Dextral

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Dextral or right lateral refers to the horizontal movement of blocks on either side of a geological fault or the sense of movement within a shear.

Movement is dextral (right handed) if the block on the other side of the fault moves to the right, or if straddling the fault the right side moves toward the observer.

Dextral gains its origins from the Latin "dexter" for right-handed. The opposite sense of movement sinistral gains its name from the Latin "sinister" for left-handed.

Schematic illustration of the two strike-slip fault types. The view is of the Earth's surface as from space.

[edit] Identifying sense of throw

Identifying the sense of throw of a fault or the sense of shear can be achieved via several methods:

• Mappable offset of rock units
• Offset of visible bedding, cross cutting dykes
• Folding of strata proximal to a fault caused by frictional drag
• Shear sense indicators in sheared rocks such as
  • Mica fish
  • Extensional veins
  • Shear deflections and stair-stepping of shear folia (figure 1, figure 2).

Figure 1.
Boudinaged jasperoid in sheared basalt, Fortnum Gold Mine, Australia. Example of dextral shear.

Figure 2.
Boudinaged quartz vein in dextral shear foliation, Starlight Pit, Fortnum Gold Mine, Western Australia.

[edit] See also

• Faults
• Thrust fault
• Sinistral
• Transform boundary
• Shearing

[edit] References

• Schlumberger Oilfield Glossary