ORIGIN OF THE TRIASSIC TROUGH OF CONNECTICUT 697 



from the eastern to the western side of the valley.' The data 

 concerning the strikes and dips within the Connecticut trough 

 have never been assembled. Professor Davis' general statement 

 quoted above would lead one to suppose, however, that there is 

 an increase in the dips from the eastern toward the western side 

 of the depression. 



4. Pebbles in the upper conglomerates at the eastern border of 

 the basin are known to be similar to rocks exposed at the very edge 

 of the eastern upland. This condition is especially true near Lake 

 Quonnipaug in Durham, Connecticut. East of the lake a chlorite 

 schist, which is not common within the metamorphic rocks of the 

 upland, outcrops for a mile or two. West of the lake the coarse 

 "fan-glomerates" are filled with pebbles of this rock. The evi- 

 dence indicates that the eastern limit of the Newark formation is 

 at its ancient boundary, as Barrell's hypothesis would postulate, 

 and that the basin sediments never extended over the eastern up- 

 land. If the eastern and marginal fault developed after the period 

 of sedimentation, the chlorite schist at Lake Quonnipaug could 

 not have been exposed to erosion at the time the "fan-glomerates" 

 were being deposited. 



5. The abundant development of those rocks so aptly named 

 "fan-glomerates" by the western geologists along the eastern 

 side of the basin is, in itself, strong evidence of the early initiation 

 of faulting movements along this boundary. Such conglomerates 

 are common throughout the exposed thickness of the Totoket block, 

 but are not known on the western side of the valley.^ 



6. Finally, there is good evidence of the localization of vulcanism 

 along the eastern fault line long before the end of the period of 

 deposition within the basin. The writer has recently discovered a 

 volcanic neck, in the southern part of Durham, north of Totoket 

 Mountain, which lies within a stone's throw of the eastern fault 

 margin. 



' Excessive dips to the east are known near the eastern boundary fault. They 

 are in the opposite direction from the drag dips which one would expect in this 

 vicinity and have not been explained. 



^ Cf. C. R. Longwell, Amer. Jour. Sci., IV (1922), 234-35. 



