DEFORMATION ALONG THE BOUNDARY. 521 



movement on the fault-plane should be discovered if possible. The 

 relation of the fault to the existing topography is an important matter, 

 this being frequently so prominent that it becomes the chief guide in 

 tracing the fault-line in a preliminary survey. 



The surface elements of a fault having been determined, there are 

 elements connected with its past history that need attention. Its date 

 of occurrence, its rate of movement, its cause, including the reasons for 

 its location in one place rather than in another ; its effect on the topog- 

 raphy at the time of its production, and its effect on the subsequent pro- 

 cesses of denudation, ending with the development of the existing 

 topographic features. 



It is hardly necessary to state that as a rule there is no opportunity for 

 the determination of most of these elements of a fault ; yet none the less 

 should they be borne in mind and patiently searched for. The recent 

 discovery of the long hidden "secret of the highlands " of Scotland, of 

 the overthrust faults in the southern Appalachians, and of the mechani- 

 cal conditions of the processes of faulting in folded structures are strong 

 encouragements to the success of similar studies elsewhere. 



Deformation along the eastern Boundary of Connecticut Triassic. 



general account of the eastern boundary. 



We have been led to the conclusion that the entire eastern boundary 

 of the Triassic formation in Connecticut is defined by fault-lines — a com- 

 bination of several intersecting' faults, rather than a single irregular fault. 

 As indicated on the map, figure 1, the inferred faults ma}^ be divided into 

 two*sets, those of one set trending about nortli and south, and represented 

 by three members ; those of the other set trending northeast and south- 

 west, and including two members. All five faults are believed to extend 

 beyond the parts of the border line that they determine into the area of 

 the crystalline or Triassic rocks. In the following description the faults 

 will be referred to by numbers, as on the maj) ; the first (with a rather 

 irregular course), third and fifth belonging to the meridional set ; the 

 second and fourth belonging to the oblique set. The four angles in the 

 border line, formed at the successive crossings of the five faults, are dis- 

 tinctly marked in the field, and will be referred to as the Glastonbury, 

 Highland Park, Vernon, and Rockville corners. 



EVIDENCES OF FAULTING ALONG THE BOUNDARY. 



Absence of direct Evidence. — With trifling exceptions, referred to below, 

 the lines and planes of the bordering faults are nowhere visible, either 

 along the ])oundary of the formation or along their extension elsewhere. 

 Within the Triassic area certain small branch faults associated with the 

 ftiults of the oblique set are exposed in quarries and streams, but none 



