520 DAVIS AND GRISWOLD BOUNDARY OF CONNECTICUT TRIASSIC. 



ELEMENTS OF A FA ULT. 



When the field worker is driven to believe that a fault traverses his 



district, it is an aid to further 

 study to have clearly in mind 

 all the facts that should be de- 

 termined before the whole his- 

 tory of the fault is unravelled, 

 just as the astronomer on dis- 

 covering a comet is aided in 

 his next work by knowing just 

 what facts must be determined 

 in order that the movements of 

 the comet can be recalled or 

 predicted. These facts are called 

 the elements of the comet, and 

 the same term may be profita- 

 bly applied to faults. Regard- 

 ing faults, it is desirable to search 

 first for such facts as may be vis- 

 ible at the surface of the earth. 

 Chief among these is the fault- 

 line, as indicated by the margins 

 of adjacent formations. It may 

 be straight or curved, simple or 

 branching ; it should be followed 

 from end to end. Occasionally 

 the fault-plane itself is locally 

 visible in streams, cliffs or cuts. 

 When possible, the hade or de- 

 parture of the plane from the 

 vertical should be determined. 

 This may be locally accom- 

 plished where the plane .is di- 

 rectly visible. It is sometimes 

 determined in a larger way when 

 the line of the fault leads over 

 hills and valle3^s. The mechan- 

 ical character of the fault should 



Yia^...X.-Tke Connecticut Valley Trio ssic Area. ^^ gtudicd aS indicated by the 



features of the fracture, when visible, or by the minor deformations in 

 adjoining rock masses. The displacement caused by the faulting should 

 be measured at various points along the fault-line, and the direction of 



