Vilumaa, K., Tõnisson, H., Kont, A. and Ratas, U., 2013 Ground-penetrating radar studies along the coast of Estonia.

Ground-penetrating radar (GPR) profiling has been performed in the study sites in west Estonian archipelago (Röögu, Lõimastu) and on the northern coast of the mainland (Juminda). The west Estonian study sites have emerged during regressive phases of the Limnea Sea. The coastal landforms there are younger and smaller than the landforms in northern Estonia, which have emerged at the beginning of the Ancylus Lake stage of the Baltic Sea. The study sites are characterized by a series of beach ridges, which are parallel to the shoreline. These ridges are separated by narrow and wet depressions where non-calcareous sand is covered with peat. The beach ridges are located at different distance from the current shore and at different altitudes. The results are based on cartographic analysis, topographic survey and georadar (SIR-3000, 100 MHz frequency) survey along transects. About 1 km long GPR profiles perpendicular to the ridges were examined. The GPR data were calibrated and compared with peat coring data. The average electromagnetic wave (EMW) speed values were: 0.035 m/ns for peat and 0.05 m/ns for sand. The study was conducted in order to determine the thickness of peat (0.2–2.0 m) and to characterize the topography of sub-peat mineral surface. Two different patterns of bedding in the sand layer can be detected. The top layers (1–1.5 m), which are probably of aeolian origin, are almost parallel to the surface of the initial beach ridges. Most of the lower layers are tilted seaward. Those layers may indicate a cross-shore transport of sand by waves.