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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.

Simulation of proglacial lake shore displacement in Estonia

Vassiljev J., Saarse L., Miidel A.

Geological Quarterly

2005

Vol. 49, No. 3

253-262

The Late Glacial shoreline database compiled for Estonia covers 149 sites on the proglacial lakes A1 (Voose) and A2 (Kemba). Eighty-two sites were used in further simulations. Point kriging interpolation with a linear trend approach was applied to create interpolated surfaces of water levels for checking the spatial correctness of data. The sites with altitudes visually not matching with sites nearby were discarded, as well as those with residuals of more than 1 mand 0.7 mrespectively. The final surfaces were analysed geostatistically by simulating isobases, direction of tilting, and shoreline gradient. The simulated isobases suggest that both proglacial lakes A1 and A2 were connected with the glacial lake in the Lake Peipsi basin. The interpolated surface aspect shows that the direction of tilting varies between 320° and 340°. The surface gradient of lake A1 is highest in the NW and SE parts of the study area (50 and 25 cm km-1, respectively), and that of lake A2 is highest in the NWand SE parts (40 and 20 cm km-1, respectively). Using the modelling data, the shoreline correlation between the two proglacial lakes has been revised.