72 GEOLOGY OF OLD HAMPSHIRE COUXTY, MASS. 



filled with flattened lenses, placed with the bedding, of quartz and of quartz 

 and feldspar ; and from this point the road runs for nearh^ a mile through 

 an almost continuous cutting of the light-gray, flat-bedded hydromica- 

 schists belonging to the next series — the Rowe schists, which are without 

 accessory minerals of any kind and preserve a monotonous uniformity. 

 The dip is nearl}^ vertical, and the section line is nearly at right angles to 

 the strike. 



RELATION TO THE 15ECKET GNEISS. 



It has been already stated that at the brook junction east of Bancroft 

 station the change from the compact, flesh-colored, granitoid gneiss of the 

 Becket series below to the porphyritic hydromica-schist is abrupt. The 

 contact between the two is exposed for a good distance and is a fissure, the 

 rocks not being welded together, and the discordance in strike is consider- 

 able and in dip very large. There is certainly unconformity and probabl)" 

 faulting at this point, but the nearness of the point to the area where the 

 Becket gneiss is so in-egularly wrapped around the southern end of the 

 Hinsdale gneiss, and the fact that the Becket gneiss is peculiarly irregular 

 in structure clear up to the junction, make it possible that this unconformity 

 is only local, and at all events deprive it of a decisive weight in settling the 

 question of real unconformity. The junction can be well followed north 

 from the railroad to the center of Middlefield, and the .series retains exactly 

 its character, showing a great development of feldspathic hydromica-schists 

 and imperfect, sandy gneisses, and above these a much greater mass of 

 barren, gray, and green-blotched schists, belonging to the Rowe schists. 

 The transition between the two series — the gneiss and the feldspathic 

 schist — is best .studied between the Aallage and the Fair Grounds in Middle- 

 field ("enter. 



Just below the point where the roads join at M. Smith's, south of 

 the Fair Grounds, the Rowe hydromica-schist, while retaining exactly its 

 dip and strike (strike N. 10° E., dip 70° to 80° E.), its flat-fissile, schistose 

 appearance, its gray surface spotted with green, and the multitude of small 

 corrugated and twisted quartz lenses, becomes indistinctly porph3^ritic, the 

 feldspar here and there cementing together a group of sand grains. As one 

 goes lower (i. e., westerly) this alternates many times in thick and thin 

 beds with the common hycbomica-schist, often chloritic, until the beds 

 which strike through the Fair Grounds become a quite well-characterized 



