Jökull - 01.12.1990, Blaðsíða 38

700-800 m high peninsula between Dýrafjörður and
Önundarfjörður (Fig. 4) was reached by Sigurvinsson
(1982,1983).
The approximately 100 km long and 20-30 m high
submarine ridge at the edge of the shelf 130 km west
of Breiðafjörður may represent the Weichselian max-
imum glacier extent about 18,000 B.P. (Ólafsdóttir,
1975). Sigurvinsson (1982) pointed out that a 750 m
thick glacier at the mouth of Dýrafjörður and Önund-
arfjörður with a parabolic surface profile, would have
terminated only 25-30 km offshore, i.e. 70-80 km
inside the edge of the shelf. It has, furthermore, been
suggested by Hjort et al. (1985) that during the We-
ichselian maximum glaciation the glaciers on Hom-
strandir could not have extended more than 6-10 km
beyond the present coastline. At the entrance to Aðal-
vík a concentric zone of shallow banks running south-
westwards from Straumnes to a position about 4 km
northwest of Ritur (Fig. 4) may represent the true We-
ichselian maximum position of the glacier margin out-
side Aðalvík (Hjort et al., 1985).
During the deglaciation of Homstrandir, relative
sea-level stood at the marine limit at about 25 m a.s.l.
when the general retreat of the glaciers was interrupted
by a readvance. A Younger Dryas age has been in-
ferred for the advance and thus for the marine limit on
Homstrandir (Hjort et al., 1985). In the area south of
ísafjarðardjúp the marine limit is found at somewhat
different altitudes. It lies at 40-50 m a.s.l. at Ingjalds-
sandur in Önundarfjörður (Sigurvinsson, 1982), and
according to Lárusson (1977) it reaches as high as 110
m a.s.l. in Dýrafjörður and 85 m a.s.l. in Amarfjörður
(Fig. 4). Kjartansson (1968) shows the marine limit at
80 m a.s.l. near Gilsfjörður on the south coast of the
Vestfirðir peninsula, and at 70 m a.s.l. on Gjögur on
the east coast of the peninsula. The age of the marine
limits is still unknown.
Two redeposited tephra layers have been found
in Northwest Iceland (Fig. 4), the rhyolitic Skaga-
fjall Tephra in glaciolacustrine sediments in Dýra-
fjörður (Sigurvinsson, 1983) and the basaltic Hæla-
vík Tephra in glaciomarine sediments on Homstrandir
(Hjort et al., 1985). The Hælavík Tephra has been
correlated with the Saksunarvatn Ash in the Faroe Is-
lands (Kvamme, 1988), which in turn has been 14C
Figure 5. Late Weichselian and early Holocene
end-moraines and marine-limit features in West
Iceland. Legend: 1) 14C dates. 2) Raised
beaches. A) End-moraines from the Skipanes
event. C) End-moraines from the Skorholtsmelar
event. — Jökulgarðar og sjávarborðsmenjar frá
síðjökultíma og upphafi nútíma á Vesturlandi. Tákn:
1) Geislakolsaldursákvarðanir. 2) Forn fjörumörk.
A) Jökulgarðar Skipanessstigs. C) Jökulgarðar
Skorholtsmelastigs.
dated to 9,000-9,100 B.P. (Mangerud et al., 1986).
This date postdates both the glacier readvance and the
marine limit on Hornstrandir.
WEST ICELAND
Ingólfsson (1984, 1985, 1987, 1988) studied the
glacial development of the lower Borgarfjörður re-
gion in West Iceland (Fig. 5) with regard to mor-
phology, lithostratigraphy and chronology of glacial
events. The chronological studies were supported with
a total of about 25 14C dates.
In Bolling time the lower Borgarfjörður area was
ice-free but submerged as relative sea-level stood
above the 60 m level at about 12,300 B.P. in the north-
ernmost part of the investigation area. This is referred
to as the Ásbakkar event, which has been 14C dated
between 12,505 ± 110 B.P (Lu-2195) and 11,885
± 100 B.P. (Lu-2374) (Ingólfsson, 1988). Around
12,000 B.P. a glacier from Borgarfjörðuradvanced and
reached Skipanes in the southem part of the investiga-
tion area. At the same time a glacier from Hvalfjörður
36 JÖKULL, No. 40, 1990