Morphological dating of fluvial terraces using high resolution GNSS profiles and satellite derived DEMs with application to Patagonia, Argentina

Changing climatic conditions cause alluvial rivers to aggrade and incise, which can result in the formation of multi-generational fluvial terrace sequences. Such records can be used to investigate past interactions between climatic conditions and the fluvial system and to predict channel responses to future climatic change. To accurately assess such interactions, precise dating of terrace sequences is vital. However, established methods such as ¹⁰Be exposure dating are costly and time intensive. Thus, they are impractical for application to spatially extensive areas and for establishing patterns of along-stream aggradation or incision.

An alternative approach of dating fluvial terraces is based on the degradation of the slope (riser) between successive terraces by down-slope sediment transport. Here we present a tool for analyzing high-resolution elevation profiles across alluvial terrace risers and inferring their age since abandonment, based on linear and nonlinear hillslope diffusion models. We extend this workflow to the analysis of DEM-derived riser profiles that can provide a greater spatial extent and resolution than GNSS profiles or exposure ages. A set of ¹⁰Be exposure ages dating back to ca. 1 Myr from terraces around the Río Santa Cruz, Patagonia is used for calibration and to test the method’s viability. Preliminary results highlight the importance of post-abandonment riser disturbances and variability in hillslope sediment-transport rates.

This technique provides a low-cost, spatially extendable way of dating fluvial terraces and analyzing landscape dynamics in fluvial systems. We are currently preparing to release an open-source Python package for performing these analyses.