ALG ONKIA N RO CKS IN VERMONT. 4 2 1 



age is produced. A beautiful example of this is seen in 

 Fig. I, from the schist phase of the conglomerate gneiss two 

 miles north-east of East Clarendon, near its contact with a coarse 

 underlying gneiss. Blue Ridge and Pico Mountains are now 

 capped by schist produced upon the back of folds. Close fold- 

 ing with axes striking nearly north and south only occurs in the 

 amphitheatre near the summit of the greatest elevations, as on 

 Mount Holly — a hill about a mile south of the station by that 

 name — and near the contact with the Mendon series. The rocks 

 of the core have no presistent strike and dip, neither of schistosity 

 nor bedding ; east and west strikes are as numerous as those trend- 

 ing north and south and the dips are as variable. Throughout the 

 core the gnarled and tortuous folding of the strata represents the 

 effect produced by the operation of repeated periods of mountain- 

 building action of enormous force, directed not always from the 

 east and west as in the Mendon series, but from the north and 

 south as well. 



A careful study of the Mendon series recognizes but two 

 periods of orographic disturbance, the second acting along 

 approximately the same lines as the first. This is well-indicated 

 under the microscope, and in the field it is beautifully shown at 

 North Sherburne where the strike of the rock (a conglomerate) 

 is N. 25° W.- — a trend produced by the first period of folding. 

 The schistosity of the Green Mountains traverses this obliquely, 

 making an angle of 35°-40°, striking N. 10° to 15° E. Both 

 structures dip easterly at a variable angle. Forces that induced 

 the regional lamination of the range could not have produced 

 the great variety of trend observed in the folding of the Mount 

 Holly series. The question of difference of environment of the 

 central or lower parts of anticlines as compared with the outer 

 must not be overlooked. All the phenomena go to show that 

 the superior or Mendon series was above the neutral zone and 

 that great slipping, stretching and crumpling took place therein 

 dependent upon position in this belt. Below the neutral zone 

 during the folding of the Mendon series undoubtedly most of 

 the core rocks were placed where crushing would largely 



