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Fig. 9.3 BIL 12,700 cal. years BP, stage A 2 . Isobases show the reconstructed water level above
present sea level in metres. Black dots show the location of used shoreline sites
the Palivere ice-marginal zone to the Salpausselkä I endmoraines, considerable rear-
rangement of the proglacial lake drainage system occurred in Estonia: connection
of Lakes Võrtsjärv and Peipsi with the BIL was terminated via straits and these
lakes started to develop as isolated water bodies (Fig. 9.4 ) . The water bodies in
Lakes Peipsi and Võrtsjärv were most likely slightly larger than shown in Fig. 9.4 ,
because their thresholds were about 0.5-2 m higher than BI water level in Baltic
Sea basin. The exact location of Lake Võrtsjärv threshold is difficult to determine
because of the relief flatness: its altitude is about 42 m a.s.l. The BIL water level
at threshold was about 40.5
1 m a.s.l. Lake Peipsi threshold was located at the NE
end of the lake. Its altitude was at minimum 28 m a.s.l. as limestone surface, which
however at that time was covered by sandy deposits, so that the maximum altitude
of the threshold was about 34 m a.s.l. The BIL water level at threshold was about
31
±
1 m a.s.l., so that Lake Peipsi could have very shallow connection with BIL
depending on the exact threshold altitude. In NW Russia, BIL extended to the Lake
Ladoga basin over Karelian Isthmus and Neva valley. However, the strait in Neva
valley was considerably narrowed compared to the previous stage A 2 .
±
 
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