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NEW YORK STATE MUSEUM 



have a considerable pitch, and the writer's impression is that in 

 the northern part of the region at least, the pitch is to the north. 

 The major folds would seem to be broad and not excessively 

 steep, but their limbs are corrugated by minor folds also, and it 

 is in these that the steepest dips are obtained. 



The great igneous batholites of the Adirondacks are massed 

 in the east center of the region. Going west and south, a zone 

 is passed through marked by increase in Grenville sediments 

 and diminution of igneous rocks. On the west and south the 

 sediments largely predominate. It is in these areas that the 

 folds must be worked out, -provided they can be worked out at 

 all. If so, the knowledge thus obtained may be, perhaps, suc- 

 cessfully applied to the elucidation of the structure of the more 

 difficult interior area, more difficult because of the much larger 

 content of poorly foliated igneous rocks. The writer's work 

 has been mainly in the latter district. It ought to be possible 

 with good maps and careful areal work, to make out the axes of 

 at least the larger folds. The folding was certainly done in 

 Precambric times and while the rocks were buried at some 

 considerable depth; hence it long preceded the period of diabase 

 eruption, and these dikes are wholly unaffected by it. 



Folds 



Aside from the folding of the Precambric rocks, just noted, 

 which was produced in Precambric times, the rocks of the 

 region are but slightly folded. Along Lake Champlain the 

 Paleozoic rocks are thrown into a series of very gentle folds, 

 which have subsequently been so much faulted that the folding 

 is not always apparent. Across the lake in Vermont the folds 

 become rapidly more pronounced, but on the Xew York side 

 only a trifling amount of folding has taken place. The dips 

 are in general very low. and in many cases so flat that they are 

 made out only with great difficulty. They are almost always 

 below 10° and usually below 5°. In the few instances where 

 they are steeper, the cause is usually found to be the tilting of 

 a small fault block, or drag in the vicinity of a fault. A steep 

 dip may usually be taken as an indication of proximity to a 

 fault. However, the rocks are unquestionably slightly folded, 

 marking in all probability merely the waning effects of the force 



