Molecular to macrofossils indicating last millennium sea level in Lavsa saltpans, Croatia

Intertidal salt production sites existed continuously around the Mediterranean since classical antiquity, and their remains are present in large numbers along the Dalmatian (east Adriatic) coast. Most of them are preserved and dated to medieval times. This study aims to develop complementary proxies identifying the salt production layer in submerged ancient saltpans of Lavsa, a remote island on the central Dalmatian coast, to date the saltwork units by optically stimulated luminescence (OSL) and use them to infer changes in sea level. The significance of the study is in the application of molecular fossil analyses identifying the hypersaline layer in the sediments from a core drilled in the saltpan's site. The molecular fossil analyses correlate with the results of micro and macrofossil analyses and geochemical findings, all representing the saltwork unit. The depth of the hypersaline layers and the OSL dates provide relative sea level (RSL) lower limiting points of −145 ± 5 cm at 1309 ± 33 CE, probably the time when salt production started in Lavsa, and −115 ± 5 cm at 1364 ± 52 CE when saltwork activities ended. These limiting points extend the known RSL index point in Lavsa Island of −92 ± 8 cm, with an updated average age of 1337 ± 62 CE, correlating with the historical records. Medieval lower sea levels were also observed in the northern and southern parts of the east Adriatic coast as well as in other parts of the Mediterranean, probably driven by climate-related events, generating centennial-scale fluctuations in past sea levels that cannot be predicted by glacial isostatic adjustment (GIA) models.