Lithostratigraphical work at more than hundred localities across the Arkhangelsk Region has resulted in a new glaciation history for the region. For the Weichselian we have identified four major glaciations with advances с 100-90, 70-65, 55-45 and 20 kyr BP. The location at the junction between the Scandinavian and the Barents and Kara Sea ice sheets yields ice movement directions in the Arkhangelsk Region between W, NW and NE. Changes in ice flow direction have proven to be important for identifying ice advances of different age.

The Middle Weichselian ice advances are separated by a marine event dated to around 60 kyr BP - the Mezen Transgression. Deposits of the Mezen transgression found along the Kuloi Coast, in the Mezenskaya Guba and along the Chyoshkaya Guba have become an important correlation tool within the Arkhangelsk Region. The deposition took place in a wide range of marine/coastal environments from offshore to wave- and tide dominated shoreface to beach and shallow lagoons. The marine fauna suggests a climate somewhat colder than today, but not severe, indicating a full deglaciation between the two ice advances. The Mezen Transgression is probably also recorded in the fluvial depositional system as an aggradational phase around 60 kyr BP. Relative sea level during the Mezen Transgression was at least 40 m above present in the eastern Arkhangelsk Region suggesting flooding up to 300 km inland from the present coast in the Arkhangelsk as well as the Pechora regions. OSL dates from the Mezen Transgression deposits yield ages in a narrow time interval around 60 kyr BP. The deposits are found both above till indicating ice movement from NW and below till showing ice flow from NE. Glaciotectonic deformation before and after the marine deposition show the same shift in ice flow directions. Tidal deposits of Eemian age are also known from the Arkhangelsk Region, but can be distinguished from the Mezen Transgression based on lithostratigraphy, fauna and OSL ages.

The current reconstruction of ice configurations suggests closing of the White Sea entrance and damming of rivers around 70-65 and 20 kyr BP. Lacustrine basins and evidence for riverine flow reversal have been found on the Severnaya Dvina and along the north coast of the Kanin Peninsula in association with the 20 kyr BP advance of the Scandinavian and Barents Sea ice sheets. Sedimentological evidence of the «White Sea lake» associated with the 70-65 kyr BP advance of the Barents Sea ice sheet have been absent until recently. During the field season 2006 we found fine-grained lacustrine deposits in sections on the Vychegda and the Upper Severnaya Dvina rivers. In some exposures up to four lacustrine units have been found in superposition. The units are separated by granular horizons indicating rapid drainage. Hummocky cross bedding formed during storm events suggests lake basins of a significant size. Further work on the lacustrine systems of this region is planned for 2007 and forms part of our current focus on sea level, fluvial/coastal depositional systems and the link between the terrestrial and the marine records.

Reference:

Jensen M., Demidov I.N., Larsen E., Lysa A. Weichselian glaciers, lakes and sea level in the Arkhangelsk region: correlation potential and challenges. Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 44.