Jökull - 01.12.1956, Blaðsíða 15

Fig. 12. Hólárjökull
1950. In the front to
tlie right the curved.
terminal moraine mar-
king the max. exten-
sion of the glacier
tongue in postglacial
time. Aerial photo S.
Thorarinsson 28 Aug.
1950.
a result of an advance of Kvíárjökull during
the first centuries of the Subatlantic Time. This
conclusion is supported, although not proved,
by the fact that a rhyolitic tephralayer hardly
more than ab. six thousand years old and
found in many soil profiles in Oræfi, was not
found in any of the profiles dug on Kvíármýrar-
kambur and Kambsmýrarkambur.
Summing up the results of the tephrochrono-
logical studies in Oræfi as regards the oscilla-
tions of the glaciers it has been established as
certain that both the Stóralda moraine and the
core of the moraines bordering Kvíárjökull are
prehistoric and as likely — although not yet
proved — that these moraines were formed dur-
ing the first centuries of Subatlantic Time as
a result of the climatic deterioration that began
ab. 600 B.C. The terminal moraine on the low-
land plain in front of Hólárjökull may be of
the same age. Consequently the climatic deter-
ioration during the first centuries of Subatlantic
Time has probably brought the glaciers in
question to the same or to a little more advanc-
ed position than they ever reached during the
last three centuries. It is still an open question
whether the thrust moraine in front of SW
Breidamerkurjökull mentioned earlier in this
paper, is prehistoric or not. Todtmann men-
tions (1952, p. 407) that she has not been able
to find the 1362 tephra on that moraine which
rather points to its formation being later than
1362. As to the terminal moraines in Stadar-
dalur, situated 5.5 km S of the present snout
of Sultartungujökull, I arn now — in light of
our present knowledge of the postglacial shore-
line movement in Iceland — of the opinion
that these moraines are older than the Post-
glacial Warm Period. By detailed studies of
tephralayers in the Stadardalur valley inside
these moraines it ought to possible to decide
whether this opinion is right or not. Ives and
King mention “greatly dissected and partially
buried remains of a moraine’’ in Morsárdalur ab.
5 km from the present snout of Morsárjökull.
They think it probable that these moraines are
of late glacial age marking the junction of
Skeiðarárjökull and Morsárjökull at that time
13