Orogen-parallel extension and oblique tectonics: The relation between stretching lineations and relative plate motions

Ellis, Michael A.; Watkinson, Anne

doi:10.1130/0091-7613(1987)15<1022:oeaott>2.0.co;2

Cited by 93 publications

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“…In addition, attempts to relate regional lineation patterns to plate motions (e.g. Shackleton & Ries 1984;Ellis & Watkinson 1987) may also be unwise in transpression zones.…”

Section: Discussionmentioning

confidence: 99%

Transpression and transtension zones

1998

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Transpression and transtension are strike-slip deformations that deviate from simple shear because of a component of, respectively, shortening or extension orthogonal to the deformation zone. These three-dimensional non-coaxial strains develop principally in response to obliquely convergent or divergent relative motions across plate boundary and other crustal deformation zones at various scales. The basic constant-volume strain model with a vertical stretch can be modified to allow for volume change, lateral stretch, an oblique simple shear component, heterogeneous strain and steady-state transpression and transtension. The more sophisticated triclinic models may be more realistic but their mathematical complexity may limit their general application when interpreting geological examples. Most transpression zones generate flattening (k < 1) and transtension zones constrictional (k > 1) finite strains, although exceptions can occur in certain situations. Relative plate motion vectors, instantaneous strain (or stress) axes and finite strain axes are all oblique to one another in transpression and transtension zones. Kinematic partitioning of non-coaxial strike-slip and coaxial strains appears to be a characteristic feature of many such zones, especially where the far-field (plate) displacement direction is markedly oblique (<20 ~ to the plate or deformation zone boundary. Complex foliation, lineation and other structural patterns are also expected in such settings, resulting from switching or progressive rotation of finite strain axes. The variation in style and kinematic linkage of transpressional and transtensional structures at different crustal depths is poorly understood at present but may be of central importance to understanding the relationship between deformation in the lithospheric mantle and crust. Existing analyses of obliquely convergent and divergent zones highlight the importance of kinematic boundary conditions and imply that stress may be of secondary importance in controlling the dynamics of deformation in the crust and lithosphere.

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“…In addition, attempts to relate regional lineation patterns to plate motions (e.g. Shackleton & Ries 1984;Ellis & Watkinson 1987) may also be unwise in transpression zones.…”

Section: Discussionmentioning

confidence: 99%

Transpression and transtension zones

1998

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“…Based on the model of thrust-and-wrench shearing parallel to a subduction zone, this orientation of the stretching lineation would correspond to a convergence angle of 45-55 • , depending on the dip of the subduction zone (curve 3 in Figs. 1 and 2 by Ellis and Watkinson, 1988). By contrast, the model of simple-inclined transpression (orthogonal shortening and strike-slip shearing with inclined walls) (Jones et al, 2004) suggests a more oblique convergence at an angle ≤ 20 • .…”

Section: Deformation Inside the Omzmentioning

confidence: 92%

“…Note, however, that the exhumation path has not resulted in a generalized L fabric, as it typically occurs under transtensional kinematics (e.g., Teyssier and Tikoff, 1999). For that reason, we use the double strikeslip and dip-slip shear model of Ellis and Watkinson (1988) in our estimates. According to this model and considering a shear zone dip of 45 • (Fig.…”

Section: Ductile Shearing At the Ciz-omz Boundarymentioning

confidence: 99%

“…According to this model and considering a shear zone dip of 45 • (Fig. 2, curve 3 in Ellis and Watkinson, 1988), the subhorizontal stretching lineation that characterizes the BCSZ would indicate a convergence/divergence angle of 15-35 • . We take 25 • for our calculations in Fig.…”

Section: Ductile Shearing At the Ciz-omz Boundarymentioning

confidence: 99%

“…Strain resulting from transpression is usually modeled as a combination of a three-dimensional coaxial component and an orthogonal simple shear component (Tikoff and Fossen, 1999). Less frequently, oblique convergence has been modeled as a combination of two simple shears, with lateral (wrenching) and orthogonal (thrusting) kinematics (Ellis and Watkinson, 1988). The oblique convergence/divergence that characterizes transpression usually involves deformation partitioning into thin bands concentrating lateral displacements and broader domains concentrating orthogonal displacements (e.g., Holdsworth and Strachan, 1991;Tikoff and Teyssier, 1994).…”

Section: Introductionmentioning

confidence: 99%

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Oblique collision and deformation partitioning in the SW Iberian Variscides

et al. 2016

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Abstract. Different transpressional scenarios have been proposed to relate kinematics and complex deformation patterns. We apply the most suitable of them to the Variscan orogeny in SW Iberia, which is characterized by a number of successive left-lateral transpressional structures developed in the Devonian to Carboniferous period. These structures resulted from the oblique convergence between three continental terranes (Central Iberian Zone, Ossa-Morena Zone and South Portuguese Zone), whose amalgamation gave way to both intense shearing at the suture-like contacts and transpressional deformation of the continental pieces in-between, thus showing strain partitioning in space and time. We have quantified the kinematics of the collisional convergence by using the available data on folding, shearing and faulting patterns, as well as tectonic fabrics and finite strain measurements. Given the uncertainties regarding the data and the boundary conditions modeled, our results must be considered as a semiquantitative approximation to the issue, though very significant from a regional point of view. The total collisional convergence surpasses 1000 km, most of them corresponding to left-lateral displacement parallel to terrane boundaries. The average vector of convergence is oriented E-W (present-day coordinates), thus reasserting the left-lateral oblique collision in SW Iberia, in contrast with the dextral component that prevailed elsewhere in the Variscan orogen. This particular kinematics of SW Iberia is understood in the context of an Avalonian plate salient currently represented by the South Portuguese Zone.

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Orogen‐parallel deformation of the Himalayan midcrust: Insights from structural and magnetic fabric analyses of the Greater Himalayan Sequence, Annapurna‐Dhaulagiri Himalaya, central Nepal

et al. 2016

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The metamorphic core of the Himalaya (Greater Himalayan Sequence, GHS), in the Annapurna‐Dhaulagiri region, central Nepal, recorded orogen‐parallel stretching during midcrustal evolution. Anisotropy of magnetic susceptibility and field‐based structural analyses suggest that midcrustal deformation of the amphibolite facies core of the GHS occurred under an oblate/suboblate strain regime with associated formation of low‐angle northward dipping foliation. Magnetic and mineral stretching lineations lying within this foliation from the top of the GHS record right‐lateral orogen‐parallel stretching. We propose that oblate strain within a midcrustal flow accommodated oblique convergence between India and the arcuate orogenic front without the need for strain partitioning in the upper crust. Oblate flattening may have also promoted orogen‐parallel melt migration and development of melt‐depleted regions between km3 scale leucogranite culminations at ~50–100 km intervals along orogen strike. Following the cessation of flow, continued oblique convergence led to upper crustal strain partitioning between orogen‐perpendicular convergence on thrust faults and orogen‐parallel extension on normal and strike‐slip faults. In the Annapurna‐Dhaulagiri Himalaya, orogen‐parallel stretching lineations are interpreted as a record of transition from midcrustal orogen‐perpendicular extrusion to upper crustal orogen‐parallel stretching. Our findings suggest that midcrustal flow and upper crustal extension could not be maintained simultaneously and support other studies from across the Himalaya, which propose an orogen‐wide transition from midcrustal orogen‐perpendicular extrusion to upper crustal orogen‐parallel extension during the mid‐Miocene. The 3‐D nature of oblate strain and orogen‐parallel stretching cannot be replicated by 2‐D numerical simulations of the Himalayan orogen.

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Orogen-parallel extension and oblique tectonics: The relation between stretching lineations and relative plate motions

Cited by 93 publications

References 0 publications

Transpression and transtension zones

Transpression and transtension zones

Oblique collision and deformation partitioning in the SW Iberian Variscides

Orogen‐parallel deformation of the Himalayan midcrust: Insights from structural and magnetic fabric analyses of the Greater Himalayan Sequence, Annapurna‐Dhaulagiri Himalaya, central Nepal

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