530 DAVIS AND GRISWOLD — BOUNDARY OF CONNECTICUT TRIASSIC. 



In figure 2 a diagrammatic representation is given indicating our con- 

 ception of the complicated part of the boundary line, looking at the dis- 

 trict from the north, so that all the steps are in full view, and picturing 

 the contact planes, both of sedimentation and faulting, of the two forma- 

 tions. The solid block may be considered as composed entirely of old 



crystalline rocks ; an imaginary 

 cap fitting this block would rep- 

 resent the original Trias. The 

 numbers given to the different 

 fault-lines are indicated on the 

 diagram. 



FINAL CONSIDERATIONS. 



The hypothesis of a combina- 

 tion of faults is thus seen to 

 correspond with the facts of dis- 

 tribution of formations and of 

 faults. No evidence is known 

 that contradicts the hypothesis 

 in any way ; it may seem weak 

 because of a partial lack of evi- 

 dence. It may at first thought 

 be considered a suspicious acci- 

 dent that the level of the pres- 

 ent erosion surface should fall 

 so nicely between the limits 

 within which it is possible to 

 get the evidence revealed in the district between South Glastonbury and 

 Rockville ; yet one can see on considering a detailed map that were the 

 erosion surface relatively several thousand feet lower or higher than it 

 now io the demonstration of the structure would be equally clear. That 

 the hypothesis offers a rational explanation of the widening of the 

 Triassic to the north is in its favor. 



A point of interest connected with the demonstration is that the basal 

 members of the Trias are brought up on the eastern side of the basin. 

 It of course occurs to one to identity these rocks with those on the west- 

 ern side. As yet no characteristic beds are known on either side, so 

 comparison cannot be made. 



Figure 2.— Stereogram of Cross-Faults of the Eastern 

 Boundary of the Connecticut Trias. 



