Albertas Bitinas

Aeolian Sand Invasion: Georadar Signatures from the Curonian Spit Dunes, Lithuania

Aeolian landforms may occupy large portions of coastal spits and often consist of multiple generations defined by periods of stability and reactivation. Where earlier phases of aeolian activity are masked by subsequent deposition, continuous high-resolution (200 MHz) ground-penetrating radar (GPR) images are used to reconstruct their dynamic history. Subsurface profiles from younger segments of the Great Dune Ridge massif along the northern Curonian Spit, Lithuania reveal several phases of dune migration, which generally correspond to climatic deterioration during the Little Ice Age. Exacerbated by regional deforestation, 15–30-m-high dunes have invaded coastal settlements, causing their repeated relocation. Along the study transect, an optical age of the younger slipface strata is consistent with the record of village entombment by drifting sand by AD 1797. This study demonstrates that in the absence of mappable paleosols, a combination of geophysical, luminescence-dating, and documentary databases offers a means of reconstructing the history of human-landscape interaction, with potential implications for the future stewardship of natural and cultural resources along spit coastlines.

Unique Baltic Outcrops Reveal Millennia of Ecological Changes

Throughout Earths history, tectonic forces, often violent and unpredictable, have been responsible for exposing geological formations to scientific scrutiny. But forces of uplift are not restricted to plate boundaries. For example, when looking at forested coastal dunes bordering placid Curonian Lagoon along the Lithuanian coast of the Baltic Sea, one hardly suspects that any powerful forces are at work. Yet this is a site where massive migrating hills of sand have put pressure on the deep strata of the ancient lagoon, forcing its sediments to the surface and offering rare access to fossils of the Holocene, which spans the past 10,000 years.

Geological Structure of the Quaternary Sedimentary Sequence in the Klaipėda Strait, Southeastern Baltic

The Klaipėda Strait is located between the Curonian Spit and the mainland coast of Lithuania. It links the Curonian Lagoon with the Baltic Sea. The Quaternary sequence is represented here by Pleistocene sediments formed during a few glaciations and interglacials. Its uppermost part is composed of Late glacial and Holocene sediments originating from different stages of the Baltic Sea development. One of the main problems of Quaternary geology in the vicinities of the Klaipėda Strait, as well as in the whole Lithuanian Coastal Area, is the reliable geochronology and stratigraphic correlation of sediments. To contribute to the solution of this problem, the infrared optically stimulated luminescence (IR-OSL) dating of the lacustrine inter-till sandy sediments was done during the engineering geological mapping of the Klaipėda Strait. The absolute majority of the IR-OSL ages obtained for the investigated inter-till sediments fall within the age range of marine isotope stages (MIS) 5d-5a. The subsequent more detailed examination of geological setting of Quaternary sequence has led to the assumption that the sampled inter-till sediments occur not in situ, i.e. they are found as blocks (rafts) in a thick till bed that have been formed by the ice advance during the Weichselian early pleniglacial maximum (MIS 4). This conclusion does not support the former standpoint that the till beds beneath the bottom of the Klaipėda Strait were formed during the Warthanian (Medininkai, MIS 6) glaciation.

Constraints of Radiocarbon Dating in Southeastern Baltic Lagoons: Assessing the Vital Effects

During the past decades, a suite of radiocarbon (14C), infrared optically stimulated luminescence (IR-OSL), and electron spin resonance (ESR) dates were compiled on a variety of materials from the Curonian and Vistula lagoons and spits of the southeastern Baltic Sea. These dated materials generally included lagoon sediments and mollusc shells, along with samples of fossil fish remains, peat, wood, and water bicarbonates. A growing number of 14C dates (conventional and AMS) demonstrates disparities and contradictions with the associated IR-OSL dates and palaeobotanical investigations of contemporary materials. Detailed analyses of 14C, IR-OSL and ESR chronologies and experimental 14C dating of modern live molluscs and water bicarbonates from the Curonian Lagoon and its main tributary – Nemunas-Neris River system – reveals a substantial influx of “old” carbonates into the lagoon. As a result, the uncertainty of reservoir effect added a considerable error to the 14C ages. Moreover, fossil molluscs of the same species extracted from boreholes and outcrops yield significantly younger ages (up to several millennia) than the enclosing sediments. Both of these trends – aging and rejuvenation – highlight an urgent need for constraining the local reservoir correction (ΔR). Several scenarios are presented to explain the impact of vital effects on radiocarbon chronology of carbonates and to offer strategies to account for them in future studies.