Dynamic topography in the Argentine Pampas

DÁVILA, F.M., LITHGOW-BERTELLONI, C.

Londres

Conferencia; Dynamic Topography, A Key Surface Record of Deep Earth Processes; 2011

The Geological Society

The Argentine Pampean foreland or Pampas, located at leading edge of the modern flat slab of the south-central Andes between 31º-33º SL (Plain in Fig. 1), is examined in order to understand the large-scale topography using flexural and gravity studies together with computations of dynamic topography. At scales 400 m (Fig. 1) and with depocenters >400 km eastward with respect to flexural models (Fig. 3). The discrepancy suggests that two mechanisms, acting at different wavelengths, influenced in the formation of the Argentine Pampas. The basin preservation, generated since the arrival of the flat subduction to this segment of the Andes, is likely the result of large-scale geodynamic forcing. Models of mantle flow, driven by realistic flat-slab subduction geometry and density contrasts, reproduce the depocenter location and the wavelength of subsidence as well as most of the remaining amplitude. Nonetheless, more sophisticated studies (e.g. considering lateral viscosity variations in the mantle wedge) might help reduce the dynamic amplitudes and better reproduce the observed geological record.