Publication Date:
2010-03-21
Description:
Cordilleran-type orogens are characterized by the formation of mountain chains and ridges near subduction zones. The growth of orogenic systems is sustained by frictional and viscous stresses, which promote surface uplift. However, horizontal extensional stresses also develop, which can contribute to the formation of marginal basins and gravitational orogenic collapse. Here we use a numerical model to assess the effects of the buoyancy of the mantle wedge overlying the subduction zone on the evolution of Cordilleran orogenic systems. Our simulations show that as the subduction velocity decreases, stresses from the buoyancy of the mantle wedge can drive trench retreat and the formation of marginal basins. We find that ultimately, these stresses promote the gravitational collapse of the orogen, detachment of microplates and the break-up of active plate margins. We suggest that the effects of mantle-wedge buoyancy could explain the collapse of the East Gondwana Cordillera, constructed along the edge of the Australia/East Antarctic craton as the Gondwana and Pacific-Phoenix plates converged. We propose that 105-90million years (Myr) ago, a change in the absolute plate motion reduced the subduction velocity, ultimately triggering the gravitational collapse of the orogen and the fragmentation of the active margin. © 2010 Macmillan Publishers Limited. All rights reserved.
Print ISSN:
1752-0894
Electronic ISSN:
1752-0908
Topics:
Geosciences
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