Geomorphology of coastal formations on present and ancient sandy coasts

Many coastal sites are experiencing land uplift, so coastal formations can be found many kilometres inland from the present day shoreline. However, due to the relatively rapid, site specific and complicated development, their evolution is not very thoroughly studied yet. In this study, we analyse sediments and subsurface stratigraphy to explain the evolution and geomorphology of coastal formations (from present to ancient coastlines) located in sediment supply-limited areas. Several study sites were chosen on Tahkuna Peninsula, Hiiumaa Island in Estonia, where the rate of land uplift is 2.8 mm yr−1. Due to deficiency of sediment, dunes and old beach ridges that developed during the last 3,500 years are low (dunes up to 6–7 m, the studied ridges mostly less than 2 m). The coastal formations studied are located at different distances (up to 1 km) from the shoreline and at different altitudes (up to 13.2 m above sea level).

In the current research, granulometric analysis was used for studying the coastal formations; grain size was determined by dry sieving of sediments. Additional studies were carried out with ground-penetrating radar (SIR-3000) to compare the present and former coastlines and to explain geomorphic differences. Drilling was also used and special pits were dug for the examination of mineral deposits. The preliminary results show that the sands on the present coastline are similar to those of former shorelines, which may be caused by the wind regime, time scale for coastal formation development, and underlying sediments.