Accumulation of heavy minerals in the eastern coast of the Gulf of Riga, south-western Estonia

The Baltic Sea is characterised by tectonic conditions that cause its northern parts to lift and southern parts to sink. Our study area (eastern coast of the Gulf of Riga) has been rather stable for a long time. During transgressive phases in the course of the sea's invasion to the coast intensive mechanical and mineralogical differentiation of the sediments took place, causing the separation of heavy minerals. The largest concentrations of heavy minerals were found in transgressive sediments of the Litorina Sea. Their concentration was especially high in the Lemmeoja site (in some layers up to 83.7% of the sediment). The goal of our research was to study the heavy mineral content and composition in different age sediments of the area and to find regularities in the accumulation processes through time. To achieve our aim we collected samples from 16 sites between Parnu and Ikla in south-western Estonia. The heavy mineral content in the whole investigated area is high, amounting on average to about 5%. The deposits of transgressive phases of the Baltic Sea are more reworked than those of the regressive phases and contain more heavy minerals. Our investigation of initial rocks allows to conclude that garnets and zircon originated mainly from the Devonian sandstones of the Arukula and Narva regional stages, amphiboles and pyroxenes mainly from Quaternary deposits.