
170 STRUCTURAL AND FIELD GEOLOGY 
developed, these frequently occupy lines of dislocation, which 
intersect at various angles. In such regions, therefore, the 
direction or trend of conjugate systems of faults and their 
relation to other similar systems have been very carefully 
studied, and we now know that the dislocations of a region 
may belong to two, three, or more periods of crustal 
disturbance. In Fig. 49 we have a model showing three 
lines of faulting, of which it is obvious that the dislocation 
a a must be the oldest, since it is shifted by the fault 4 0; 
while the latter in its turn is shifted by the fault ¢ c, which, 
therefore, must be the latest of the series. 
REVERSED FAULTS.—These faults are so termed because 
the hade is not in the direction of downthrow, as is the case 
with normal faults, but in the direction of upthrow. Lower 
or older rocks on one side of the dislocation have been thrust 
up over higher or younger rocks on the other side. The 
hade of a reversed fault, especially if it be a great displace- 
ment, is usually further inclined from the vertical than the 
hade of a correspondingly large normal fault. In some 
cases, indeed, an extensive reversed fault approaches 
horizontality. The rocks along the line of a reversed fault 
are often much compressed, crushed, and broken. Not 
infrequently, indeed, such a fault is marked throughout 
its whole extent by a band of shattered and crushed rock, 
forming what is termed a crush- or friction-breccia.* The 
rocks in the immediate proximity are also often more or 
less metamorphosed. 
The most notable reversed faults are met with in largest 
numbers in regions of highly folded and compressed rocks. 
They are of comparatively rare occurrence amongst horizontal 
and gently inclined strata. Like normal faults, they frequently 
bear an obvious relation to rock-folds, and their phenomena 
will be better understood if considered in connection with the 
general question of the origin of faults. 
TRANSCURRENT FAULTS OR TRANSVERSE THRUSTS.— 
It has been explained that the apparent horizontal shifting 
produced by normal faulting is really the effect of denuda- 
tion. Horizontal shifting of outcrops on the large scale, 
* If the stones are subangular or somewhat rounded, the fault-rock is 
sometimes termed crush-conglomerate. 


