Plate corners where convergence transitions to strike-slip motion, as on the southern Alaskan margin 18, 32, 33, 34, require a more specific model configuration that includes asymmetric structural features linked with the lateral change from subduction/collision to transform tectonics. Such generic model setups may only be applicable to plate boundaries with moderate and/or symmetric slab curvature, such as the South American 28, 29 or Cascadia 30, 31 subduction zones. The coupled thermo-mechanical/landscape evolution modelling 17, 24 has reconciled these end-member views on deep and fast exhumation at plate corners showing that the highest rock uplift rates are concentrated in areas where a large erosion potential spatially coincides with strong tectonic forces.ĭespite progress in numerical modelling of orogen syntaxes, previous studies were limited to a symmetrical indenter bulge 15, 16, 17, 24 introduced to mimic slab bending at plate corners 25, 26, 27.
A prominent counter-argument to the “tectonic aneurysm” hypothesis emphasizes the crucial role of the geometry of the subducting slab at plate corners for initiating localized deformation and exhumation in orogens 15. This surface uplift further intensifies erosional processes and exhumation. Spatially localized lithospheric deformation and focused rapid rock uplift (> 5 mm yr −1), which is commonly detected at orogen syntaxes 18, 19, 20, have long attracted the attention of geoscientists.Īccording to the “tectonic aneurysm” hypothesis 21, 22, 23, rapid exhumation of rocks is promoted by vigorous fluvial or glacial incision that erodes the cold and strong uppermost crust, thus leading to temperature-dependent crustal weakening and increased surface uplift. Deformation partitioning in such kinematic transition zones exhibits considerable spatial and temporal variations depending on plate geometry 15, rheological properties of the overriding plate 16, and intensity of surface erosion 17. Plate corners are curved segments of convergent plate boundaries and give rise to diverse and complex tectonic and geomorphic processes. Recent technical and conceptual advances in thermo-mechanical 1, 2, 3, 4, 5, 6 and landscape evolution 7, 8, 9, 10 numerical modelling have expanded the ability to investigate the combined effects of geodynamic processes and geomorphic conditions 11, 12, 13, 14 in different tectonic settings including plate corners. From these results, we suggest that the general exhumation patterns observed in southern Alaska are controlled by mutually reinforcing effects of tectonic deformation and surface erosion processes. The focused exhumation of the Chugach Core also finds its equivalent in model predicted zones of high rock uplift rates in an isolated region above the indenter. In particular, relatively young thermochronological ages are reproduced along the plate-bounding (Fairweather) transform fault and in the area of its transition to convergence (the St. The resulting first-order deformation/rock uplift patterns show strong similarities with observations. Here, we present the results of fully-coupled thermo-mechanical (geodynamic) and geomorphologic numerical modelling, the design of which captures the key features of the studied area: subduction of oceanic lithosphere (Pacific plate) is adjacent to a pronounced asymmetric indenter dipping at a shallow angle (Yakutat microplate), which in turn is bounded to the east by a dextral strike-slip shear zone (Fairweather fault). The southern Alaskan margin with its curved convergent plate boundary and associated zones of localized uplift is a prime location to study active orogeny. Plate corners with extreme exhumation rates are important because they offer a perspective for understanding the interactions between tectonics and surface processes.
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