Lateglacial-Middle Holocene environmental dynamics in the coastal area of the Baltic sea: a new insight for the territory of Lithuania

ENTo take a new look at the Lateglacial-Middle Holocene environmental history in the maritime region of the territory of Lithuania, we have synthesized geological-geomorphological, geochronological, sedimentological and palaeobiological data representing the Lithuanian maritime region. The published information was coupled with new data obtained within the framework of the project “Man and Baltic Sea in the Meso-Neolithic: Relict Coasts and Settlements Below and Above Present Sea Level. ReCoasts&People”, which included the archaeological record as well. Based on the collected data we propose refined reconstruction of the paleoenvironmental history in this part of the Baltic, including dynamics of the Baltic Sea coast. The development of the proglacial lakes that existed during the initial intervals of the Lateglacial, forming erosional terraces discovered at about 40 m a.s.l. in the southern part of the maritime region, was succeeded by a period of low water estuaries or freshwater lagoons that occurred after 13.8 cal kyr BP (11.7 cal kyr BC) in this part of the region. While in the northern sector of the maritime region, pronounced ridge stretching at about 12-16 m a.s.l. was formed by the Baltic Ice Lake according to geomorphological and sedimentological data. New evidence, particularly isotopic and palaeobiological data, demonstrate that remarkable transformations of the coastal zone started at the Lateglacial-Holocene transition when the seacoast of the Yoldia Sea was situated further westwards and the terraces of this water body were detected laying 11 to 24-29 m b.s.l. even.At that time, the terrestrial sedimentation had predominated all along the Lithuanian maritime region. Numerous imprints of biogenic origin (submerged pine trees and peat enriched sediments) discovered at about 30-32 m b.s.l. point to transgression of the basin at about 10.1-10.2 cal kyr BP (~8.2 cal kyr BC) marking the time of the maximum transgression of the Ancylus Lake, the next stage in the history of the Baltic Sea. Nevertheless, the tendency of a negative water level predominated in the coastal region throughout the final part of the Ancylus stage and the Initial Litorina Sea stage, i.e. until 8.5 cal kyr BP (6.4 cal kyr BC). Only during the second Littorina transgression (7.7-7.6 cal kyr BP/5.8-5.7 cal kyr BC) were certain areas in the northern and central parts of the maritime region submerged. The marine terraces, then varying between 2-8 m a.s.l., were formed due to the subsequent glacioisostatic rebound of the maritime region. Even at that time terrestrial sedimentation predominated in the southern part of the region where formation of the extended peatbogs had started since the Early Holocene onward. Keywords: Lithology, Pollen, Diatoms, Molluscs, 14C, l0Be, OSL, Geology, Geomorphology, Lithuanian maritime region. [From the publication]

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