No. 40] GEOLOGY OF SHEPAUG TUNNEL 21 



the main highway west from Morris to Lakeside, south of Bantam 

 Lake. The outcrops of the latter set are intersected across the 

 strike of the foHation by the road cuts and show their quartzite 

 character but, if examined along the foliation planes, they closely 

 resemble the mica schist type. It is apparently this series of 

 outcrops coupled with several similar ones occurring near Bantam 

 village and at 'The Jams" in the Bantam River, both north of 

 Bantam Lake, that caused the area of Poughquag quartzite under- 

 lying Bantam Lake and stretching to the south of it to be placed 

 on the Preliminary Geological Map. The exposures underground 

 show that the quartz schist south of the lake is a part of the Hart- 

 land series and that that to the north represents fragments of the 

 Hartland included in and metamorphosed by the diorite to a 

 greater degree than the rest of the formation. 



In its first 6500 feet west from the outfall end, the tunnel cuts 

 a monotonous repetition of quartz and mica schist diversified only 

 by the prevalence of first one and then the other type and by the 

 varying number of intrusions of granite and pegmatite. 



The mica schists are uniformly fine grained with smooth shiny 

 surfaces and a micaceous luster. There is little fine crumpling 

 and, where the rock is entirely free from injected igneous matter, 

 it has almost the luster of a phyllite. Under the microscope this 

 rock appears as an aggregate of biotite, muscovite, and quartz with 

 subsidiary cloudy plagioclase, rare, rounded grains of apatite and 

 variable amounts of pyrite. The proportion of biotite to mus- 

 covite varies and quartz ranges from less than one-half the volume 

 of the rock in the true mica schist to more than seventy per cent 

 in the quartz schist. The latter has the same mineral composition 

 as the mica schist except for the greater amount of quartz. 



The foliation of both types is due to the development of discon- 

 tinuous bands of orientated mica laths. The space between these 

 bands is filled by medium-grained quartz partly elongated parallel 

 to the mica and partly in smaller equidimensional grains. The 

 texture is crystalloblastic (Plate vi a). There is no sign of 

 granulation but there is an occasional slight tendency for the mica 

 to be wrapped around the larger elongated quartz crystals. 



This section of the schist has been cut by many pegmatite dikes 

 and a lesser quantity of granite dikes and quartz veins. It is 

 generally true that the intrusives parallel the foliation but some 

 intersect it and all lack the foliation characteristic of the other 

 rocks so that they must date from near the end of the period of 

 folding or subsequent to it. The igneous rocks inject the schist on 

 a small scale as well and locally turn it into a coarse-grained gneiss. 



The next one thousand feet of the tunnel pass through an 

 interesting series of quartzites and sericite, hornblende, and garnet 

 schists. The first variant to be encountered is a ten-foot bed of 

 soft, white, lustrous muscovite schist. It differs from the normal 

 mica schist, when examined under the microscope, only by the 



