ubcrustal loads in the andean foreland and pampean plain: stratigraphic, topographic and geophysical evidence

Abstract

In the Central Andes, supracrustal tectonic loading has been extensively invoked to explain retroarc flexure and foreland basin subsidence, due to stacking of tectonic slivers and amplification by sedimentary loads. However, we present surface and subsurface stratigraphic data from the Sierras Pampeanas broken foreland that suggest a long-wavelength subsidence pattern (>500 km), which is difficult to explain with upper crustal loads that are generally associated with short wavelength (< 300 km) subsidence. It is proposed that stratigraphic, structural, topographic and geophysical features in the Sierras Pampeanas region and Chaco-Paranense basin can be explained by flections driven by processes occurring in the asthenosphere and/or lower crust, like thermal-driven corner mantle flow and/or eclogitization, respectively. Short-wavelength flexure (<300 km) driven by various factors enhances regional subsidence features.