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

Karla Rubio-Sandoval, Timothy Shaw, Matteo Vacchi, Nicole S Khan, Benjamin P. Horton, Rodolfo José Angulo, Marta Pappalardo, Augusto L. Ferreira, Sebastian Richiano, Maria Cristina De Souza, Paulo Cesar Fonseca Giannini, Deirdre D. Ryan, Evan J. Gowan, Alessio Rovere 

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.