Grudzinska, I., Saarse, L., Vassiljev, J., Heinsalu, A.
Biostratigraphy, shoreline changes and origin of the Limnea
Sea lagoons in northern Estonia: a case study of Lake Harku
The paper presents diatom, loss-on-ignition, magnetic
susceptibility, and radiocarbon data to reconstruct the depositional history
and evolution of Lake Harku, a former Limnea Sea lagoon. Harku is one of the
youngest isolated lakes that has been studied bio- and chronostratigraphically
in Estonia to date. Based on changes in diatom assemblages, four evolutionary
stages in basin development have been recognized (lagoon, semi-enclosed lagoon,
transitional and closed lake). Shoreline positions at 2000, 1500, 1000 and 800
cal BP have been reconstructed and displayed on 3D palaeogeographic maps. Lake
Harku became isolated from the Limnea Sea at ~800 cal BP, followed by
occasional seawater incursions over the next 300 years. Plain landscape,
low-lying sill threshold, and proximity to the sea contributed to extended
basin isolation.