CHAPTER III. 



GEOLOGICAL OUTLINE AND GENERAL COMPARATIVE 



SECTIONS. 



A long series of Arcliean outcrops runs from north to south across the 

 western portion of the high ground l^etween the Housatonic and the Con- 

 necticut valleys, and barely enters the western border of the area here 

 described. This high ground is the continuation of the Green Mountain 

 range across Massachusetts. Cambrian conglomerate-gneisses (Becket 

 gneiss) wrap around these patches of Archean, graduate westward into the 

 Stockbridge limestone, and dip eastward beneath the great sericite-schist 

 series, which may be placed parallel to the Berkshire and Greylock schists 

 on the west. These highly metamorphosed and much foliated sericite- 

 schists stand vertical in appressed folds for a long distance eastwai-d and 

 then go beneath the extensive graphitic schist series, coming up fartlier east 

 in anticlines from beneath the latter. A remarkable band of amphibolites, 

 with enstatite-bearing limestones and enstatite, pyi'oxene, and olivine rocks, 

 all largely changed to serpentine, and with emery, runs down the middle 

 of the sericite-schists. It seems to me possibly the equivalent of the Bel- 

 lowspipe limestone of Greylock ; and the Bolton limestone, farther east, is 

 upon about the same horizon. The upper series of graphitic schists (the 

 Goshen and the Conway schists) is less metamorphosed, and shows much 

 of the original lamination, though masked by cleavage and foliation. It 

 contains many beds of limestone in every stage of change to amjohibolite. 

 It is a graphitic musco\'ite-schist, abounding in garnet, staurolite, and 

 transverse spangles of biotite. It graduates into the corrugated and 

 cleaved Leyden argillite (phyllite) along- the eastern border of the elevated 



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