GEOLOGY OF THE LUZERNE QUADRANGLE 59 



siderable depths. We also know that this work of erosion pro- 

 gressed far enough to reduce the whole Adirondack region to the 

 condition of a more or less perfect peneplain. The character of 

 this old peneplain surface upon which the Paleozoic rocks rest has 

 been carefully studied on all sides of the Adirondacks, and it is 

 known to be moderately rough in the northeast and very smooth 

 in the southwest. Within the Luzerne quadrangle the old peneplain 

 surface has of course been modified beyond recognition by sub- 

 sequent elevation, faulting and erosion, but from what we know 

 about it within the Little Falls, Broadalbin and Saratoga quad- 

 rangles, we can be sure that, during the late Cambrian period, there 

 could have been no more than occasional knobs perhaps 50 to 75 

 feet high projecting above the general surface. 



The vast peneplain gradually became submerged under an en- 

 croaching sea in which the Potsdam, Theresa and Little Falls 

 formations were successively deposited. As shown by the marine 

 character and present distribution of these formations, the waters 

 must have spread over the whole southeastern Adirondack region 

 including the area of the Luzerne quadrangle. 



Within the quadrangle, positive data regarding the Ordovician 

 history are lacking. It is known, however, that all of northern New 

 York was moderately above sea level toward the close of the Cam- 

 brian, and that submergence again occurred during the Ordovician 

 so that, toward the middle of that period, all but probably a large 

 low island in the east-central Adirondack region was under sea 

 water. It is highly probable that, during part of the Ordovician 

 period at least, the sea spread over the whole area of the quad- 

 rangle and that the deposits of that age have been completely 

 removed by erosion. 



There is no reason to believe that marine waters ever spread 

 over more than the fringe of the Adirondack area at any time since 

 the Ordovician. In other words, the Adirondack district has been 

 a land area undergoing erosion ever since Ordovician time. 



Mesozoic and Cenozoic History 



As a result of the long process of erosion from the Ordovician 

 to late Mesozoic or very early Cenozoic time, most of northern 

 New York was reduced to the condition of a fairly good peneplain 

 with some masses of relatively resistant or favorably situated rocks, 

 especially in the east-central Adirondacks, rising to moderate 

 heights above the general level of the country. 



