Jökull - 01.12.1984, Blaðsíða 127

than having been sculptured by a substantial ice
cap.
Models for the Late Weichselian
in the Borgarfjördur region
Apart from Bárdarson s (1923) interpretation
of the Late Weichselian environments in the
Borgarfjördur region, three basically different
models have been presented.
Th. Einarsson (1960, 1961, 1963, 1967, 1968,
1973) suggested that the Borgarfjördur region
became ice-free at about 13,000 BP. The sea
followed the retreating glaciers and marine sedi-
ments were accumulated. A glacial readvance
during the Álftanes (Older Dryas) stage, starting
at about 12,300 BP formed terminal moraines in
the entrances of the Borgarfjördur tributary val-
leys. A glacier advancing from the east, from the
Svínadalur-Hvalfjördur area, piled up conspi-
cuous terminal moraines across the Leirársveit
lowland (the ridge Skorholtsmelar). According to
Th. Einarsson the Borgarfjördur main valley was
not glaciated during this phase. About 12,000 BP
the glaciers retreated and the sea transgressed to
the marine limit. According to Th. Einarsson the
region was not seriously affected by the Búdi
(Younger Dryas) glacial readvance. Th. Einars-
son’s interpretation concurs substantially with
that of Bárdarson (1923) and is supported by the
work of Jónsson (1972), Gunnlaugsson et al.
(1973), Torfason (1974) and Ingólfsson (1981).
Ashwell (1975) presented a model in which,
prior to about 12,500 BP, the entire landscape,
except the highest points of Skardsheidi, was
covered by ice moving from NNE across ridges
and valleys towards the present edge of the Ice-
land shelf. Accompanied by the thinning of the
ice in the millennia before 12,500 BP the con-
tinuous ice broke into separate ice streams in the
mountainous areas. These ice streams converged
on the Borgarfjördur Iowlands and formed a
piedmont-glacier which possibly extended
towards the SW and around the southern end of
Hafnarfjall onto the Melasveit lowlands. With
rising sea level the glacier floated, resulting in a
short lived ice-shelf which deposited material on
the bottom of the sea and contorted the bottom
sediments. Ashwell emphasized the importance
of subglacial and englacial water activity in the
deglaciation process. He does not recognize any
glacial readvances, but seems to consider the
deglaciation to have been more or less con-
tinuous.
Sigbjarnarson (1976, 1980) outlined a model
for the Late Weichselian in the region by which
the movement of the glaciers was mainly directed
through the valleys of Borgarfjördur from a gla-
cial centre north of the present Langjökull gla-
cier. As the glaciers retreated the centre shifted
to the eastern part of the Snæfellsnes peninsula.
Sigbjarnarson proposed two successive glacial
readvances in the Borgarfjördur region which
reached the Melasveit area. He suggested that
the ridge Skorholtsmelar is a terminal moraine
deposited during these readvances. According to
Sigbjarnarson, both the glacial readvances occur-
red during periods of relatively high sea level.
The former glacial readvance, which Sigbjarnar-
son correlated with the Older Dryas, occurred
when the sea level stood some 100-110 m above
the present sea level. The latter glacial readv-
ance, which Sigbjarnarson correlated with the
Younger Dryas, occurred when the sea level was
60 m above the present sea level. Sigbjarnarson
suggested that the tributary valleys of
Borgarfjördur were ice-free during the last stages
of deglaciation. He further suggested the possibil-
ity that they were occupied by ice-dammed lakes.
Sæmundsson and Einarsson (1980) mapped the
ridge Skorholtsmelar as a terminal moraine
formed in front of giacier which moved down
Borgarfjördur, thereby agreeing with Sigbjarnar-
son’s interpretation.
Little ice age glacier growth in Skardsheidi
When reviewing studies of the Late Weichse-
lian in the Borgarfjördur region, it can be of
interest to note that during the Little ice age
glaciers grew considerably in the north-facing
wall of Skardsheidi. Possibly it can throw some
light on the Late Weichselian environment and
climate.
Ólafsson (1772) noted a small cirque-glacier in
the north-facing wall of Skardsheidi, above the
entrance to the Skorradalur valley. He inter-
viewed the local farmers about the glacier, and
concluded that it had begun to grow during the
first decades of the 18th century. The Icelandic
naturalist Sveinn Pálsson visited the area in late
August 1791 and commented on the greenish
colour of the glacier ice and its crevassed surface
(Pálsson 1945). Kjerulf {1853) noticed the glacier
JÖKULL 34. ÁR 125