56 NKW Y(,)RK STATE Ml'SEl'M 



llumi^h faulting has no doubt been a notable factor in the produc- 

 tion of the Champlain valley. The numerous lakes, gorges and 

 waterfalls of the Adirondacks have all come into existence during 

 Cenozoic time, most of them since relatively late Cenozoic time. 



During the Cenozoic era, still more of the Paleozoic strata which 

 rested upon the Prepaleozoic rocks and extended over the present' 

 borders of the Adirondacks were stripped otT by erosion until the 

 present condition has been reached. Thi.; removal of Paleozoic 

 strata around the Adirondacks is still going on, thus gradually 

 enlarging the area of the very ancient Prepaleozoic rocks. The 

 little masses of Paleozoic strata well within the Adirondack borders 

 such as those at Wells, Schroon Lake, North River, etc.. are merely 

 erosion remnants of the mantle of Paleozoic sediments which 

 formerly spread over all the southeastern .Vdirondack area. 



Of much greater intiuence than the faulting in the production of 

 the present-day Adirondack relief features has been the diiTerence 

 in character of the rock masses. Thu.^ the relatively weaker Gren- 

 ville strata (especially limestone) have almost invariably been worn 

 down to form the valleys, while the harder and more resistant 

 anorthosite, granite and syenite have stood out better against the 

 weathering and erosion to form the luountains. It will be recalled 

 that the Grenville strata and the igneous rocks are very irregular or 

 *' patcbv " in their distribution. For this reason the valleys and 

 luountains have been carved out in a most irregular manner through- 

 out the Adirondack region except where the faulting has had a 

 notable intiuence. In man\- instances in the faulted region, streams 

 have cut relatively straight channels for greater or lesser distances 

 along the broken-rock fault zones. But by no means all the relief 

 has developed either as a re.'ult of ditlerences of rock character or 

 faulting, because even in large masses of very homogeneous hard 

 rocks many streams have developed channels of varying size and 

 shape in a most irregular manner. 



The evolution of drainage. Almost nothing is definitely known 

 about the positions of drainage lines in northern New York before 

 the Cenozoic era began. Since the uplift of the peneplain in the 

 late ]Mesozoic or early Cenozoic, however, the drainage history of 

 the Adirondacks is fairly known. As already pointed out, the 

 present Adirondack streams show a very marked tendency to 

 radiate from the central portion of the district. The Adirondack 

 region is now a broad, relatively low, domelike mass fully a hundred 

 miles across with altitudes cotnmonlv ranging from 1000 to several 

 thousand feet, the central to east-central portion being the highest. 



