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Volume 9, issue 6 | Copyright
Solid Earth, 9, 1207-1224, 2018
https://doi.org/10.5194/se-9-1207-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 05 Nov 2018

Research article | 05 Nov 2018

The influence of upper-plate advance and erosion on overriding plate deformation in orogen syntaxes

Matthias Nettesheim1, Todd A. Ehlers1, David M. Whipp2, and Alexander Koptev1 Matthias Nettesheim et al.
  • 1Department of Geology, University of Tübingen, Tübingen, Germany
  • 2Department of Geosciences and Geography, University of Helsinki, Helsinki, Finland

Abstract. Focused, rapid exhumation of rocks is observed at some orogen syntaxes, but the driving mechanisms remain poorly understood and contested. In this study, we use a fully coupled thermomechanical numerical model to investigate the effect of upper-plate advance and different erosion scenarios on overriding plate deformation. The subducting slab in the model is curved in 3-D, analogous to the indenter geometry observed in seismic studies. We find that the amount of upper-plate advance toward the trench dramatically changes the orientation of major shear zones in the upper plate and the location of rock uplift. Shear along the subduction interface facilitates the formation of a basal detachment situated above the indenter, causing localized rock uplift there. We conclude that the change in orientation and dip angle set by the indenter geometry creates a region of localized uplift as long as subduction of the down-going plate is active. Switching from flat (total) erosion to more realistic fluvial erosion using a landscape evolution model leads to variations in rock uplift at the scale of large catchments. In this case, deepest exhumation again occurs above the indenter apex, but tectonic uplift is modulated on even smaller scales by lithostatic pressure from the overburden of the growing orogen. Highest rock uplift can occur when a strong tectonic uplift field spatially coincides with large erosion potential. This implies that both the geometry of the subducting plate and the geomorphic and climatic conditions are important for the creation of focused, rapid exhumation.

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In this modeling study, we investigate rock uplift at plate corners (syntaxes). These are characterized by a unique bent geometry at subduction zones and exhibit some of the world's highest rock uplift rates. We find that the style of deformation changes above the plate's bent section and that active subduction is necessary to generate an isolated region of rapid uplift. Strong erosion there localizes uplift on even smaller scales, suggesting both tectonic and surface processes are important.
In this modeling study, we investigate rock uplift at plate corners (syntaxes). These are...
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