Palaeoenvironments in the southern Baltic Sea Basin during Marine Isotope Stage3:A multi-proxy reconstruction

• Published in: Quaternary Science Reviews
• Main Authors: Anjar, Johanna, Adrielsson, Lena, Bennike, Ole, Björck, Svante, Filipsson, Helena L., Groeneveld, Jeroen, Knudsen, Karen Luise, Larsen, Nicolaj Krog, Möller, Per
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Baltic Sea Basin; Marine Isotope Stage 3; Palaeoenvironment; Scandinavian Ice Sheet; Kattegat; Ice Sheet; Tundra
• Online Access: https://curis.ku.dk/portal/da/publications/palaeoenvironments-in-the-southern-baltic-sea-basin-during-marine-isotope-stage3(43a2d890-5c90-4578-a444-0680d0f9b747).html; https://doi.org/10.1016/j.quascirev.2011.12.009

Sediment cores from Kriegers Flak in the southwestern Baltic Sea provide a unique possibility to study the Middle Weichselian history of the Baltic Basin. Three Weichselian interstadial units have been identified and are attributed to Marine Isotope Stage 3 (MIS 3, 60-25ka). The oldest unit A is characterized by a deglaciation sequence, gradually turning into brackish-water clay. The low-diversity benthic foraminiferal fauna, stable oxygen isotope values and Mg/Ca ratios indicate low temperature and salinity for unit A. A hiatus separates unit A from the overlying unit B, which was deposited in wetlands and shallow lakes between 42 and 36cal.ka BP. Macrofossil and pollen analyses indicate deposition of unit B in an area dominated by a tree-less open tundra environment, possibly with some birch and pine in sheltered positions. The uppermost unit C is characterized by clay deposition, including redeposition of material from older sediments (unit B). Optically stimulated luminescence (OSL) ages indicate deposition of unit C between 26 and 28.5ka. Radiocarbon ages of 39 and 40cal. ka BP for unit C are considered to be too old. The following depositional model is suggested: (I) Isostatic depression of the region after an advance of the Scandinavian Ice Sheet (SIS), most likely the Ristinge ice advance, previously dated to c. 55-50ka, enabled an inflow of marine waters into the Baltic Basin during the deposition of unit A. (II) Isostatic rebound caused a regression at Kriegers Flak, and a hiatus between units A and B. (III) Wetlands and smaller lakes formed in the uplifted area between 42 and 36cal.ka BP (unit B). (IV) Deposition of glaciolacustrine clays at Kriegers Flak demonstrates that a growing SIS dammed Kattegat and the Baltic Basin c. 28.5 to 26ka. The new evidence from Kriegers Flak provides a solid framework for future MIS 3 palaeoenvironmental reconstructions in the circum-Baltic area.