Náttúrufræðingurinn - 1978, Page 14

Sesmundsson, Krislján ir Noll, H., 1975:
K/Ar ages o£ rocks froni Húsafell,
Western Iceland, and tlie develop-
ment of the Húsafell central volcano.
Jökull, 24, 40-57.
Zagiuijn, W. H., 1974: The Pliocene-
Pleistocene boundary in Western and
Southern Europe. Boreas, 3, 75—97.
SUMMARY
Some Notes on the Age of the
Tjörnes Strata Sequence,
Northern Iceland
by Dr. Kristinn J. Albertsson,
Science Institute, University of lceland.
A few new K/Ar dates froni Tjörnes,
Northern Iceland, are presented and a
brief outline is given of interpretations
of age relations by previous workers in
this area. The Tjörnes peninsula com-
prises a thick sequence of alternating
marine and terrestrial sediments and sub-
aerial lava flows. The lower part o£ the
sequence consists chiefly of sediments in-
corporating fossiliferous horizons of Plio-
cene age as inferred from correlations of
tliese witli fossiliferous sediments else-
where.
The upper part of the sequence com-
prises 10 glacial horizons. Radiometric
ages presented here confirm previous
postulations as to the position o£ geo-
magnetic boundaries, showing 0.75 ±0.10
Ma for the Brunhes/Matuyama boundary
and bracketing the Matuyama/Gauss
boundary witli 2.55 ± 0.27 Ma for a
normally magnetized lava flow and 2.36 ±
0.16 Ma for a reversely magnetized lava
flow on top with a conglomerate bed
separating the two. Four discrepant ages
from the lower part of the Máná basalt
series are reported. Together they yielded
an “isochron” age of about 1.2 Ma.
Glaciation down to sea level in the
Tjörnes area is seen to have been reached
about 2 Ma although inland glaciations
had been initiated more than one million
years earlier.
8