Fringed Patagonian tableland: One of Earth's largest and oldest landslide terrains

Abstract

Sedimentary and volcanic tablelands host the world's largest landslide areas, sometimes spanning hundreds of kilometers along escarpments. This study, employing new remote sensing-based mapping and drawing on an expanding body of literature on paleogeographic evolution, revises the extent, controls, and chronology of some of Earth's largest coalescent landslides in the volcanic tableland of extra-Andean Patagonia. Mostly ancient rotational slides and rock spreads, accompanied by earthflows and occasional rock avalanches, cover approximately 30,000 km², roughly a fifth of the Patagonian escarpments, with the largest landslide areas exceeding 1000 km². The immense size of the failed tableland in Patagonia is inherited from stratigraphy and geological history: weak marine and continental Cretaceous-Miocene sedimentary and volcaniclastic rocks, capped by plateau basalts, create a highly unstable environment, outcropping along thousands of kilometers of escarpments. Most landslide areas occupy the steepest, most dissected parts of Patagonian tableland, occurring independently of recent climatic conditions. Some of the largest complexes are found in both the most humid and arid regions. Cross-cutting relationships between landslides and dated glacial, lacustrine, marine deposits, and lava flows reveal that some landslides have persisted for several million years, marking them as some of Earth's oldest landslide terrains with distinctive geomorphological footprints. Future research on failed Patagonian tableland should include direct radiometric dating, InSAR technology monitoring, and numerical stability modeling of landslides. This comprehensive approach will deepen our understanding of their origins and determine whether these giant landslide fringes predominantly represent fossil features or could be reactivated under contemporary environmental conditions.