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New interglacial deposits from Copenhagen, Denmark: marine Isotope Stage 7

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Author(s)

  • Ole Bennike
  • Lars Hedenäs
  • Kirsty High
  • Joakim S. Korshøj
  • Geoffrey Lemdahl
  • Kirsty Penkman
  • Richard C. Preece
  • Knud Rosenlund
  • Finn A. Viehberg

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Publication details

JournalBoreas
DateAccepted/In press - 16 Jul 2018
DateE-pub ahead of print - 10 Sep 2018
DatePublished (current) - 1 Jan 2019
Issue number1
Volume48
Number of pages12
Pages (from-to)107-118
Early online date10/09/18
Original languageEnglish

Abstract

During a pre-site survey and construction of a new metro route and station in Copenhagen, fossiliferous organic-rich sediments were encountered. This paper reports on multidisciplinary investigations of these organic sediments, which occurred beneath a sediment succession with a lower till, glacifluvial sand and gravel, an upper till and glacifluvial sand. The organic sediments were underlain by glacifluvial sand and gravel. The organic-rich sediments, which were up to 0.5 m thick, accumulated in a low-energy environment, possibly an oxbow lake. They were rich in plant fossils, which included warmth-demanding trees and other species, such as Najas minor, indicating slightly higher summer temperatures than at present. Freshwater shells were also frequent. Bithynia opercula allowed the sediments to be put into an aminostratigraphical framework. The amino acid racemization (AAR) ratios indicate that the organic sediments formed during Marine Isotope Stage 7 (MIS 7), which is consistent with optically stimulated luminescence dating that gave ages of 206 and 248 ka from the underlying minerogenic deposit. The assemblages from Trianglen are similar to interglacial deposits from the former Free Port (1.4 km away) in Copenhagen, except that Corbicula and Pisidium clessini were not found at Trianglen. The presence of these bivalves at the Free Port and the ostracod Scottia tumida at Trianglen indicates a pre-Eemian age. AAR data from archived Bithynia opercula from the Free Port were almost identical to those from Trianglen, indicating that the two sites are contemporary. We suggest the Trianglen interglacial be used as a local name for the MIS 7 interglacial deposits in Copenhagen. MIS 7 deposits have rarely been documented from the region, but MIS 7 deposits may have been mistaken for other ages. The use of AAR ratios in Bithynia opercula has a great potential for correlation of interglacial non-marine deposits in mainland northern Europe.

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© 2018 Collegium Boreas. Published by John Wiley & Sons Ltd. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

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