Paraglacial mega-barriers of the Baltic Sea: a decade of collaborative research

In contrast to tidally influenced coastlines of many paraglacial regions (New England, Alaska, northern Europe, Siberian Arctic), the southeast Baltic Sea coast experiences only cm-scale tidal effects. As a result, storm wave-generated, and especially aeolian processes, act as the dominant driving forces in coastal morphodynamics. North of Sambian Peninsula, a 100-km-long Curonian Spit (Russia and Lithuania) transitions northward into a mainland coast of northern Lithuania and Latvia, culminating in a massive prograded strandplain along an isostatically stable segment at Cape Kolka. During the past decade, high-resolution geophysical surveys (100-500 MHz GPR) and sedimentological datasets, complemented by radiocarbon and optical dates, have enhanced our understanding of dunescape evolution and chronology of aeolian activity along this part of the Baltic coast. Due to Curonian Spit width and height (15-60 m), dune aggradation and landward migration (rather than breaching and overwash) contribute to barrier retrogradation. Georadar images of Mid-Holocene and recent megadunes reveal a diverse suite of paleo-slipface sequences, with prominent radar reflections corresponding to paleosols and horizons enriched in heavy minerals. The latter not only aid local stratigraphic correlation, but serve as paleo-wind indicators. Heightened storminess (correlated with several NAO anomalies), regional forest fires, and widespread land clearing since medieval times, resulted in major landscape reorganization through parabolic-to-transverse transformation and sand inundation of antecedent landscapes. Renewed interest of Cape Kolka strandplain focuses on both the postglacial paleoshorelines and the mechnaisms of formation of high (5-10 m) compound beach/dune ridges during the Holocene. Ultimately, this research effort will be integrated with investigations along the shoreline of Poland to the south, which experiences a relative sea-level rise and to the north, where glacioistostatic rebound still influences the evolution of the Estonian coastline.