AEOLIAN DEPOSITION OVER ANTECEDENT LANDSCAPES: INSIGHTS FROM REGIONAL GPR IMAGING ALONG THE CURONIAN SPIT, LITHUANIA-RUSSIA

Capped by the highest coastal dunes in northern Europe, the Curonian Spit extends for 98 km along the southeast Baltic Sea and is divided between the Russian Federation to the south and the Republic of Lithuania to the north. Its curvature results in a gradual northerly (downdrift) change in exposure orientation from NW to W near the northern tip of the spit, with onshore westerly winds driving the aeolian transport since the early Holocene (>6 ka BP) formation of the proto-barrier. Over the past decade, several teams of collaborators have conducted digital SIR-2000 radar surveys using 200 MHz antenna to map the antecedent topography, thickness and extent of saturated and unsaturated dune strata, geometry and relative chronology of major bounding surfaces, as well as apparent dip angles and orientation of lateral migration surfaces (paleo-slipfaces). Remnants of massive dunes overlie a diverse suite of antecedent nearshore landscapes, lagoonal deposits, and older generations of aeolian strata. In addition to showing the sequence of accretion, subsurface images reveal superimposition and reactivation surfaces indicative of distinct activity phases associated with regional climatic deterioration, wildfires, and recent deforestation. A number of regionally correlated bounding surfaces and paleosols formed the framework for establishing an integrated optical luminescence and radiocarbon-based chronology along parts of the northern section of the spit. GPR images and occasional surface exposures of aeolian strata show evolution in dune morphologies (e.g., barchan and parabolic to transverse) and allow reconstruction of compound dune heights (>40 m) and volumes. Along the entire length of the Curonian Spit, more than 700 million m³ of sand have undergone several phases of regional migration and stabilization, with the last pulse of activity corresponding to the Little Ice Age. Much of the recent (AD 1700-1900) history of the spit has been punctuated by sand invasion into forests and leeward settlements, resulting in repeated southward relocations. Regional geological studies complemented with high-resolution (>400 MHz) local surveys are aimed at site-specific paleogeoraphic reconstructions, correlation of near-surface anomalies with diagnostic GPR reflections, and assessment of cultural heritage.