Impact of indentor geometry on lithosphere deformation - insights from analogue vice models
Abstract
Vice models incorporate a weak lithospheric unit that is compressed between two stronger blocks (vices) analogous to settings with thickened or juvenile crust and high surface heat flow surrounded by colder and stronger continental lithosphere (e.g. plateau orogens). We report the results of laboratory vice models that examine the effect of the geometry of bounding indentor blocks (curvature, size, symmetry) on deformation within the intervening weak orogen. We also analyse the influence of the indentor geometry in combination with different degrees of buoyancy (buoyant and non-buoyant) of the weak lower crust. The upper crust of both the vice blocks and the weak orogen consists of sand; the ductile lower crust and mantle lithosphere layers are composed of mixtures of silicone polymers and plasticene. The model lithosphere floats isostatically on an asthenosphere of water. Surface deformation in the experiments is monitored by a digital stereoscopic camera system and particle imaging velocimetry. This allows high spatial and temporal resolution of the strain evolution in the upper crust, the development of topographic relief, and velocity fields (analogue to GPS data). After each experimental run, the sand cover of the upper crust is removed to examine lower crustal structures. Cross sections cut perpendicular to the orogen record the finite deformation of the lower crust and the mantle lithosphere. The structural inventory developed in the experiments includes thrust faults of variable vergence and reverse faults bounding pop-up structures within the upper crust; and cusp-shape folds bounding deep synclines within the lower crust. The plate geometry is reflected in the initial outline of topography, but the overall geometry of the fault pattern does not show any recurrent shape of the vice blocks. We conclude that plate or indentor geometry does not have a first order, but only a second order influence on structural evolution in the models, as different vice geometries still result in distinct patterns.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.T23B0496S
- Keywords:
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- 8108 Continental tectonics: compressional;
- 8120 Dynamics of lithosphere and mantle: general (1213);
- 8159 Rheology: crust and lithosphere (8031);
- 8175 Tectonics and landscape evolution;
- 8194 Instruments and techniques