REPORT OF THE DIRECTOR I9IO 



igi 



FACTORS FAVORING THE FORMATION OF THE DOMES 



The very common occurrence of exfoliation domes, in the region 

 under discussion, requires explanation and the writer believes they 

 are due to a combination of factors pecuHar to this portion of the 

 southeastern Adirondacks. These factors may be discussed as 

 follows : 



I Character and distribution of the rocks. The kind of rock, 

 syenite or granitic syenite, forming most of the typical domes is 



Fig. 2 Geologic and topographic sketch map of the southwestern corner of the North Creek 

 (U. b- G. b.) sheet. Contour interval 100 feet. Conventions same as in figure i 



very favorable because of its medium-grained texture and homo- 

 geneity in large masses. The closely associated Grenville rocks, 

 on the other hand, are very variable in composition, generally dis- 

 tinctly banded, and especially rich in limestone, this last feature 

 rendering the Grenville unusually weak and liable to erosion. So 

 far as the mapping has progressed the syenite-granite series and 



