Research > Baltic Sea during the last ice age

The Baltic Sea basin during the last ice age

sediment core
Sediment cores from Kriegers Flak in the SW Baltic Sea.

The last glacial period (the Weichselian, 115-11.7 ka) is characterized by major glaciations on the northern hemisphere. By studying the traces of these past ice sheets we get a unique opportunity to study the dynamics of an ice sheet over large timescales, such as an ice age cycle, and during highly variable climate conditions.

Pieces of soft, white, chalk have been picked up by the ice sheet and mixed with the other sediments.

In this project Middle Weichselian sediments were studied in sediment cores from Kriegers Flak, a shallow area in the southwestern Baltic Sea.

In the lowermost and oldest part of our sediment cores we found a soft chalk bedrock overlain by the oldest till identified on Kriegers Flak. We suggest that this till, which we dated to the Early or Middle Weichselian, was deposited during the Ristinge advance, which implies an age of c. 55-50 ka.

Foraminiferas. The red line is 1 mm long.

Following the deglaciation after this advance, isostatic depression enabled a marine influence in the southern Baltic Basin. A clay unit with a low-diversity benthic foraminifera fauna indicative of cold water and low salinities, was deposited. This period was followed by a forced regression on Kriegers Flak, probably caused by a combination of isostatic rebound and a falling global sea level, which led to a period of nondeposition and erosion.

Between 42 and 36 cal. ka BP, wetlands and shallow lakes existed on Kriegers Flak. Macrofossil and pollen analyses suggest tundra-like, or forest tundra-like vegetation, possibly with birch and pine in sheltered locations.

From 28.5 to 26 ka, a thick succession of glaciolacustrine clay was deposited at Kriegers Flak indicating a damming the Baltic Basin by an ice advance into Kattegat.

A better understanding of the Weichselian history of the Baltic Sea basin was also one of the goals of the IODP (International Ocean Discovey Program) campaign in the Baltic Sea during 2013. Their results can be found at the IODP web page.

Anjar, J., Adrielsson, L., Larsen, N. K., Möller, P. & Barth, K. in press: Weichselian glaciation history of the Fennoscandian Ice Sheet in southern Sweden and the southwestern Baltic Basin. Boreas DOI: 10.1111/bor.12048. Link

Anjar, J., Adrielsson, L., Bennike, O., Björck, S., Filipsson, H. L., Groeneveld, J., Knudsen, K. L., Larsen, N. K. & Möller, P. 2012: Palaeoenvironments in the southern Baltic Sea Basin during Marine Isotope Stage 3: a multi-proxy reconstruction. Quaternary Science Reviews 34, 81-92. Link

Anjar, J., Larsen, N. K., Björck, S., Adrielsson, L. & Filipsson, H. L. 2010: MIS 3 marine and lacustrine sediments at Kriegers Flak, southwestern Baltic Sea. Boreas 39, 360-366. Link

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