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

The gastropod shell is a seashell which is part of the body of a Gastropoda or snail. It is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage....
s.


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. Sinistral or left lateral movement: Movement is sinistral (left-handed) if the block on the other side of the fault moves to the left, or if straddling the fault the left side moves toward the observer. 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.

stral gains its origins from the Latin "sinister" for left-handed
Left-handed

Left-handedness is the preference for the left hand over the right for everyday activities such as Penmanship. Most left-handedness people exhibit some degree of ambidexterity....
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The terms sinistral and dextral (or left-handed and right-handed) are also used to describe the direction of coiling in gastropod shell
Gastropod shell

The gastropod shell is a seashell which is part of the body of a Gastropoda or snail. It is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage....
s.


Strike Slip Fault
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. Sinistral or left lateral movement: Movement is sinistral (left-handed) if the block on the other side of the fault moves to the left, or if straddling the fault the left side moves toward the observer. 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
Left-handed

Left-handedness is the preference for the left hand over the right for everyday activities such as Penmanship. Most left-handedness people exhibit some degree of ambidexterity....
. The opposite sense of movement dextral gains its name from the Latin "dexter" for right-handed
Right-handed

Someone who is right-handed will prefer to use this hand for everyday activities, such as Penmanship, maintaining Hygiene, cooking and so forth....
.

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
    Stratum

    In geology and related fields, a stratum is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers....
     proximal to a fault caused by frictional drag
  • Shear sense indicators
    Rock microstructure

    Rock microstructure includes the Texture of a rock and the small scale rock structures. The words "texture" and "microstructure" are interchangeable, with the latter preferred in modern geological literature....
     in sheared rocks such as
    • Mica fish
      Mica fish

      Mica fish are lenticular, elongate lozenge, parallelogram-shaped, or lens-shaped single mica crystals that are often used as shear sense indicators....
    • Extensional veins
      Vein (geology)

      In geology, a vein is a finite volume within a rock , having a distinct shape, filled with crystals of one or more minerals, which were precipitated from an fluid....
    • Shear deflections and stair-stepping of shear folia
      Foliation (geology)

      Foliation is any penetrative planar Fabric present in Rock . Foliation is common to rocks affected by regional metamorphism compression typical of orogeny....


Examples

Image:Skagit-gneiss-Cascades.jpg|Banded gneiss with dike of granite orthogneiss with sinistral shear Image:boudinage.jpg|Boudinage
Boudinage

Boudinage is a geological term for structures formed by extension, where a rigid tabular body such as a bed of sandstone, is stretched and deformed amidst less competent surroundings....
d jasperoid
Jasperoid

Jasperoid is a rare, peculiar type of Metasomatism alteration and occurs in two main forms; sulfidic jasperoids and hematitic jasperoids. True jasperoids are different from jaspillite, which is a form of metamorphosed chemical sedimentary rock, and from jasper which is a chemical sediment....
 in sheared basalt, Fortnum Gold Mine, Australia. Example of dextral shear Image:boudin_vein.jpg|Boudinaged quartz vein in dextral shear foliation, Starlight Pit, Fortnum Gold Mine, Western Australia

See also


  • Fault (geology)
    • Thrust fault
      Thrust fault

      A thrust fault is a type of Geologic fault, or break in the Earth's crust with resulting movement of each side against the other, in which a lower stratigraphic position is pushed up and over another....
  • Shear (geology)
  • Transform boundary