History of the Baltic sea basin from the Eemian to the last glacial maximum
|Location||International Geological Congress,oslo 2008|
|Holding Date||04 October 2008|
The Baltic Sea Basin (BSB) is one of the world’s largest intra-continental basins, presently occupying 373,000 km2 and with a drainage area four times its size. BSB has served as depositional sink throughout its geological history and accumulated sediments comprise a unique high-resolution paleoenvironmental archive where the history of the drainage area and the basin itself is preserved. Sediments of the largest European intra-continental basin, the BSB, form an archive for past and present climate. The geographic location of the BSB also makes it a unique link between the northwest European terrestrial climate records and those from the North Atlantic.
The BSB has undergone several glaciations during the Quaternary. During the last interglacial (the Eemian) a sea, which was larger and more saline than the present Baltic Sea, occupied the BSB. An almost complete marine Eemian sediment sequence has been found dislocated in a coast cliff in the western Baltic, but no complete sequence of sediments deposited in the Eemian has been recovered in situ in any part of the Baltic Sea. Consequently we do not know the history of this sea during the termination of the Eemian interglacial. Two subsequent early Weichselian glacial advances (MIS-5d and MIS-5b) may only have reached as far south as c. 60.5°N leaving the central and southern BSB free of ice. Glacial event during MIS-4 has been recorded in sediments from Ostrobothnia Finland c. 64°N. Thus it is probable that an isolated lake covered large parts of the BSB until c. 40 kyr BP. This portion of the BSB filled in with sediments during MIS-5d to MIS-3, and the accumulated sedimentary archive most likely registered climate-related changes in the huge catchments of BSB with a very high resolution. There is ample evidence from the Danish glacial stratigraphy that the southern BSB experienced an oscillating ice margin and was partly free of ice at several occasions at the end of MIS-3 prior to LGM at c. 20 kyr BP when the Weichselian ice sheet covered the entire BSB.
The deglaciation of the southern BSB between 22-16 kyr BP was very complex, with major deglacial phases interrupted by some intriguing still-stands and even re-advances. The lake dammed in front of the retreating ice front, the Baltic Ice Lake (BIL), released huge amounts of freshwater into the North Atlantic during the early stage of the deglaciation between c. 16 and 11.5 kyr BP.
As we know from the seismic records that sediment sequences spanning the last glacial cycle exists in the BSB a consortium of circum Baltic researcher have submitted a drilling proposal to the IODP. The outcome of such a drilling project will increase our understanding of the history of the BSB and its interaction with the climate development in the North Atlantic region during the last c. 130 000 years.