sinistral adj

1 of or on the left; "a sinistral gastropod shell with the apex upward has its opening on the left when facing the observer"; "a sinistral flatfish lies with the left eye uppermost" [ant: dextral]

2 preferring to use left foot or hand or eye; "sinistral individuals exhibit dominance of the left hand and eye"

English

Adjective

1. Of, facing, on on the left side.
2. Left-handed.
3. Having the whorls of the spire revolving or rising to the left; reversed; -- said of certain spiral shells.

Synonyms

• sinistrous

Antonyms

• dextral

Derived terms

• sinistral fault
• sinistral fold

Related terms

• sinister

References

This article is about the geologic usage, for human physiology usage see the articles laterality.

The terms sinistral and dextral (or left-handed and right-handed) are also used to describe the direction of coiling in gastropod shells.

The terms sinistral and dextral refer to the horizontal movement of blocks on either side of a fault or the sense of movement within a shear.;Dextral or right lateral movement: 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.

Naming origin

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

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 dikes
• 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

Examples

See also

• Fault (geology)
  • Thrust fault
• Shear (geology)
• Transform boundary

References

• Schlumberger Oilfield Glossary

backhand, backhanded, circuitous, counterclockwise, deflectional, deviant, deviative, devious, digressive, divagational, divergent, excursive, indirect, larboard, left, left-hand, left-handed, left-wing, left-wingish, levorotatory, liberal, near, nigh, oblique, port, radical, side, sidelong, sinister, sinistrocerebral, sinistrocular, sinistrogyrate, sinistromanual, sinistrorse, southpaw