REPORT OF THE DIRECTOR AND STATE GEOLOGIST 



r73 



dike unmistakable, and frequently enough to emphasize the great 

 number of these small slips that must exist. The slickensided 

 character of many of the joint planes is evidence of slipping along 

 them. 



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 3 . Instead of being persistent in direc- 

 tion, they curve largely. The downthrow is always on the east 

 side, with the result that progressively younger rocks appear as 

 Lake Champlain is approached. The general rude parallelism of 

 these faults cuts up the region into a series of long slices. These 

 are cross-faulted, sometimes repeatedly as in the case of the block 

 on the east of the Tracy brook fault, but usually much less fre- 

 quently. 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. No case has been met with where one crosses a 

 main fault. They are necessarily of less magnitude though often 

 with throws of many hundred feet. 



The majority of the faults of the region are certainly normal 

 (gravity) faults, and this is likely the case with all. The rocks 

 lie in exceedingly gentle folds, and thrust faults, if present, must 

 hade to the west, as all the great faults downthrow to the east. 

 Across the lake the rocks are more sharply folded, and there 

 thrust faults occur, but with a hade to the east. 



Joints. All the rocks of the region are cut by joints and gener- 

 ally by several sets. Unfortunately observations on them do not 

 suffice definitely to determine their character; observations on 

 the strike are plentiful, but the dips can seldom be made out. 



The most common direction of joints is a nearly north and south 

 one varying between n 20° w and n. In nearly every case in 

 which these are observed joints at right angles can also be made 

 out, from n 70 c e to e. In the majority of exposures these seem 

 to represent the master joints. But northeast and northwest 

 joints are nearly as common and in many exposures seem more 

 prominent than the other set. There are evidently two sets of 

 main joints, each consisting of a pair at right angles to each other, 



