2 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



quarters miles long nearly at right angles to the strike of the 

 foliation and gives the longest continuous section of the schist in 

 the State of Connecticut. 



The Hartland formation as exposed in this state was described 

 in some detail by Rice and Gregory.^ They state on page 97: 

 "The rock is everywhere a mica schist of definable character, but 

 exhibits great variation in texture, composition, and field appear- 

 ance. Its aspect has been rendered still more complicated by the 

 intrusion of igneous rock on a large and a small scale. Where 

 least affected by intrusion, the rock appears as a highly fissile 

 schist ... In color it ranges from clear metallic muscovite in 

 West Granby, to a black biotite mixed with graphite further 

 south." Garnet is said to be almost always present and cyanite to 

 be scattered sparingly throughout almost the whole extent of the 

 schist, while staurolite is only locally developed. 



The general description summarized above fits the Hartland of 

 this section in a broad way but there is one very important dif- 

 ference. There are two distinct facies of schist exposed in the 

 tunnel and in the neighboring outcrops, namely a fissile, lustrous 

 schist corresponding to the above description, and a quartz schist 

 of totally different aspect. The latter type is a greenish white 

 to brown or bronze rock which cleaves along planes due to the 

 development of mica in bands but shows a great deal of quartz 

 when broken across the cleavage. The two types represent orig- 

 inal differences in composition, since they alternate as do sedi- 

 mentary strata, and first one and then the other will form the 

 dominant rock. 



The base of the Hartland (Hoosac) schist exposed along 

 the eastern edge of the Green Mountain anticlinorium in Mas- 

 sachusetts is a coarse garnetiferous mica gneiss. It rests 

 unconformably upon the underlying rocks and is overlain by a 

 non-garnetiferous series of alternating sandy and micaceous 

 layers.^ Such a succession parallels the distribution of the series 

 in Connecticut where with a westerly dip, the eastern beds are 

 characteristically full of garnets while the upper layers, repre- 

 sented by the tunnel section, are prevailingly non-garnetiferous 

 quartz and mica schists. 



The structure of the series as a unit, the amount of repetition 

 by folding or by thrust faulting, are still undetermined. It is 

 believed that the detailed study of the surrounding areas, now 

 under way, will clear up much that is now in doubt. The evidence 

 available from this particular region will be discussed further 

 along. 



There are a number of outcrops of the quartz schist in the 

 area north of Morris and south of the tunnel line and again along 



^ Manual of the Geology of Connecticut. Conn. Geol. and Nat. Hist. Survey, Bull. 6, 

 pp. 96-100, Hartford, 1906. 



2 Joseph Barrell, unpublished typewritten manuscript. 



