502 W. H. HOBBS — LINEAMENTS OF ATLANTIC BORDER REGION 



Along the joint planes of the district faults were in many cases ob- 

 served, the present structure being ascribed to folding and in part to 

 faulting. The maps included with the paper show that the present 

 formation boundaries have been largely determined by planes of fault- 

 ing, and that the rock masses form a mosaic, which the author compares 

 with the one described by Davis from the Connecticut valley * In the 

 areas lying within the uplands of southwestern New England, which 

 the present writer has studied in detail, a correspondence of fault and 

 joint directions has been established, and it is found that for both alike 

 the dominant directions are near the meridian (north ± 5 degrees west); 

 near the equatorial direction (north 85-90 degrees west), and in direc- 

 tions in part nearly bisecting them (north 50-55 degrees east and north 

 15 degrees east and north ± 34 degrees west and north ± 44 degrees 

 west). 



Cushing has described the joints and faults of Rand hill, in northern 

 New York state.f He describes the master joints as trending princi- 

 pally along the meridian, or parallel to the equator. Other sets cut 

 these directions at about 45 degrees. He adds, however, that many 

 joints have been noticed which can not be brought into any of these sets, 

 but that these are of much less importance. Of the faults he says : 



" The faults run in all kinds of directions. The greatest breaks have a general 

 north and south trend, though they may depart from this as much as 45 de- 

 grees. Instead of being persistent in direction, they curve largely. The down- 

 throw is always on the east side, with the result that progressively younger blocks 

 appear as lake Champlain is approached. The general rude parallelism of these 

 faults cuts up the region into a series of land slices. These are cross- faulted some- 

 times repeatedly as in the case of the block on the east of the Tracy Brook fault, 

 but usually much less frequently. The cross-faults have a general east and west 

 trend, but depart widely from that, and may or may not be normal to the main 

 faults." . . . 



" The majority of the faults of the region are certainly normal (gravity) faults, 

 and this is likely the case with all " (p. 73). 



In the Adirondack region both Cushing and Kemp ascribe the valleys 

 largely to faulting. J Professor Kemp says : 



"There is much reason to regard these valleys as chiefly due to faults and the 

 mountain ridges as of the block tilted type, but in massive and metamorphic rocks 

 this can not be as readily shown as in continuous and contrasted sediments. . . . 

 The evidence leading one to ascribe many of the valleys to faults can be briefly 

 summarized as follows : 



*Loc. cit., p. 502. 



t H. P. Cushing : Geology of Rand hill and vicinity, Clinton county. Nineteenth Annual Re- 

 port State Geologist, New York State Museum, 1901, pp. 39-82, map. 



t J. F. Kemp : Preliminary report on the geology of Essex county. Rept. New York State Geol, 

 Survey, 1893, Albany, 1894, pp. 438-440, 



