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SUMMARY
Early Pleistocene environmen-
tal changes at the north coast
of Iceland caused by glacial
interglacial cyclicity
by
Jón Eiríksson1, Karen Luise Knudsen2
and Már Vilhjálmsson3
The climate around Iceland is to a large
extent controlled by the North Atlantic
Current. In the present paper, sedimentary
facies, foraminifera, and molluscs are used
to reconstruct environmental conditions
during the accumulation of the 1.5 Ma old
Svarthamar Member unit frorn the Tjörnes
sequence, North Iceland. The Tjörnes se-
quence and the Breidavík Group in partic-
ular contains a unique record of Cainozoic
glacier variations in the North Atlantic.
This is reflected in lithological variations
where marine and terrestrial sediments are
intercalated between lava flows and pyro-
clastic rocks on Tjörnes Peninsula. Our
results from the Svarthamar Member show
that the lithological cycle from glacial to
proglacial and then to shallow marine sed-
imentation coincide with faunal succes-
sion reflecting a change from arctic to
boreal arctic or even boreal conditions in
the sea around lceland just after the
Olduvai event of the Matuyama. The am-
plitude of this climatic cycle is compara-
ble to the Late Pleistocene glacial-inter-
glacial cycles in the North Atlantic. This
indicates that the North Atlantic current
crossed the Greenland-Iceland and Iceland-
Faroe ridges during interglacials resulting
in a periodic northward shift of the polar
front during at least a part of the Early
Pleistocene.
'Science Institute, University of Iceland
Jarðfrœðahús Háskólans
IS-101 REYKJAVÍK
Iceland
2Geological Institute
University of Aarhus
DK-8000 ÁRHUS C
Denmark
3Fjölbrautaskólinn i Garðabæ
Lyngás 7-9
1S-210 GARÐABÆR
Iceland
177