This fault, at the leading edge of the Sevier Fold-Thrust Belt in southern Nevada, places Cambrian Bonanza King Formation (gray) over Jurassic Aztec Sandstone (pink).
Ramp Anticline, southern British Columbia, Canada.
Note the minor thrust fault immediately to the right of the hammer
STRIKE-SLIP FAULTS
Strike-slip faults involve motion which is parallel to the strike of the fault--frequently described as a "side-by-side" motion. Strike-slip faults are further described as "rightlateral" (dextral) or "left-lateral" (sinistral) depending if the block opposite the viewer moved to the right or left respectively. According to Anderson's model, both the maximum and minimum compressive stresses which drive the faulting are horizontal. Additionally, these stresses are oblique to the fault; the direction of maximum compressive stress is about 30 degrees from the fault strike. In the case of conjugate faults, the direction of maximum compressive stress bisects the acute angle .
Chief Mountain, the prominent peak on the right, consists of Precambrian rock in the hangingwall of the Lewis Thrust (red arrow). Cretaceous shale and sandstone, which occupy the footwall underlie the vegetated slopes. Chief Mountain is an example of a Klippe because it was isolated from the rest of the hangingwall by erosion
This thrust fault is approximately horizontal. Note the anticline in the hangingwall and the syncline in the footwall
Lewis Thrust fault. As viewed from Marias Pass, Glacier National Park, Montana. Looking N
Faults
Strike-slip faults
Transform Faults
Oblique slip faults
NORMAL FAULTS
Normal faults extend the crust in a direction perpendicular to the fault trace. Because the hangingwall moves downward, normal faults place younger rocks over older rocks. Normal faults may dip at a variety of angles, but they most typically dip between about 40 and 70 degrees. Some normal faults dip at angles as low as 10 degrees or less. These low-angle normal faults pose especially interesting problems for structural geologists.
Normal faults Reverse faults Strike-slip faults Oblique slip faults Transform Faults
FAULTS
By Zhu Qiang
• Normal faults Dip slip Faults • Reverse faults
Thrust faults and associated fold. Near Klamath Falls, OR
Reverse Fault. Death Valley, CA
Keystone Thrust. Red Rocks State Park, Nevada Thrust fault and folds. SW Wales, UK
STRIKE-SLIP FAULTS
Movement along strike-slip faults is horizontal.
Left-lateral
strike-slip fault Right-lateral strike-slip fault
Strike-Slip Faults
NORMAL FAULTS
Normal faults in felsic volcanic rock, Death Valley, California. Note the back-tilted layering.
This west-dipping normal fault places Quaternary Basalt (dark-colored) in hanging wall against on Eocene Claron Formation (red-colored, flat-lying rocks.)
Conjugate Normal Faults
Conjugate Normal faults, Death Valley, California Conjugate Normal faults, Canyonlands National Park, Utah
Normal faults are conjugate if they consist of two sets of faults which dip towards each other to intersect at an angle of approximately 60 degrees, and slipped concurrently. In these cases, the maximum principle compressive stress bisects the acute angle between the faults. In this example, the max. compressive stress is nearly vertical.
Horst and Graben
Horst and graben terrane, seen in the Basin and Range Province of the western U. S., is dominated by normal faults.
REVERSE FAULTS
Thrust and Reverse faults form by horizontal compressive stresses and so cause shortening of the crust. Because the hangingwall moves up relative to the footwall, most of these faults place older rocks over younger rocks. Younger over older relations can occur when previously deformed rocks are thrust faulted. Thrust faults typically dip at low-angles, between about 10-40 degrees. However, because thrust faults cut through stratigraphic sections as either ramps or flats, their orientations can vary considerably. Additionally, repeated slip on other faults and/or associated folding, can cause originally low-angle faults to rotate to steep
Green arrow points to fault. There, Precambrian rocks of the Belt Supergroup lie directly on top Cretaceous shale and sandstone
Klippe. Chief Mountain, Glacier National Park, Montana
Notice that this photo shows both right- and left-lateral faults. Because they intersect at an angle of about 60 degrees and slipped concurrently (determined from mutually cross-cutting relations not visible in this photograph), they define a conjugate set. Therefore, the maximum compressive stress is horizontal and bisects the acute angle between the faults; the minimum compressive stress is also horizontal and bisects the obtuse angle.