^O NEW YORK STATE MUSEUM 



(horst) of Precambric rock covering at least one hundred square 

 miles and including all of the high country in the northeastern por- 

 tion of the Broadalbin and the northwestern portion of the Sara- 

 toga quadrangles. It comprises the large tongue of Precambric 

 rock shown on the State geologic map between Saratoga Springs 

 and Northville. 



The profound influence of trough faulting upon the topography 

 in this region strongly suggests the occurrence of similar phe- 

 nomena well within the Adirondacks. As Professor Gushing 

 stated several years ago, the topography of the eastern Adirondacks 

 .often suggests faulting of this sort but positive proof has hereto- 

 fore failed. The finding of such a large and clear-cut trough fault 

 at the southern margin of the Precambric area greatly strengthens 

 the belief that faulting of this kind has had an important influence 

 upon the topography of the eastern Adirondacks. 



PHYSIOGRAPHY 



; PRECAMBRIC PHYSIOGRAPHY 



During Grenville times the physiography was very simple, the 

 whole Adirondack region being covered by ocean water and receiv- 

 ing an immense accumulation of sediments. Then came a time of 

 intrusion of tremendous igneous rock masses into the Grenville. 

 The whole region was uplifted some thousands of feet above sea 

 level. We have no knowledge of the character of the topography 

 of this land mass when it was high above the sea, but we know that 

 it underwent erosion for a vast length of time extending into the 

 early Paleozoic era. 



PALEOZOIC PHYSIOGRAPHY 



It is certain that, during the Lower and Middle Gambric, the Adi- 

 rondack region was above water and suffering erosion because Lower 

 and Middle Gambric strata are everywhere absent from the region 

 and, there is not the slightest evidence that they ever were present. 

 During the long Prepotsdam time the ancient Adirondack land mass 

 had become worn down to the condition of a peneplain or almost 

 smooth surface and the Potsdam (Upper Gambric) sea encroached 

 from the northeast upon this peneplain during its gradual sub- 

 sidence. By the work of Kemp, Smyth, Gushing, and the writer 

 it is now known that the surface of this peneplain was more or less 

 uneven, the greatest unevenness being along the northeastern border 

 of the Adirondacks and the smoothest surface along the southwest- 



