Jökull - 01.12.1989, Blaðsíða 28

carbon (14C) being 5568 years. The radiocarbon age
is calculated from the year 1950, and corrected for
13C/12C and the apparent age of the sea.
Ifí Table I, the ages of the shell samples are shown
as measured in the laboratory, and also corrected for
the apparent age of the sea. It is necessary to sub-
tract the age of the sea from the measured age of the
samples if they are to be compared with terrestrial
samples (plants) or shell samples from other parts of
the world. Some measurements have been made of
the apparent age of the sea around Iceland
(Broecker and Olson, 1961; Krog and Tauber, 1973;
Hákansson, 1983). The results are somewhat vari-
able, but the most careful and recent ones indicate
that the apparent age of the sea around Iceland is
365+20 years (Hákansson, 1983). If the apparent
age of the sea is estimated to have been the same
toward the end of last glaciation, the age of the
shell-bearing section of Fossvogur layers at Naut-
hólsvík and Skerjafjörður will be about 11,000 years
BP. The age of the samples is 11,435 to 10,765 years
BP. The average age of the samples from Nauthóls-
vík is about 11,200 years BP, and 10,900 years BP
for samples from Skerjafjörður. This difference is
normal. At Nauthólsvík, the shell samples were col-
lected from the middle of the marine sediment,
whereas at Skerjafjörður, they were collected from
the top of the marine sediment, just under the over-
lying till.
The traditional radiocarbon measurement from
1987 (Lu-2599 in Table I) and the accelerator meas-
urements from 1988 (all the AAR samples in Table
I) are very consistent and the precision of the meas-
urements is good. Einarsson’s radiocarbon date from
the University area (line 5 in Table I) shows a simi-
lar age. These data strongly indicate that the shell-
bearing section of the Fossvogur layers at Nauthóls-
vík, Skerjafjörður and the University area are from
the Alleröd Interstadial and early Younger Dryas at
the end of the last glaciation and not from the Eem
Interglacial.
It is obvious that the uppermost till of the Foss-
vogur layers was formed by a glacier that overrode
these layers at the end of the Ice Age. The last gla-
cial advance of the Weichselian glaciation occurred
TABLE II. Geological time-scale. According to this
paper and Hjartarson and Ingólfsson (1988) the con-
ventional Icelandic names should be changed.
TAFLAII. Tímatal. Hinum hefðbundnu íslensku
nafngiftum þarf að breyta ef niðurstöður þessarar
greinar og nýjar aldursgreiningar á Búðaröðinni
(Hjartarson og Ingólfsson, 1988) reynast réttar.
Age BP millenium English name Conventional Icelandic names Climate
10-9 Preboreal Birkilausa sk. warm
11-10 Younger-Dryas Búðastig cold
11.8-11 Alleröd Saurbæjarstig warm
12-11.8 Older-Dryas Alftanesstig cold
13-12 Bölling Kópaskersstig warm
during Younger Dryas (see Table II). It followed the
warm Alleröd Interstadial, which ended about
11,000 years ago. The extent of glaciers towards the
end of this glaciation, and in early Holocene, has
been investigated all over Iceland in the past decade
(Hjartarson and Ingólfsson, 1988; Hjartarson and
others, 1981; Ingólfsson, 1985, 1988; Ingólfsson and
Hjort, 1988; Pétursson, unpublished; Kaldal, unpub-
lished, 1978; Norðdahl, 1983; Norðdahl and Hjort,
1987; Norðdahl and Einarsson, 1988; Víkingsson,
1978. See also the conference papers: Isaldarlok á
Islandi, 1987; Environmental Change in Iceland,
Past and Present, 1988). The extent of the glaciers
is, however, far from being completely known yet. It
has been a common opinion, that the main ice sheet
of the Younger Dryas lay on the southem part of the
Central Highlands, and that the Búði end-moraines
indicate its margin in Southern Iceland (Kjartans-
son, 1943; Einarsson, 1968; Einarsson and Alberts-
son, 1988). Recent investigations, however, point to
a considerably heavier Younger Dryas glaciation in
South Iceland (Hjartarson and Ingólfsson, 1988).
26 JÖKULL, No. 39, 1989