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



FAULTS 



There are a number of faults exposed in the underground 

 section. Most of them are small normal faults with a relatively 

 flat westerly dip. Only in one instance could an exact measure 

 of the throw be made. Two vertical faults with the downthrow 

 block on the west cause the repetition of two narrow calcareous 

 bands of the schist with a combined throw of one hundred seventy 

 feet. The strike of all these small faults averages nearly north- 

 south. 



About one mile east of the eastern corner in the tunnel there is 

 a fault of some magnitude. It strikes north sixty-four degrees 

 east and dips twenty-four degrees north. Several feet of clay 

 gouge accompany the fault and the foot wall rock is badly shattered 

 for a distance of nearly one hundred feet. Due to the fractured 

 character of the rock, it is impossible to determine the direction 

 of the throw. There is no surface expression of the line of 

 weakness nor can the fault affect the calculation of the minimum 

 thickness of the schist given above since it lies to the west of 

 the area considered. 



METAMORPHISM OF THE HARTLAND SCHIST 



The Hartland schist, in common with the other rocks of the 

 region, has undergone a rather complicated set of changes. An 

 original series of normal sedimentary strata made up of sandstone, 

 shale, and relatively rare calcareous layers was so compressed by 

 forces acting in a general east- west direction that the beds were 

 greatly folded and overturned over considerable areas. Intrusions 

 of granite on a regional scale accompanied the folding both as 

 stocks several miles in diameter and as dikes and fine injections 

 of granite and pegmatite. The stocks are in part strongly gneis- 

 soid with a cataclastic texture showing that they preceded some of 

 the folding, but the dikes, probably later offshoots from the same 

 magma, show no sign of mashing. 



The schist is completely recrystallized and, in general, at least 

 throughout the area here discussed, the foliation is parallel wath 

 the original bedding. There is no granulation of the minerals 

 and no suggestion of straining after the crystalloblastic texture 

 developed. 



The area of Hartland schist covered by this report is entirely 

 free from large granitic intrusions. To the east of this section 

 the Thomaston granite and the pegmatite dikes form a large pro- 

 portion of the surface outcrops and the schist is very thoroughly 

 cut up and intimately penetrated by the igneous rocks. The 

 granites nearly give out in the tunnel region but the pegmatites 

 persist in great numbers and locally penetrate the schist to such 

 an extent as to form a migmatite. 



A more complete study of the whole Hartland schist is needed 



