Fluvial responses to Holocene climatically induced coastline migration in the Iguape River estuary (Southeast Brazil)

Rivers represent intricate geomorphological systems that exhibit sensitivity to even subtle base-level changes. This study examines the geomorphological response of Ribeira de Iguape River, located along the southern coast of São Paulo state, Brazil, to hydrological changes and coastline migration resulting from Holocene climate pulses. Using a multidisciplinary approach, including geomorphological and stratigraphical analyses, optically stimulated luminescence dating, grain-size analyses, interpretation of satellite images, mapping and reassessment of previous studies, we investigated the potential impacts of these geomorphological dynamics on the river system. Our study reveals two distinct orders of low fluvial terraces, typically inserted no more than 10 m above the average channel discharge, which are geochronologically correlated with the low marine terraces that document the former coastline position at the river mouth, as previously identified in other studies. Such findings indicate a deposition phase when the coastline was stabilised on the inner continent in the Medieval Warm Period, as well as an erosion phase when the coastline migrated seaward during the Little Ice Age. This research contributes to improving our understanding of how rivers can respond to base-level changes and provides valuable insights into the dynamic interactions between river systems and coastal environments.