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2 Geological Quarterly

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Relative sea level changes and development of the Hiiumaa Island during the Holocene

Vassiljev J., Saarse L., Grudzinska I., Heinsalu A.

Geological Quarterly

2015

Vol. 59, No. 3

517--530

Three sediment cores (Loopsoo, Tihu, Prassi) from Hiiumaa Island (Estonia) were investigated using diatoms, lithological proxies, magnetic susceptibility, geochronological dates and incorporated with the previously studied Kõivasoo site, aiming to reconstruct the development of the island and shoreline changes during the Litorina Sea and the Limnea Sea. The highest level of the Litorina Sea shoreline near Kõivasoo is at 27.6 m a.s.l., and it occurred during the Initial Litorina Sea. Within the Litorina Sea transgression, 7800 cal yr BP, relative sea level reached 24.9 m a.s.l. at Kõivasoo, 24.1 m a.s.l. at Loopsoo, 23.6 m a.s.l. at Tihu, and 21.5 m a.s.l. at Prassi. Kõivasoo became isolated from the sea about 8500 cal yr BP, Loopsoo between 7100 and 6800 cal yr BP, Tihu around 4800 cal yr BP, and Prassi about 2500 cal yr BP. Presently gained data from Hiiumaa Island confirm that the Litorina Sea regressed consistently during the last 8000 years due to progressively declining isostatic rebound. The present study is also illustrated by 3-dimensional palaeogeographic maps of the Hiiumaa Island development.

Postglacial palaeoenvironmental changesin the area surrounding Lake Udriku in North Estonia

Amon L., Saarse L.

Geological Quarterly

2010

Vol. 54, No 1

85-94

Multiproxy data (plant macrofossils, AMS 14C radiocarbon dates, grain-size distribution, loss-on-ignition and magnetic susceptibility) from Lake Udriku Suurjärv in North Estonia were used to interpret local environmental changes during the postglacial period between 13 800 and 11 000 cal yr BP. Sediment lithology is complex but can roughly be described as silt overlain by silty gyttja, gyttjaand peat. The macrofossil diagram shows the local vegetation development from Late Glacial pioneer communities to early Holocenecommunities. The vegetation succession started predominately with Salix polaris, which was later replaced by Dryas octopetala. Thediversity of plant macrofossils increased significantly during the warmer part of the Allerod. Both the diversity and the number ofplant macrofossils are low in the Younger Dryas, confirming the severe climatic conditions found during this interval. During the LateGlacial to Holocene transition, aquatic taxa prevail among plant macrofossils. The absence of tree remains among macrofossils of thisperiod suggests that trees were not locally present or were not growing near the studied lake. Proxy data indicate several environmental changes. The sediment composition and vegetation reflect cooler and warmer episodes and confirm that the study area has been freeof ice since 13 800 cal yr BP.