certainly pos- 
sible) of the early Mesozoic drainage, it must follow that no river 
at all comparable in length and position to the present Hudson 
could have existed along the eastern side of the State, and no large 
rivers, like the Susquehanna and Delaware, then had southeasterly 
courses across the Appalachian mountains. 
During the long Mesozoic era, the area of the State was pro- 
foundly eroded, as already proved. In the midst of this era the 
ruggedness of Mesozoic relief reached its maximum and, in accord- 
ance with well-known principles, the valleys must have formed 
along the belts of softer rock, while the harder rocks stood out to 
form the highlands or ridges. At this time the edges of the Paleo- 
zoic strata had sufficiently retreated (by erosion) on all sides from 
the central Adirondacks so that a considerable area of Precambric 
rocks had already become exposed in northern New York. During 
this retreat of the Paleozoic strata there was a tendency to form 
important valleys, especially along the western and southern bor- 
ders of the Adirondacks, because whenever the harder rock forma- 
tions were encountered they would stand out as escarpments, while 
the softer rocks would be worn down into valleys. It is in accord- 
ance with these principles that the Mohawk and Black river valleys 
were formed, though it does not necessarily follow that these older 
valleys occupied the same positions as the present ones because of 
the gradual retreat of these depressions away from the Adirondack 
region. 
1Tt should be stated that the Great Lakes were not then in existence, those 
bodies of water not having been formed till late in the Cenozoic era (see 
chapter 6). 
