Suture (geology)

In structural geology, a suture is a joining along a major fault zone, of separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories. The suture is often represented on the surface by an orogen or mountain range. ^[1]

Overview

In plate tectonics, sutures are the remains of subduction zones, and the terranes that are joined are interpreted as fragments of different palaeocontinents or tectonic plates.

Outcrops of sutures can vary in width from a few hundred meters to a couple of kilometers. They can be networks of mylonitic shear zones or brittle fault zones, but are usually both. Sutures are usually associated with igneous intrusions and tectonic lenses with varying kinds of lithologies from plutonic rocks to ophiolitic fragments.^[2]

An example from Great Britain is the Iapetus Suture which, though now concealed beneath younger rocks, has been determined by geophysical means to run along a line roughly parallel with the Anglo-Scottish border and represents the joint between the former continent of Laurentia to the north and the former micro-continent of Avalonia to the south.^[3] Avalonia is in fact a plain which dips steeply northwestwards through the crust, underthrusting Laurentia.

Paleontological use

When used in paleontology, suture can also refer to fossil exoskeletons, as in the suture line, a division on a trilobite between the free cheek and the fixed cheek; this suture line allowed the trilobite to perform ecdysis (the shedding of its skin).

References

^ There is a "difference between the geophysical and geological definition of suture zones and terrane boundaries. The geophysical definitions are generally based upon the integration of a physical response over the thickness of the crust, whereas the geological definition is almost always as a line or zone at the Earth's surface." Harris, Anthony L. and Fettes, D. J. (1988) The Caledonian-Appalachian orogen published for the Geological Society by Blackwell Scientific Publications, Oxford, England, page 4, ISBN 978-0-632-01796-6
^ Grotzinger, John P.; Thomas H. Jordan (2014). Understanding Earth (7th ed.). New York. ISBN 978-1-4641-3874-4. OCLC 884299180.{{cite book}}: CS1 maint: location missing publisher (link)
^ Oliver, G. J. H.; Stone, P. and Bluck, B. J. (2002) "The Ballantrae Complex and Southern Uplands terrane" pp. 167–200 In Trewin, N. H. (editor) (2002) The Geology of Scotland The Geological Society, London, page 191, ISBN 978-1-86239-126-0

Sources

Heron, P., Pysklywec, R. & Stephenson, R. Lasting mantle scars lead to perennial plate tectonics. Nat Commun 7, 11834 (2016). https://doi.org/10.1038/ncomms11834

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[1] There is a "difference between the geophysical and geological definition of suture zones and terrane boundaries. The geophysical definitions are generally based upon the integration of a physical response over the thickness of the crust, whereas the geological definition is almost always as a line or zone at the Earth's surface." Harris, Anthony L. and Fettes, D. J. (1988) The Caledonian-Appalachian orogen published for the Geological Society by Blackwell Scientific Publications, Oxford, England, page 4, ISBN 978-0-632-01796-6

[2] Grotzinger, John P.; Thomas H. Jordan (2014). Understanding Earth (7th ed.). New York. ISBN 978-1-4641-3874-4. OCLC 884299180.{{cite book}}: CS1 maint: location missing publisher (link)

[3] Oliver, G. J. H.; Stone, P. and Bluck, B. J. (2002) "The Ballantrae Complex and Southern Uplands terrane" pp. 167–200 In Trewin, N. H. (editor) (2002) The Geology of Scotland The Geological Society, London, page 191, ISBN 978-1-86239-126-0

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v t e Structural geology
Underlying theory	Deformation mechanism Lamé's stress ellipsoid Mohr–Coulomb theory Mohr's circle Overburden pressure Rock mechanics Strain Strain partitioning Stress Stress field Tension
Measurement conventions	Brunton compass Inclinometer Orthographic projection Rake Stereographic projection Strike and dip
Large-scale tectonics	Accretionary wedge Allochthon Autochthon Back-arc basin Continental collision Convergent boundary Décollement Divergent boundary Extensional tectonics Fault block Fenster Fold and thrust belt Fold mountains Foreland basin Graben Half-graben Horse Horst Horst and graben Intra-arc basin Inversion Klippe List of tectonic plate interactions Mélange Mountain formation Nappe Obduction Orogeny Passive margin Plate tectonics Pull-apart basin Rift valley Rift Saddle Strike-slip tectonics Structural basin Suture Syneclise Terrane Thick-skinned deformation Thin-skinned deformation Thrust tectonics
Fracturing	Columnar jointing Dike Exfoliation joint Fissure Joint Vein
Faulting	Asperity Cataclasite Cataclastic rock Detachment fault Disturbance Fault friction Fault mechanics Fault scarp Fault trace Thrust fault Transfer zone Transform fault
Foliation and lineation	Cleavage Compaction Crenulation Fissility Oblique foliation Pressure solution Rock microstructure Slickenside Stylolite Tectonic phase Tectonite
Folding	Anticline Chevron Detachment fold Dome Homocline Monocline Syncline Vergence
Boudinage	Competence
Kinematic analysis	3D fold evolution Paleostress inversion Paleostress Section restoration
Shear zone	Mylonite Pure shear Shear
Category