| Schreurs, G. and Colletta, B. 2002. Analogue modelling of continental transpression. Schellart, W. P. and Passchier, C. 2002. Analogue modelling of large-scale tectonic processes. Journal of the Virtual Explorer, 7, 67-78. | ||
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Analogue
modelling of continental transpression
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G. Schreurs1 & B. Colletta2 1Institute
of Geological Sciences, University of Bern, Baltzerstrasse 1, CH-3012
Bern, Switzerland
Abstract Experiments were performed to simulate deformation in zones of continental transpression. Stratified models consisted of brittle analogue materials overlying a thin layer of viscous material. Transpression was obtained by combining basal, distributed strike-slip shear with transverse shortening. Analysis of our models by X-ray computerized tomography allowed a detailed analysis of their internal geometry and kinematics. On the basis of X-ray CT images, short movies were generated using computer visualisation software. The applied ratio of shear strain rate and shortening strain rate exerts an important control on initial fault evolution. In those experiments with a relatively high strain rate ratio (>3.6), sub-vertical, en echelon strike-slip faults formed first, striking at angles of 25°-37° to the shear direction. During increasing deformation, several convergent strike-slip fault zones formed displaying positive flower structures. In contrast, failure of brittle layers in low strain rate ratio (<2.7) experiments was accommodated by gently dipping (30-45°), downward converging thrust faults that bound pop-up structures and strike parallel to the shear direction. Although initially transpression is taken up either by pure strike-slip faults or by pure reverse faults, increasing deformation results in a fault pattern dominated by oblique-slip faults. Partial partitioning of fault motion occurred at late stages of transpression when strike-slip faults formed within pop-up structures. These strike-slip faults merge at depth with confining oblique-slip reverse faults, have a curved fault trace in plan view and a dip direction which changes along strike. Fault patterns can be used as kinematic indicators to determine whether transpression has a sinistral or dextral shear component. The detailed 3D imaging of our experiments might provide constraints for geometric and kinematic interpretations of complex structures in zones of continental transpression.
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