Jökull - 01.12.1988, Blaðsíða 14

Pétursson (1986) studied the type locality for the
Kópasker Interstadial in northeast Iceland, sug-
gested by Einarsson (1979) to correlate with the
Bölling Interstadial (13.000 - 12.000 BP) in Scandi-
navia. Pétursson dated the deglaciation of that area
to 10.100 BP.
Norðdahl and Hjort (1987), also working in
northeast Iceland, agree with Pétursson’s results.
They date ice retreat from ice-marginal positions in
Vopnafjörður as having occurred c. 10.000 BP.
Our interpretation of the age data, that the Búði
moraine complex is of Preboreal age, raises some
questions regarding ice-marginal positions and
changes in relative sea level during the Late
Weichselian/Preboreal deglaciation of southem Ice-
land. It is interesting to note that Late Weichselian
glaciomarine sediments, frequently encountered in
westem and southwestem Iceland, have not been
reported from southem Iceland. The oldest dated
shell samples from southem Iceland have radiocar-
bon ages of about 10.000 BP (Table II). The most
convincing explanation for this is that the ice
extended beyond the present coastline during the
last part of the Late Weichselian, and thus prevented
any glaciomarine sedimentation there. The recent
investigations cited above indicate similar glacial
advances in other parts of Iceland during the
Younger Dryas Chronozone. We find it probable that
the exposed position of southem Iceland with regard
to cyclonic activity and precipitation caused a major
Younger Dryas ice advance there. A Younger Dryas
ice advance across the Southem Lowlands could
have destroyed evidence of possible Bölling-Alleröd
glaciomarine sedimentation.
Attempts to correlate ice-marginal and strati-
graphic evidence from southem Iceland and from
southwestem - westem Iceland will be the subject of
a separate study. If a Preboreal age for the Búði
moraines is correct it follows that the relative sea
level history of southem Iceland has to be re-
evaluated.
The above results are in agreement with the
suggestion of Ingólfsson (in press) that glaciers
occupied the tributary valleys of Borgarfjörður in
Preboreal time. Our results also indicate that the
glacial retreat from the Búði moraines and ice melt-
ing in the central highlands was rapid in Preboreal
and Boreal time. When the vast Þjórsárhraun lava
flowed from the central highlands around 7800 BP
(Table II: Lu-2610, Hjartarson, 1988) the central
highlands were ice-free.
ACKNOWLEDGEMENTS
We wish to express our gratitude to the Iceland
Scientific Fund for financing the radiocarbon datings
and to the National Energy Authority of Iceland for
the kind permission to use data obtained in investi-
gations of the institute. We also wish to thank dr.
Helgi Torfason, dr. Hreggviður Norðdahl and Helgi
Bjömsson for their critical reading of the
manuscript, Tómas Jóhannesson and dr. Helgi Torfa-
son for correcting the English, Leifur Símonarson
for correcting the mollusc nomenclature and Gyða
Guðmundsdóttir and Olavía Dagnýsdóttir for the
drafting work.
The second author was financially supported by
the Research Council of Sweden.
REFERENCES
Andersen, B.G. 1979: The deglaciation of Norway
15,000-10,000 BP. Boreas 8: 79-87.
Andersen, G.J., J. Heinemeier, H.L. Nielsen, N. Rud,
M.S. Thomsen, S.J. Johnsen, A.E. Sveinbjörns-
dóttir and A. Hjartarson: AMS 14-C dating on
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Askelsson, J. 1934: Kvartárgeologische Studien von
Island I. Geologiska Föreningens i Stockholm
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12 JÖKULL, No. 38, 1988