Efstadalsvatn - A multi-proxy study of a Holocene lacustrine sequence from NW Iceland

Chris Caseldine*, Áslaug Geirsdóttir, Peter Langdon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

69 Citations (Scopus)

Abstract

Multi-proxy data, both lithostratigraphic and biostratigraphic, are presented from Efstadalsvatn, a lake in NW Iceland. The sequence covers the period 10,000 to 3500 14C yr B.P. The biostratgraphic data include the first Icelandic chironomid-based reconstruction of Holocene mean July air temperatures, using a Norwegian training set in the absence of modern Icelandic data. The results show that deglaciation and ecosystem development probably began before 10,000 14C yr B.P. and that July temperatures were around 4°C at ca. 9500 14C yr B.P. Temperatures then rose to ca. 8°C at the time of the deposition of the Saksunarvatn tephra (9100 14C yr B.P.), reaching ca. 10°C by 8500 14C yr B.P., high enough for the growth of tree birch, although successful birch colonisation did not take place until 6750 14C yr B.P. There is some evidence for cooling immediately preceding 9100 14C yr B.P. There is little firm biostratigraphic evidence for the 8200 cal. B.P. event, although this may be due to a relatively low resolution pollen sampling interval, but there are changes at this time in the total carbon (TC) and mass susceptibility (MS) data. Optimal temperatures and relative vegetation stability may have occurred between 8000-6100 14C yr B.P. but the chironomid assemblages indicate higher temperatures after 5000 14C yr B.P. This latter interpretation may, however, reflect delayed colonisation of thermophilous taxa and requires further investigation. There is evidence in the lithostratigraphy for greater local terrestrial instability after 6100 14C yr B.P. but it seems unlikely that this led to the redevelopment of ice in the catchment. The biostratigraphic records appear to show a degree of resistence to climate forcing throughout the early and middle Holocene. The new chironomid-based temperature reconstruction needs to be refined by further studies in Iceland, particularly the development of an Icelandic training set, but has already demonstrated the problems of paleoclimatic interpretations based on pollen and/or macrofossil evidence alone.

Original languageEnglish
Pages (from-to)55-73
Number of pages19
JournalJournal of Paleolimnology
Volume30
Issue number1
DOIs
Publication statusPublished - Jul 2003

Bibliographical note

Funding Information:
Laboratory analyses were carried out both in Exeter and at the INSTAAR sediment laboratory, University of Colorado, Boulder. The core was collected by Jorunn Har)ardóttir and Gu)mundur Helgi Christen-sen and the original research and pollen analyses of the lowermost samples were done by Lisa Doner to whom we are extremely grateful. Later pollen work was in part carried out by Jackie Hatton. We are also grateful to Steve Brooks and John Birks for the use of the Norwegian chironomid-inferred temperature transfer function. Steve Brooks and an anonymous referee are thanked for valuable comments on a previous draft of the manuscript. The research was supported by The Science Funds of the University of Iceland.

Other keywords

  • Chironomids
  • Holocene
  • Iceland
  • Multi-proxy
  • Paleolimnology
  • Paleotemperature
  • Pollen

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