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Jüri Vassiljev, Institute of Geology at Tallinn University of Technology (Estonia)
Leili Saarse, Institute of Geology at Tallinn University of Technology (Estonia)
Alar Rosentau, Institute of Geology at Tallinn University of Technology (Estonia)
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A shoreline database of the Baltic Ice Lake (BIL) for eastern Baltic, including more than 1200 sites, was compiled. The database covers Estonia, Latvia, southern Finland and NW Russia. The data were interpolated to the water level surfaces using the point kriging approach for 5 different stages of the BIL: A1, A2, BI, BII, BIII, with ages ca 13,300, 13,000-12,800, 12,300-12,100, ca 12,000 and 11,600 cal yr BP respectively. The ages are grounded on biostratigraphical records, varve counts and on correlation of ice marginal zones, because 14C dates from the coastal formation are absent due to lacking of suitable material for dating. The highest shoreline of the BIL (A1 in Estonia) was formed concurrently with or before the formation of the Pandivere ice marginal zone ca 13,300 cal BP and the lowest modelled shoreline BIII corresponds to the BIL level prior the drainage at Billingen.
Spatial check showed that some shoreline sites are either too high or too low compared to the neighbouring sites and they were eliminated from the simulations. The interpolated water-level surfaces were then smoothed using residuals (the difference between the actual site altitude and the interpolated surface) and sites with residuals more than ±1 m were discarded. The BIL shorelines and bathymetry were then reconstructed using a GIS approach, where interpolated surfaces of water level were removed from the modern digital terrain model (DTM). Reconstructed shorelines and bathymetry show that during stages A1 and A2 the BIL extended to the basins of large lakes Vrtsjärv and Peipsi (Estonia) and probably also to Lake Ladoga (Russia). Palaeogeographical reconstructions indicate that lakes Vrtsjärv and Peipsi isolated from the BIL between 12,400 and 11,700 cal yr BP, most likely between 12,400 and 12,100 cal BP as can conclude from the reconstructed water level curves, based on biostratigraphical data from the southern parts of both lakes.
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