9. Late Glacial to Holocene Environmental Changes (with Particular Reference to Salinity) in the Southern Baltic Reconstructed from Shallow Water Lagoon Sediments

Palaeoenvironmental reconstructions can provide important information into the processes influencing the long-term development of the Baltic Sea since the Last Glacial Maximum. This paper uses lithological and diatomological evidence from two sediment cores to reconstruct the palaeoenvironments of the mouth of the Rega Valley, Poland. We use the ecological preferences of diatoms to qualitatively reconstruct changes in salinity over the same period. Results between the two cores correspond, and demonstrate that both basins have experienced a series of marine transgressions, coastal aggradation, and lagoon development over the Late Glacial and Holocene. Surprisingly, our high-resolution core profiles demonstrate that conditions varied between fresh brackish and brackish fresh for most of the Holocene (Boreal through Subatlantic Chronozones), whilst the well-documented mid-Holocene peak in salinities between 6.000 and 5.000 cal. BP was not observed in our records. It is likely that this indicates the buffering of the Baltic waters from freshwaters from the south, and demonstrates the importance of terrestrial-hydrological processes for determining the long-term stability of the salinities in the southern Baltic coastal zone.