Jökull - 01.12.1990, Side 97

arfjörður and Hvalfjörður regions, W-Iceland and on
Melrakkaslétta in N-Iceland. These sediments demon-
strate that at that time (Bölling) the climate had im-
proved considerably so that parts of Iceland were ice-
free and due to melting of glaciers the sea level had
nsen and transgressed on land that was left suppressed
by the weight of the glaciers. Alleröd-age marine sed-
iments from the Reykjavík region, Hvalfjörður and
Borgarfjörður demonstrate further improvement of the
climate. No marine sediments have however been ob-
served with certainty of Younger Dryas age, despite
considerable search. The lack of shells from that time
mdicate severe glaciation of the country in the Younger
Dryas period. In addition to this evidence for the Late
Weichselian oscillations, é180 measurements on shells
from late glacial sediments of known age in S and W
Iceland suggest similar temperature-pattem to that re-
vealed by the isotopic composition of the Greenland
ice and the lake sediments from Switzerland.
acknowledgement
Radiocarbon dating projects are currently in
progress in cooperation with Jan Heinemeier and Niels
Rud at the tandem accelerator laboratory, University
°f Aarhus. We thank them for allowing us to use un-
published data on Icelandic molluscs. Some of the ra-
diocarbon dates are parts of projects done in coopera-
tion with Icelandic geologists Ámi Hjartarson, Áslaug
Geirsdóttir, Hreggviður Norðdahl and Jón Eiríksson.
We acknowledge the use of this data for the purpose
°f the present paper. We would also like to thank Karl
Grönvold at the Nordic Volcanological Institute and
Jón Eiríksson at the Science Institute, University of
Iceland, for critically reading the manuscript and for
utany valuable suggestions.
REFERENCES
Andersen, G. J., J. Heinemeier, H. L. Nielsen, N.
Rud, M. S. Thomsen, S. J. Johnsen, Á. E. Svein-
bjömsdóttir and Á. Hjartarson 1989. AMS 14C
dating on the Fossvogur sediments, Iceland. Ra-
diocarbon 31,592-600.
Broecker, W. S. and G. H. Denton 1989. The role
of ocean-atmosphere reorganizations in glacial
cycles. Geochim. Cosmochim. Acta 53, 2465-
2501.
Boyle, E. A. 1988. Cadmium chemical tracer of deep-
water. Paleoceanography 3, 471-489.
Boyle, E. A. and L. Keigwin 1987. North Atlantic
thermohaline circulation during the past 20,000
years linked to high-latitude surface temperature.
Nature 330, 35-40.
Craig, H. 1961. Isotopic variations in meteoric water.
Science 133,1702-1703.
Craig, H. 1965. The measurement of oxygen isotope
paleotemperatures. Proc. Spoleto Conference on
stable isotopes in oceanographic studies and pa-
leotemperatures 3.
Dansgaard, W. 1964. Stable isotopes in precipitation.
Tellus 16, 436-468.
Dansgaard, W., S. J. Johnsen, H. B. Clausen and
N. Gundestrup 1973. Stable isotope glaciology.
Meddelelser om Grönland 197, 1-53.
Dansgaard, W., H. B. Clausen, N. Gundestrup, C. U.
Hammer, S. J. Johnsen, P. M. Kristinsdóttir and
N. Reeh 1982. A new Greenland deep ice core.
Science 218,1273-1277.
Dansgaard, W., H. B. Clausen, N. Gundestrup, S. J.
Johnsen and C. Rygner 1985. Dating and Climatic
interpretations of two deep Greenland ice cores.
In: Greenland Ice Core: Geophysics, Geochem-
istry, and the Environment (eds. C. C. Langway,
Jr., H. Oeschger, and W. Dansgaard). Am. Geo-
phys. Union, Geophys. Monograph 33, 71-76.
Dansgaard, W., S. J. Johnsen, H. B. Clausen, D.
Dahl-Jensen, N. Gundestrup, C. U. Hammer and
H. Oeschger 1984. North Atlantic climatic oscil-
lations revealed by deep Greenland ice cores. In:
Climate Processes and Climate Sensitivity (eds.
J. E. Hansen and T. Takahashi). Am. Geophys.
Union, Geophys. Monograph 29, Maurice Ew-
ing Series 5, 288-298.
Dansgaard, W., J. W. C. White and S. J. Johnsen 1989.
The abrupt termination of the Younger Dryas cli-
mate event. Nature 339, 532-534.
Duplessy, J. C., N. J. Shackleton, R. G. Fairbanks,
L. Labeyrie, D. Oppo and N. Kallel 1988. Deep-
water source variations during the last climatic
JÖKULL, No. 40, 1990 93