Invasion to Regional Metamorphism. 15 



first thick sheet, quartz infiltrations become noticeable, 

 then fine-grained garnets enveloped in muscovite. 

 Within a hundred feet the sediments become transformed 

 and at the contact are lustrous but fine-grained schists. 

 In between the granite sheets, the texture of the schists 

 becomes coarse and sparkling. Still farther northwest, 

 sheets of granite and pegmatite become more abundant, 

 the schist becomes feldspathized, crumpled, and of maxi- 

 mum coarseness, cyanite and garnet become abundant, 

 the proportion of magma increases, and the rocks pass 

 finally into truly igneous masses. In the region of Dan- 

 bury the granite gneisses envelop and intrude the 

 Stockbridge limestone, and it is found to be transformed 

 into a coarse white friable marble. 



The beginning of the intense anamorphism on this 

 section is clearly a contact effect of the first granite 

 sheets, here -with vertical attitude. Beyond, they show 

 evidences of being part of an injected and intensely 

 altered batholithic roof. The metamorphism, then, is 

 here primarily related to the presence of magmas, but 

 is secondarily related to depth. Deformation is the 

 adventitious factor which, has affected all the section and 

 produced cleavage with hydration in the upper and cooler 

 portions, cleavage with dehydration in those portions 

 which are deeper, hotter, and invaded by magmatic ema- 

 nations. 



The Section across Northwestern Connecticut. 



The writer has made a study of the geologic section on 

 the northern state line of Connecticut from the Green 

 Mountain anticlinorium, here represented by the southern 

 Berkshire Hills, w^estward across the Taconic syncli- 

 norium into New York State. The Laurentian Becket 

 gneiss, with its included metasediments, and the Lower 

 Cambrian Dalton schist outcrop in the anticlinorium. 

 The rocks are overturned and overthrust upon the Stock- 

 bridge marble of Cambro-Ordovician age. This outcrops 

 in the picturesque Housatonic Valley, here some eight 

 miles in breadth and marking the structural limb between 

 anticlinorium and synclinorium. The axis of the latter 

 holds synclines of the resistant Berkshire schist, of upper 

 Ordovician age. The structures throughout are intensely 

 deformed by minor and major folds and by mashing. 

 The foliation planes are in general inclined eastward at 

 a dip of about 30°, showing an intense regional over- 

 thrusting. 



