16 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



containing a hydrated mica or a green chloritic mineral, whicli is at times 

 certainly derived from garnet ; or the series is developed as a whetstone- 

 schist — that is, as a thin-bedded, finely biotitic, arenaceous quartzite. It is 

 the upper sei'icite-schist, or Savoy schist. ((/) A mica-schist, in great thick- 

 ness at times, exactly like the finely corrugated biotite-spangled garnet- 

 schist of Conway and Goshen, as in Northfield jMountain, on the Shutesbury- 

 New Salem line, and in Monson. Usually it is a coarse, barren, muscovite- 

 biotite-schist, like most of the Conway schist, but always without limestone, 

 which seems to be replaced by hornblende-schists. It is the equivalent of 

 the Goshen schist and the Conway schist. It is named after the more 

 imjDortant member and the one it most resembles — the Conway schist. 



Instead of appearing in broad areas, succeeding each other from west 

 to east — i. e., from below up, as they do in the western hills — the schists 

 appear here in sharply compressed synclines which run across the State, 

 disjointed by faults and thrown into confusion by the presence of eruptive 

 rocks. Four such great synclines can be traced across the State, within 

 the limits of the three river c(»unties, though their identity is disguised 

 by the fact that metamorphic changes superinduced upon original variations 

 in composition have varied greatly Ijoth in kind and degree. One may 

 esjDecially adduce the fibrolitization which has progressively affected the 

 mica-schist from west to east and from north to south. 



For the reasons given above it will be more convenient to follow a 

 geographical rather than a geological order in the discussion of the eastern 

 schists and to take up the different synclines in succession. 



(tENERAL comparative section of rocks in MASSACHUSETTS. 



In the first column of the accompanying general section I have placed 

 the section for northwestern Massachusetts, as determined by the labors of 

 Pi'ofessors Pumpelly, Dale, and Wolff, ^ though they must not be held 

 responsible for the exact parallelism here attempted. The distinction 

 between the Becket conglomerate-gneiss below and the Cheshire quartzite 

 can not here be always maintained, and the quartzite graduates both 

 laterally and vertically into the limestone. 



The area east of the Connecticut and extending slightly into Worcester 



' Geology of the Green Mountains in Massachusetts: Mon. U. S. Geol. Survey, Vol. XXIII, 1894. 



