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NEW YORK STATE MUSEUM 



often show different inclinations. The close, compressed folds have 

 straight sides which dip in nearly the same direction. The arches 

 in such cases are often overturned so that one side rests upon the 



Fig. 3 Folded strata, showing a syncline bounded by two anticlines or 

 saddles 



other. Examples of the open types of folding are found in the 

 strata that lie on the borders of our mountain areas and are oc- 

 casionally seen in the limestones and sandstones of the Mohawk 

 and central Hudson valleys. In the interior of the mountains, the 

 folds become compressed or overturned and develop minor flexures, 

 superimposed on the larger ones so as to produce a very complicated 

 structure. 



Folding of the intense kind is accompanied by metamorphism. 

 The metamorphic rocks like marble, slate and schist are invariably 

 highly folded. So intricate is the result of this folding upon the 

 crystalline rocks of the Adirondacks, followed as it has been by 

 profound erosion, that the nature of the flexures are only rarely 

 determinable, though the high angles of dip and their conformity 

 for considerable distances indicate strongly compressed strata. 



The crystalline limestones and marbles, owing to their uniforrii- 

 ity and the readiness with which they yield to stress by plastic 

 movement, often effectually conceal the existence of folds. When 

 seams of slightly different character or stringers of foreign materials 

 are present, these will generally be found to be bent into a succession 

 of winds and inverted folds that exemplify in limited compass the 

 actual contortion that has taken place on a large scale. 



Fig. 4 Folding of the Paleozoic strata in the vicinity of Kingston, N. Y. 

 After N. H. Darton 



Great masses of igneous rock, like the areas of granite, syenite, 

 and anorthosite in the Adirondacks, undergo much less shortening 



