Eemian crustal deformation in the eastern Baltic area in the light of the new sites at Peski, Russia and Pohja-Uhtju, Estonia

摘要

Several Eemian (Mikulino) marine deposits are known from the northwestern part of Russia and from Estonia. The best-known deposits are situated at Mga, Russia and at Prangli, Estonia. Two new sites with clayey and silty deposits covered by till were studied for pollen and diatoms at Peski, Russia and Pohja-Uhtju, Estonia. At Peski, the deposit representing the Eemian Interglacial is 3.8m thick at the depth of 13.4-9.6m above present sea-level. At Pohja-Uhtju, the deposit representing the Eemian is 3.5m thick at the depth of 47.9-51.4m below present sea-lcvcl. Although Peski is situated at a higher altitude than Pohja-Uhtju at present, the diatom stratigraphy at these sites indicates deeper and more saline conditions in the Peski area than at Pohja-Uhtju during the Eemian. This result is similar to some previous studies, which indicate, that although the Russian deposits (e.g. Peski, Mga) are now at a higher altitude than those in Estonia (Pohja-Uhtju and Prangli), the diatoms in the Russian deposits are indicative of a considerable depth of water during the time of deposition. These deposits suggest that the Eemian shore levels ascend from Estonia eastwards, while the Late Weichselian and Holoccnc shorelines tilt downwards in the same general direction. The present material from Estonia and northwestern part of Russia shows marked differences between the Eemian and Late Weichselian/Holocene crustal deformations, which probably resulted from different ice loads during the final glaciation phases and probably also from different deglnciation patterns during the Saalian and Late .Weichselian.