Jökull - 01.12.1978, Page 4

These channels show that the surface of the
tributary glacier was lower than the surface of
the Austurdalur glacier.
The main ice stream was an outlet glacier
from the main ice sheet which covered a major
part of the country during the last glaciation.
This outlet glacier was much more active than
the local tributary glaciers due to the fact that
the northern part of Iceland was in a rain
shadow on the leeward side of the ice sheet
(Th. Einarsson 1968, Kjartansson 1955).
Striations show that the main ice stream
was along Vesturdalur into the Skagafjördur
valley. On Ellidi, the summit between
Austurdalur and Vesturdalur valleys, the
glacial striations are parallel to the direction
of Vesturdalur. This indicates that the
Vesturdalur glacier was thicker than the
Austurdalur glacier. On the mountains bet-
ween the Vesturdalur and Svartárdalur val-
leys, the striations are parallel to Vesturdalur.
At the mouth of Mælifellsdalur (a western
tributary valley to Skagafjördur) the striae
show that the glacier in the main valley
diverged into the mouth of this tributary val-
ley.
MEDIAL MORAINES
The glaciation pattern demonstrated by the
glacial striation and drumlins is further illus-
trated by remnants of medial moraines (Fig.
1). They are found in several places either in
the form of esker complexes or as mounded
ablation moraines. These remnants lie on the
lee side of mountains and are elongated in the
direction of the glacier flow.
Vatnsskard — Sæmundarhlíd
A medial moraine was deposited on the lee
side of Háafell on the southern side of Vatns-
skard (Fig. 3). A great deal of the ice contact
sediments is in the form of eskers and esker
complexes. However, some of the sediments
are covered by ablation till. To the south of
the medial moraine considerable marks of
meltwater erosion are found. Lateral channels
in Háafell and other meltwater channels (for
example in Vídimýrardalur and Valadalur)
show that lateral meltwater flowed along the
western margin of the Skagafjördur outlet
glacier.
The fluvioglacial sediments in this area can
be divided into three main groups according
to their morphology. In the area between the
farmstead Fjall in the north and the main
road in the south, the fluvioglacial sediments
are divided into two branches. The western
one has been subject to a considerable fluvial
erosion after the ice melted away, resulting in
disappearance of ice contact features. The
eastern branch, however, consists of eskers
which form a well-developed anastomosing
system. This indicates a supraglacial origin. —
To the north of the farmstead Fjall the
anastomosing esker system transforms into a
kame terrace. The terrace contact inclines
northwards by 15—20 m/km. The eastern
part of the terrace is dissected by kettles,
kames and eskers. Some of the eskers descend
downhill from the terrace and are of the type
which Mannerfelt (1945) called “slukásar”.
North of this kame terrace, the sediments form
some large eskers which meander downstream
(Fig. 4). No ablation till has been found on
these eskers, but their form indicates sub-
glacial or englacial rather than supraglacial
formation.
The fluvioglacial deposits in the Sæmund-
arhlíd-Vatnsskard area are interpreted as
remnants of a medial moraine, which ex-
tended from the Háafell mountain to the
kame terrace in Sæmundarhlíd. Thus the
kame terrace is a remnant of a lateral moraine.
The sediments were protected from the main
meltwater streams in the Skagafjördur valley
by the ridge Langholt. Only the highest lying
lateral channels in Háafell have diverted
meltwater to the area in question. (Fig. 3).
When the ice surface had subsided to
approximately 200—250 m altitude the melt-
water flow along the ice margin was diverted
to the eastern side of Langholt and only a
small quantity of water, mostly from Vatns-
skard, still flowed where the ice contact
sediments are located.
2 JÖKULL 28. ÁR