Higher than present global mean sea level recorded by an Early Pliocene intertidal unit in Patagonia (Argentina)

Reconstructions of global mean sea level (GMSL) from past warm periods can help constrain future projections of sea level rise. This study analyzes a geological unit in central Patagonia, Argentina, dated to the Early Pliocene (4.69–5.23 Ma) using strontium isotope stratigraphy. Interpreted as an intertidal environment, the unit's elevation is approximately 36 m above present-day sea level. After accounting for glacial isostatic adjustment and vertical land movement, the study estimates that GMSL during deposition was 28.4 ± 11.7 m above present. This aligns with similar Early Pliocene sea level proxies from the Mediterranean Sea and South Africa, suggesting Early Pliocene GMSL may have exceeded 20 m above present levels. Such high GMSL values imply an ice-free Greenland, significant West Antarctic melting, and a contribution from East Antarctic marine-based sectors.

Alessio Rovere, Marta Pappalardo, Sebastian Richiano, Marina Aguirre, Michael R. Sandstrom, Paul J. Hearty, Jacqueline Austermann, Ignacio Castellanos, Maureen E. Raymo