EVIDENCES OP FAULTING. 529 



the crystalline plateau ; therefore its foundation plane is more than 600 

 feet below the plateau surface. The fact that a fault of this value could 

 throw down the foundation plane to its present position indicates that, 

 as a maximum amount, less than 1,400 feet (2,000 — 600 -\-) of crystal- 

 line rock in the vicinity of South Glastonbury have been eroded since 

 Triassic times. Correspondingly, the Triassic foundation plane must be 

 less than 1,400 feet below the present Triassic surface, if it be considered 

 that only a small amount has been eroded from the crystallines to pro- 

 duce the present plateau. 



But how far east does the influence of the northeast fault go ? We 

 should suppose until the angle of slope of the foundation plane brought 

 the undisturbed sedimentary Triassic contact to the surface of erosion. 

 This would doubtless be at no great distance, for the coarseness of the 

 conglomerates along the eastern marginal line indicates nearness to a 

 Triassic shore ; but another meridional fault, number 3, with upthrow 

 on the east, crosses the old basin and uplifts the foundation plane so 

 that the Trias has been eroded, and gives a fault margin from Highland 

 Park to Vernon instead of a sedimentary contact farther east. Can any 

 idea of the value of this fault (number 3) be obtained? It must have a 

 minimum throw equal to the distance of the Triassic foundation plane 

 below the Triassic surface plus the elevation of the highest part of the 

 adjacent crystalline plateau above the Triassic surface ; the latter eleva- 

 tion is 600 feet; the former distance is between and 1,400 feet. The 

 minimum is therefore over 600 feet; the maximum might seem to be 

 indefinite, but the next fault helps to define it as less than 2,400 feet. 



Our combination of faults has carried us to Vernon, where fault number 

 3 is supposed to continue northward, and should have crystallines along 

 its east side. As in the case of number 1, at South Glastonbury, the 

 Trias appears instead, this time brought down by a fault of about 1,000 

 feet. If a throw of this value can bring down the Triassic foundation 

 plane below the present surface, the maximum throw of fault number 3 

 must have been less than 2,400 feet (1,000 -f 1,400 — ). 



As l^efore, we should follow eastward to find the line where the Tri- 

 assic sedimentary contact should come to the surface, but before it is 

 reached Ave come to another north-and-south fault, number 5. This line 

 bounds the Trias even into Massacluisetts, so that a sedimentary contact 

 on the eastern margin of the Connecticut Trias cannot be found at the 

 surface. For this last fault we can only assign a minimum value of 900 

 feet plus, which is something more than the difference in elevation be- 

 tween the levels of the Triassic surface and the highest points of the 

 crystalline plateau. If we may judge by erosion, brecciation and meta- 

 morphism, this line was one of greater dislocation than number 3. 



