Was southern Sweden ice free at 19-25 ka, or were the post LGM glacifluvial sediments incompletely bleached?

Summary, in English

Glacifluvial deposits along an ice-marginal zone,in Smaland, southern Sweden, have been dated using post-IR blue OSL. To test for incomplete bleaching, we adopted two strategies: analysis of modern analogues and small-aliquot dose distributions. Samples of modern fluvial sediments show no significant incomplete bleaching; they yield equivalent doses of only 0.5-2 Gy (similar to 0.25-4% of our glacifluvial sediment doses). Small-aliquot dose distributions do not provide any evidence for incomplete bleaching. The sediments are believed to have been deposited during deglaciation and appear to fall into two age groups: 19-25 ka (mainly sandur sediments) and 33-73 ka (mainly deltaic sediments). Compared to the expected ages (13-15 ka), even the younger glacifluvial OSL ages appear up to 10 000 years (similar to 25 Gy) too old. The ages are nevertheless stratigraphically consistent and correspond between sites; we deduce that the 19-25 ka ages are true deposition ages. For glacifluvial sedimentation to take place on the South Swedish Upland at this time either a very early deglaciation is required, or alternatively ice-free conditions just prior to the LGM. The deltaic sediments (33-73 ka) were most likely not significantly bleached during deposition and thus they date events prior to the latest ice advance. (c) 2006 Elsevier Ltd. All rights reserved.

• Author: Helena Alexanderson; Andrew S. Murray
• Publishing year: 2007
• Language: English
• Pages: 229-236
• Publication/Series: Quaternary Geochronology
• Volume: 2
• Issue: 1-4
• Links: http://dx.doi.org/10.1016/j.quageo.2006.05.007
• Document type: Journal article
• Publisher: Elsevier
• Topic: Geology
• Keywords: OSL; glacifluvial; Sweden; Weichselian
• Status: Published
• ISBN/ISSN/Other: ISSN: 1871-1014