Abstract

The tectonically active South American margin is characterized by the accumulation of deformation contributing to uplift of the Andean forearc at millennial time scales. However, the mechanisms responsible for permanent coastal uplift are debated, mainly because methodologically consistent, continental-scale analyses of uplifted terraces have not yet been carried out for South America. Uplifted marine terraces are generally used to infer permanent coastal deformation and uplift; we used almost 2,000 measurements of last-interglacial marine terraces to calculate an uplift-rate signal on which we performed a wavelength analysis. The same spectral analysis was applied to tectonic and subduction parameters associated with accumulation of permanent deformation to detect possible links with the uplift-rate signal. The uplift-rate signal displays a constant background-uplift rate along the margin, perturbed by changes at variable wavelengths. Similarities between its wavelength spectrum and the spectra of tectonic parameters suggest potential correlations pointing toward underlying processes. For example, crustal faulting is mainly responsible for short-wavelength deformation; intermediate-wavelength to long-wavelength tectonic features indicate various extents of locked areas on the megathrust that relate to its long-term seismotectonic segmentation. We suggest that moderate, long-term background uplift is caused by major, deep earthquakes near the Moho, although records of such events are sparse. Due to their disparate occurrence, we infer accumulation of permanent deformation over millennial time scales through multiple, distinct uplift phases that are spatially and temporally distributed. Our study highlights the application and utility of a signal-analysis approach to elucidate the mechanisms driving surface deformation in subduction zones at a continental scale.