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

Holocene sea-level changes along the Atlantic coast of South America reflect a complex interplay between glacio-isostatic adjustment (GIA), regional tectonics, and local sedimentary processes. However, the uneven spatial and temporal resolution of existing sea-level data has hindered regional-scale assessments. Here, we compile and standardize 1108 relative sea-level (RSL) data points from Brazil, Uruguay, Argentina, and Chilean Tierra del Fuego, creating the first comprehensive Holocene RSL database for the southwestern Atlantic. The data reveal a widespread Mid-Holocene highstand between ~7000 and 4000 cal BP, with sea level rising 2 to 4 m above present, followed by a gradual fall to modern levels. 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 cal BP, RSL rates decelerated, averaging –0.5 mm/yr into the Late Holocene. This standardized database fills a critical geographic gap and provides a robust framework for refining GIA models and understanding sea-level evolution since the Last Glacial Maximum in the Southern Hemisphere.