58 NEW YORK STATE MUSEUM 



enough for marine invasion. From time to time it may have 

 received a coating of continental deposits, in fact the Oswego sand- 

 stone may have been deposited here in considerable thickness; but 

 all trace of these is now gone. We are, however, obliged to assume 

 the original presence here of formations younger than the Beekman- 

 town for the reason that some considerable thickness of rock has 

 certainly been eroded away from the region in the vast lapse of 

 time since the Ordovician. The most probable of such formations 

 are those whose present-day outcrops lie nearest the region, such 

 as the Pamelia, Chazy, Black River and Trenton, Lorraine and 

 Oswego. 



During all of Paleozoic time the Adirondack region seems to have 

 persisted as a continuous land area, submerged frequently on one 

 or more sides ; seldom or perhaps never on all four sides at once, 

 and the interior probably never submerged at all. 



No doubt the district participated in the considerable uplift of the 

 eastern part of the continent at the close of the Paleozoic, the 

 so-called Appalachian revolution, when it may for a time have had 

 an altitude of many hundreds of feet above sea level. But the St 

 Lawrence valley has always had a tendency to sag, as compared 

 with the territory to the north and south. How^ much this inherent 

 tendency may have counteracted that uplift, it is impossible to say. 



MESOZOIC HISTORY 



In common with all the eastern portion of North America, with 

 the exception of a narrow, marginal strip along the Atlantic and 

 Gulf coasts, the Ogdensburg region was a land area and undergoing 

 wear. In this long interval the erosion was so great that the 

 entire area was apparently worn dow^n to a comparative plain, or 

 peneplain. No trace of this peneplain remains in the Ogdensburg 

 region, as subsequent wear has entirely obliterated it; but there is 

 strong probability that it was produced here. 



TERTIARY HISTORY 



Uphft of the region followed after its peneplanation, and erosion 

 began the development of another peneplain. During the Tertiary 

 there w^as more than one such oscillation, during which the district 

 imderwent partial peneplanation, A great peneplain level is today 

 discernible in the even levels of the hilltops of the western Adiron- 

 dacks, of the Oswego sandstone plateau, and of the plateau region 

 of southern New York. This may represent the Cretaceous pene- 



