1. Autumn, of the current year
GLY 326 Structural Geology
Lecture 30
Reverse Faults
Autumn, of the current year

2. Dip-Slip Faults

4. Reverse faults:
Compression
Older strata on top of younger strata
Thrusts (horses and wedges)

5. Reverse faults:
In maps we mark them with a line with “teeth” indicating the hanging block.

7. So… where we can find compression?
(shortening)

8. At the subduction zones!!!

9. Orogenesis (building mountains)…. thrust geometry
(American Embassy in Santiago)

10. Thrust faults: Horses and Wedges
A thrust fault is a reverse fault in which the dip of the fault plane is very low… (<30o)

11. Keystone Thrust, Nevada
Paleozoic
Jurassic
(View to northwest)

12. HIMALAYAN FRONTAL THRUST
Himalayan Frontal thrust- active thrust slicing up foreland basin
Flat on ramp geometry here in poorly consolidated sediments

13. The McConnell thrust, Alberta.
View to North
The McConnell thrust, Alberta.
ramp

14. Example: Lewis Thrust Fault

15. Example: Lewis Thrust Fault
fenster
klippe

16. hanging wall
footwall

17. Lewis Thrust Fault (cont'd)
Source: Breck P. Kent
pre-Cambrian Limestone over
Cretaceous Shales!!!

19. Flat-ramp geometry in the Chilean Andes.

20. New thrusts initiate & propagate in direction of foreland:
new thrust develops “ahead” of old one
Hinterland
upper glide horizon
lower glide horizon
Foreland
Incipient second thrust
“piggy-backing”
Incipient third thrust
Hinterland and foreland: hanging and footwall in orogenesis

21. Some Rules For Thrust Faults
Thrusts cut ‘UP’ stratigraphic section in transport direction
(vergence)

22. continued forward propagation of thrusts produces duplex or imbricate fan:
roof thrust
Propagation ** *
sole thrust
horses
DUPLEX: all the horses together.

23. Three views of thrust system
“Wedge shape”

24. Duplex at Crows Nest Pass - Alberta
(At any scale)

25. Thrust sheets + imbricate fans + duplexes + folds
= thrust belt
Fold & Thrust Belt

26. Lewis Thrust Fault (reconstructed)

27. To visit: