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Helena Alexandersson

Helena Alexanderson

Professor

Helena Alexandersson

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

Författare

  • Helena Alexanderson
  • Andrew S. Murray

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.

Publiceringsår

2007

Språk

Engelska

Sidor

229-236

Publikation/Tidskrift/Serie

Quaternary Geochronology

Volym

2

Issue

1-4

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Geology

Nyckelord

  • OSL
  • glacifluvial
  • Sweden
  • Weichselian

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1871-1014