Holocene relative sea-level changes from the Atlantic coasts of South America

Holocene relative sea-level (RSL) changes along the Atlantic coast of South America reflect a complex interplay between ice equivalent sea-level, glacio-isostatic adjustment (GIA), regional tectonics, and local sedimentary processes. However, the uneven spatial and temporal resolution of existing Holocene RSL data has hindered regional assessments. Here, we compile and standardize 1108 RSL data points from Brazil, Uruguay, Argentina, and Chilean Tierra del Fuego, creating the first comprehensive database for the southwestern Atlantic. The data reveals a widespread Mid-Holocene highstand between 7000 and 4000 years BP, with RSL rising 2 to 4 m above present-day sea level, followed by a gradual fall to present. This pattern is consistent with GIA model predictions across the region's > 50° latitudinal span. Peak rates of RSL change occurred during the Early to Mid-Holocene transition, reaching up to 17.2 mm/yr in Tierra del Fuego and decreasing to 1.6 mm/yr near the Amazon delta. After 5000 years cal BP, RSL started to fall at 0.5 mm/yr. This Atlantic coast of South America database fills a critical geographic gap and provides a robust framework for refining GIA models and understanding sea-level evolution during the Holocene in the Southern Hemisphere.