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Transtension is the state in which a rock mass or area of the Earth's crust experiences both ''extensive'' and ''transtensive''
''Releasing bends'' are transtensional structures that form where the orientation of a strike-slip fault becomes oblique to the regional slip vector causing local extension (such as a right stepping bend on a right-lateral fault). They also form where two segments of a strike-slip fault overlap, and the relay zone between the segments experiences transtension. Releasing bends often form negative flower structures or pull-apart basins. Geologists may also refer to a releasing bend as a right bend.
shear
Shear may refer to:
Textile production
*Animal shearing, the collection of wool from various species
**Sheep shearing
*The removal of nap during wool cloth production
Science and technology Engineering
*Shear strength (soil), the shear strength ...
. As such, transtensional regions are characterised by both extensional structures ( normal faults, graben
In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults.
Etymology
''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...
s) and wrench structures (strike-slip fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
s). In general, many tectonic regimes that were previously defined as simple strike-slip shear zones are actually transtensional. It is unlikely that a deforming body will experience 'pure' extension or 'pure' strike-slip.
Transtensional shear zones are characterized by the co-existence of different structures, related to both strike-slip shear and extension. End member structures include pure strike-slip faults and purely extensional ("normal") dip-slip fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tecton ...
s. Faults which have components of both (termed 'oblique' slip faults) are abundant.
Releasing bend
''Releasing bends'' are transtensional structures that form where the orientation of a strike-slip fault becomes oblique to the regional slip vector causing local extension (such as a right stepping bend on a right-lateral fault). They also form where two segments of a strike-slip fault overlap, and the relay zone between the segments experiences transtension. Releasing bends often form negative flower structures or pull-apart basins. Geologists may also refer to a releasing bend as a right bend.
Transtensional regions
*Dead Sea
The Dead Sea ( he, יַם הַמֶּלַח, ''Yam hamMelaḥ''; ar, اَلْبَحْرُ الْمَيْتُ, ''Āl-Baḥrū l-Maytū''), also known by other names, is a salt lake bordered by Jordan to the east and Israel and the West Bank ...
Kearey, Philip and Frederick J. Vine, ''Global Tectonics,'' Blackwell Science, 2nd ed., 1996, pp. 131-133
* Salton Sea
The Salton Sea is a shallow, landlocked, highly saline body of water in Riverside and Imperial counties at the southern end of the U.S. state of California. It lies on the San Andreas Fault within the Salton Trough that stretches to the Gulf o ...
* Sea of Marmara
The Sea of Marmara,; grc, Προποντίς, Προποντίδα, Propontís, Propontída also known as the Marmara Sea, is an inland sea located entirely within the borders of Turkey. It connects the Black Sea to the Aegean Sea via the ...
on the North Anatolian Fault
The North Anatolian Fault (NAF) ( tr, Kuzey Anadolu Fay Hattı) is an active right-lateral strike-slip fault in northern Anatolia, and is the transform boundary between the Eurasian Plate and the Anatolian Plate. The fault extends westward fro ...
* Vienna Basin Royden, Leigh H., The Vienna Basin: a Thin-Skinned Pull-Apart Basin ''in'' N. Christie-Blick and K.T. Biddle (eds.), ''Strike-Slip Deformation, Basin Formation, and Sedimentation''. SEPM Special Publications, 37.
See also
* Pull-apart basin *Rift
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics.
Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...
* Strike-slip tectonics
Strike-slip tectonics or wrench tectonics is the type of tectonics that is dominated by lateral (horizontal) movements within the Earth's crust (and lithosphere). Where a zone of strike-slip tectonics forms the boundary between two tectonic plates, ...
* Structural geology
Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover informatio ...
* Transpression
In geology, transpression is a type of strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear. It is generally v ...
References
Structural geology {{tectonics-stub