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NEW YORK STATE MUSEUM 



Forestport, Remsen, Bardwell Mill, one on Little Black creek, 

 Northwood, Grant, and a large pulp mill at Hinckley, within the 

 territory. The southwestern half of the region is devoted pri- 

 marily to agriculture and dairying. 



GENERAL GEOLOGIC FEATURES 



Under this heading it is proposed to briefly outline the geologic 

 history of the whole Adirondack region so that the detailed study 

 presented in this report may be made more intelligible to the reader. 

 This outline is largely based on the admirable treatises of Prof. H. 

 P. Cushing. 



So far as known the oldest rocks of the Adirondacks are those of 

 Grenville (Precambric) age. They are sedimentary rocks, origin- 

 ally shales, sandstones and limestones, which have been highly 

 metamorphosed into gneisses and crystalline limestone. These 

 rocks are of unknown though great thickness, and are widely 

 scattered throughout the Adirondacks, thus showing that the 

 whole region was under water at the time of their deposition. 

 * After the deposition of the Grenville sediments the region was 

 raised above the ocean level and the rocks began to decompose 

 and suffer erosion. Either just before, during or after the uplift, 

 great masses of igneous rocks were intruded. The Grenville rocks 

 were for the most part engulfed by the intrusion so that only 

 occasional patches of them were left intact. 



After the igneous activity the rocks became thoroughly meta- 

 morphosed by being squeezed, highly folded and converted into 

 gneisses. Such changes can take place only at great depths (several 

 thousand feet) and hence we are led to the belief that a vast erosion 

 of the original land masses must have taken place. This in turn 

 signifies that the land masses must have remained above sea level 

 for an immense length of time. 



At or toward the close of this long period of erosion, igneous 

 activity of a minor character took place. The basic igneous 

 rocks erupted at this time are especially well shown in the north- 

 eastern Adirondacks where they were squeezed up between joint 

 planes in the older rocks. That these rocks are much younger 

 than the igneous rocks first mentioned is clearly shown by their 

 mode of occurrence and their general lack of metamorphism. 



At the conclusion of the erosion period the region of the Adiron- 

 dacks was nearer the sea level and of slighter i^lief than at present. 

 Then the whole region began to sink slowly, allowing the sea to 

 encroach upon the land until only an island was left or probably 



