Yoldia Sea

The Yoldia Sea is the brackish-to-marine stage of the Baltic basin in the early Holocene, roughly 11,700 to 10,700 years before present, named for the cold-water bivalve Portlandia, formerly Yoldia, arctica found in its sediments. It followed the freshwater Baltic Ice Lake, which drained about 25 m as the retreating Scandinavian ice sheet opened a connection across south-central Sweden to the ocean. That connection let intermittent saltwater enter, though much of the stage stayed nearly fresh. Ongoing glacial isostatic uplift then closed the outlet, giving the freshwater Ancylus Lake. Yoldia sediments and shorelines are key markers in Baltic relative sea-level and deglaciation reconstructions.