Slab flattening and the rise of the Eastern Cordillera, Colombia

摘要

The topographic growth of a mountain belt is commonly attributed to isostatic balance in response to crustal and lithospheric thickening. However, deeper mantle processes may also influence the topography of the Earth. Here, we discuss the role of these processes in the Eastern Cordillera (EC) of Colombia. The EC is an active, double-vergent fold and thrust belt that formed during the Cenozoic by the inversion of a Mesozoic rift, and topography there has risen up to similar to 5,000 m (Cocuy Sierra). The belt is located similar to 500 km away from the trench where two separate portions of the Nazca plate subduct below the South American plate. North of 5 degrees N, the EC rises above a flat-slab subduction region. Volcanic arc migration implies slab shallowing by similar to 10 Ma and flattening up to the present-day configuration at similar to 6 Ma. The occurrence of a high v(p)/V-S anomaly and clustered seismicity below the belt at similar to 160 km depth delineates the slab geometry and has been related to dehydration of the slab, suggesting the presence of a hydrated mantle wedge.