Faulting—Chapter 13
Faults=fractures or cracks in rock along which movement
has occurred parallel to the fracture surface. Caused by
tensional, compressional, or shearing forces
Basically, there are 3 types of faults:
Normal
Reverse
Strike Slip
Normal Faults: Tensional forces; hanging wall moves
down with respect to footwall.
See figures 13.1, 13.2, 13.3 in lab manual
Reverse Faults: Compressional forces; hanging wall
moves up with respect to footwall.
See figures 13.4a and 13.4b in lab manual
Strike-Slip Faults: Shearing forces; fault blocks slide
parallel to the strike or trend of the fault surface. Ex.-San
Andreas fault, CA. See Figure 13-5 in lab manual
Folding AND Faulting—See figure 13.6 in lab manual. In
this example, a plunging syncline has been faulted.
Complex, but CAN be understood
Rules for interpreting geologic structures:
1. The upthrown side of a normal or reverse fault will be
eroded to the level of the down thrown side in time.
2. Contact lines and associated rock formations always
shift in the direction of dip as the land surface is
lowered by erosion
Unconformity—surface that represents a break in earth
history. 3 types:
 Disconformity—type of unconformity where erosion
surface is parallel to younger rocks above and older
rocks below; see fig. 13-7 in lab manual
 Angular unconformity—results from erosion of
deformed sedimentary rock followed by deposition of
younger, horizontal sedimentary rock; see fig. 13-8 in
lab manual
 Non-conformity—results from erosion of older
igneous/metamorphic rock followed by deposition of
younger, horizontal sedimentary rock; see fig 13-9 in
lab manual