Jökull - 01.12.1989, Page 29

Accounts of the geology of Iceland do not mention
any major glaciers in SW Iceland during Younger
Dryas. However, the till on top of the marine sedi-
ments at Fossvogur and Skerjafjörður, shows beyond
doubt that the glaciers covered a much larger area of
Southwestern Iceland at this time than hitherto
thought.
the sediments at kópavogur bay
At the northem side of the Kópavogur bay, from
the head of the bay and a few hundred metres to the
west (Fig. 2), sediments similar to the Fossvogur
layers can be seen. The base of the sediments is not
exposed, but the lowermost part is a layered shell-
bearing siltstone, 2-4 m thick. A moraine of uncon-
solidated silt, sand and gravel rests on top of the lay-
ered sediment. It is most likely, that the siltstone is
of the same age as the Fossvogur layers, and that the
moraine was formed during Younger Dryas or Pre-
boreal, but no radiocarbon datings of these sedi-
ments have been performed. A few end moraines are
seen in this area. Some of them are shown on the
map of Tryggvason and Jónsson (1958). The inner-
most ones are near the football ground by the brook
Kópavogslækur, and another prominent end-
moraine is at the head of the bay. Here, the old
Kópavogur district assembly was held, and the
monument to mark the official tribute to the absolu-
tist monarchy AD 1662 stands on this moraine ridge
(Fig. 4). Low end-moraines are further west by
Kópavogur, these can be traced across the fjord to
Arnames. An additional end-moraine crosses Álfta-
nes between the Skógtjörn and Lambhúsatjörn inlets
(Fig. 2).
the álftanes end-moraine and the
ÁLFTANES STADIUM
The Álftanes end-moraine (Fig. 5) is the outer-
most moraine ridge that is undoubtedly visible in the
studied area. Einarsson (1968) assumes that it was
formed during the Older Dryas stadium. The age of
this stadium is 12,000-11,800 years BP. The Ice-
landic name for the Older Dryas is Álftanesstig,
named after the Álftanes end-moraine. This moraine
can be traced across the Álftanes peninsula past
Fig. 4. The end-moraine at the head of the Kópa-
vogur bay. Photo Á.Hj.
Mynd4. Jökulgarður við botn Kópavogs. Ljósm.
Á.Hj.
Bessastaðir and into the sea at Bessastaðanes (Fig.
2). Until recently, it was possible to see where it
reaches the shore on the outermost part of the Kárs-
nes peninsula in the town Kópavogur. The area is
now covered by dumped material.
The Álftanes end-moraine is more inland, both
geographically and according to glacial striae, than
the Fossvogur layers (Fig. 2). Moreover, it is clear
that it was never overridden by a glacier. The Álfta-
nes end-moraine must therefore be younger than the
Fossvogur layers, which date from the Alleröd Inter-
stadium according to the new radiocarbon datings
presented in this paper. It seems logical to assume
that the Álftanes end-moraine is from the Younger
Dryas or the Preboreal and that it belongs to the
group of end-moraines at the Kópavogur bay. It
does not, however, seem to mark the outermost stage
of the glacier of SW-Iceland during Younger Dryas.
The till in the topmost part of the Fossvogur layers
in Skerjafjörður shows that the glacier moved
further out. Péturss (1904) described two till layers
that lie conformably at the shore of Suðurnes, the tip
of the Seltjarnarnes peninsula. He concluded that
they represent the till layers at the top and bottom of
the Fossvogur layers. He explained the lack of the
JÖKULL, No. 39, 1989 27