Jökull - 01.12.1988, Page 3

Preboreal Glaciation of Southem Iceland
ÁRNI HJARTARSON
National Energy Authority,
Grensásvegi 9,108 Reykjavík, Iceland.
ÓLAFUR INGÓLFSSON
Lund University, Department of Quaternary Geology,
Sölvegatan 13, S-223 62 Lund, Sweden
ABSTRACT
The Búði terminal moraine complex, southern
Iceland, was investigated with regard to glacial
stratigraphy and chronology. Thirteen new
radiocarbon dates of samples from southern Iceland
are discussed. They indicate that the Búði moraines
are of Preboreal age. The Búði moraines have hith-
erto been regarded as the type site for the Younger
Dryas glaciation in Iceland. Sediments from Alleröd
Interstadial have not been found in southern Ice-
land. This is believed to indicate a total glacial cov-
erage of the Southern Lowlands during the Younger
Dryas Stadial. The new radiocarbon dates are dis-
cussed in the light ofother recent data on the degla-
ciation in southwest-, west- and northeast Iceland,
all ofwhich indicate a much heavier Younger Dryas
glaciation than formerly assumed.
INTRODUCTION
The Búði moraine complex, which can be traced
across the lowlands of southem Iceland (Fig. 1), has
for long been considered to mark the terminal posi-
tion of a Younger Dryas ice advance in Iceland
(Kjartansson, 1943, 1958, 1961; Kjartansson et al.,
1964; Einarsson, 1964, 1968, 1978; Einarsson and
Albertsson, 1988). Originally, Kjartansson (1940,
1943) inferred a Younger Dryas age for the complex
by correlating it to the Raa moraines in Norway, the
central Swedish end-moraines and the Salpausselka
moraine complex in Finland, which are considered
to mark the main frontal positions of the Younger
Dryas ice sheet in Scandinavia (Andersen, 1979;
Berglund, 1979; Donner, 1978). Later, Einarsson
(1964) reported three shell samples from marine
sediments distally to the Búði moraines (Table I,
Fig. 1) as Preboreal in age, and concluded that the
moraines were of Younger Dryas age.
Recent investigations in SW- and W-Iceland
(Hjartarson, 1987; Ingólfsson, 1985, 1987; Ander-
sen et ai, in press) suggest that glaciers reached
beyond the present coast in the Faxaflói area
(Reykjavík and Borgarfjörður) after 11.000 BP. It
was suggested by Ingólfsson and Hjort (1988) that
the history of the deglaciation in Iceland as
described by Einarsson (1961, 1968, 1978) had to be
reevaluated. They pointed out the type site of the
Búði Stadial in southem Iceland as an important
locality to be investigated with regard to lithostra-
tigraphy and chronology of glacial events.
The first author of this paper has been working in
the Búði area for several years. During the
1982-1985 field seasons he found several new local-
ities with shell-bearing glaciomarine sediments near
the Búði moraines. He outlined the glacial stratigra-
phy presented below and collected samples for
radiocarbon dating. The second author worked in
the area during the 1988 field season, as a part of a
larger investigation on the deglaciation of Iceland,
and was engaged in the preparation and interpreta-
tion of the lithostratigraphical and chronological
JÖKULL, No. 38, 1988 1