Triassic Fault of Southern Connecticut. 487 



lenses, and here and there gives place to a sandstone 

 within a few feet of vertical distance. 



As shown by the accompanying map (fig. 1), the fan- 

 glomerate never extends more than abont half a mile 

 from the fault plane. To the west it interfingers with 

 the sandstones and conglomerates. Long lenses of the 

 fanglomerate run out into the finer rocks. It outcrops 

 at a number of different localities, some of which may 

 have been originally continuous. The actual thickness 

 of each mass is difficult to determine, two or three hun- 



Fig. 2. 



Jforth 



Pond 

 Rock 



LAKE 



Fig. 2. — Generalized section from Beacon Hill to the South end of Pond 

 Rock, showing the gradation from fanglomerate to shale with increasing 

 distance from the Great Fault. 



dred feet being the maximum thickness actually 

 measured. The fanglomerate is found below the lower 

 basalt flow, immediately below the main sheet, below the 

 upper basalt flow, and above all the flows. The rocks 

 close to the Great Fault are all concealed in the horizons 

 much below the lowest trap sheet, and therefore there is 

 no direct evidence as to whether or not fanglomerates 

 exist in them or not. The rocks immediately above the 

 main sheet are usually fine-grained even close to the 

 Great Fault. 



The pebbles of the fanglomerate consist of all the 

 crystalline rocks found to the east of the Great Fault, 

 pegmatites, masses of vein quartz and feldspar several 

 inches long, large bowlders of basalt, some of which are 

 vasicular and highly angular, and pebbles of the quartz 

 lode. Sometimes abundant pebbles of a rock are found 

 in the fanglomerate, though there is no such rock in the 

 vicinity on the crystalline side of the fault plane. This 

 may mean that the rock once occurred east of the fault, 



