Subfossil mollusc shells of the Baltic Sea and the possibilities of their usage in the stratigraphy and correlation of the Baltic Sea sediments

Subfossil mollusc shells in Estonia are widely spread both in contemporary and ancient sediments and for a long time they have served successfully for stratigraphical, palaeogeographical and archaeological purposes. There are extremely good conditions for the investigation of the subfossil mollusc fauna in Estonia. The bedrock in coastal area consists here mainly of limestones and dolomites, which are covered with carbonaceous till and aqueoglacial deposits. In Estonian nearshore environs molluscs had suitable living conditions and enough material to build up the shells. They are better preserved than in neighbouring countries. The molluscs can give precise information about the conditions of palaeobasins. This is primarily due to their good preservation and a large number of species. Their history began in the Palaeozoic Era and they are spread nearly in all biotopes. The molluscs are rather susceptible to the environment they inhabit and can therefore give information about the water depth, salinity, temperature and isotopic composition of water. Malacological method will give a great help in the correlation of the on- and offshore deposits and landforms and this method is well developed in Estonia