MIS 3 sediment stratigraphy in southern Sweden sheds new light on the complex glacial history and dynamics across southern Scandinavia

Abstract

Recent studies have revealed that areas with sediments pre‐dating the Last Glacial Maximum (LGM) are more common in southern Scandinavia than previously thought. To describe and date these sediments, four deep core drillings were made in the province of Småland and one in the province of Skåne, southern Sweden, and an existing sediment core drilled in the 1960s from western Skåne was re‐examined and re‐dated, all resulting in a total of 22 AMS 14C ages and 19 OSL ages. With some variation, the Småland cores revealed a stratigraphy consisting of two tills separated by proglacial glacifluvial and glaciolacustrine sediments, dated to between 46 and 25 ka BP (Marine Isotope Stage (MIS) 3 to 2). We suggest that these sediments were deposited during the ice retreat of the MIS 3 Ristinge glaciation over southern Scandinavia and the subsequent re‐advance over the area in late MIS 3 and the transition to MIS 2, when the Fennoscandian Ice Sheet advanced towards its LGM marginal positions. This contrasts with the glacial history of southernmost Skåne, where an additional MIS 3 glacial advance through the Baltic Basin is suggested by the occurrence of a till named Allarp Till. New ages from sediments under‐ and overlying this till suggest that it was deposited by the same Baltic ice advance that deposited the Klintholm till in Denmark (Klintholm Advance, c. 34–30 ka).

Proposing a new conceptual model for the reconstruction of ice dynamics in the SW sector of the Scandinavian Ice Sheet (SIS) based on the reinterpretation of published data and new evidence from optically stimulated luminescence (OSL) dating

“…All data are based on quartz OSL measurements on large aliquots. These ages are in good agreement with the timing of the Young Baltic ice advance documented by the stratigraphically youngest tills found at Kriegers Flak and in the Alnarp Valley and dated to about 20 ka at Kriegers Flak (Anjar et al, 2014;Möller et al, 2020). The stratigraphical record at Adlergrund is less clear.…”

“…Evidence for an early MIS 3 ice advance of the SIS is only present to the north-west of an idealized line from Bornholm following the Rønne Banke to the Adlergrund site and the western part of the island of Rügen. (b) Decay of the SIS after the early MIS 3 advance after 50 ka, dated, for example, by Anjar et al (2014) and Möller et al (2020) in south-western Sweden. Deglaciation reached the depicted area most likely very shortly after 50 ka; however, uncertainties in the data do not currently allow for a more precise dating.…”

“…(c) Early MIS 3 advance of the Baltic Ice Stream of the SIS split into two lobes by the horst of Bornholm. The advance to the west is known as the Klintholm Advance, dated in the Alnarp Valley by Anjar et al (2014) and Möller et al (2020) and at Kriegers Flak by Anjar et al (2014). The advance of the south-western Oder Lobe into northern Germany is known as the Brandenburg Advance and was dated in multiple studies.…”

“…It cannot be excluded that the Klintholm Till and the Allarp Till are related to the same ice advance. Möller et al (2020) recently dated glaciofluvial and glaciolacustrine deposits from different sites in the Alnarp Valley bracketing that till using quartz OSL and radiocarbon dating, establish-ing a time frame for the ice advance and subsequent deglaciation of between 34 and 30 ka.…”

“…The lower till bed is correlated with the Ristinge Till at an age older than 50 ka (Anjar et al, 2014). Möller et al (2020) recently published numerical data based on quartz OSL and radiocarbon ages from glaciofluvial and glaciolacustrine deposits associated with the deglaciation from the Ristinge Advance. These ages all post-date the presumed age of the Ristinge Advance, thus indirectly confirming it.…”