Basin dynamics in the Pampas Plain, Argentina

DAVILA, F.M. Y LITHGOW-BERTELLONI

Congreso; EGU General Assembly; 2012

The Argentine Pampean foreland or Pampas Plain, located at leading edge of the modern flat slab of the southcentral Andes between 31º-33º SL, is examined in order to understand the large-scale subsidence using flexural and gravity studies together with computations of dynamic topography. At scales 400 km eastward with respect to flexural models. The discrepancy suggests that two mechanisms, acting at different wavelengths, might have influenced in the formation of the Argentine Pampas. The basin preservation, generated by the subduction dynamics of this segment of the Andes, is likely the result of large-scale dragging forces. Models of mantle flow, driven by realistic subducting slab geometries and density contrasts, reproduced the depocenter location and the wavelength of subsidence as well as most of the remaining amplitude. However, while the net dynamic subsidence across the Pampas was 200-100 m during the early Miocene normal-dipping subduction stage of the Andes, the Pliocene to Holocene slab flattening, in contrast to expected, reproduced very small negative dynamic topography values (