Náttúrufræðingurinn - 1988, Blaðsíða 26

northeast flowing ice streams from the ice
streams and outlet glaciers which flowed
through passes and along the valleys and
fjords east of the ice divide. All the area
was ice-covered except the high moun-
tains between the outlet glaciers. These
mountains held cirque glaciers and minor
valley glaciers at that time. North and
south of these a few nunataks were close
to the secondary ice divide.
Breiödalur stage, the middle stage is
represented by moraines in the area be-
tween Lón and Norðfjöröur, which means
that the edge of the main Icelandic ice
sheet had retreated to the present coast
line of East and Southeast Iceland. The
lowering of the relative sea-Ievel by 12 m
in Norðfjörður, Reyðarfjörður and Fá-
skrúðsfjörður was contemporaneous with
the retreat from the Fáskrúðsfjörður mo-
raines. Due to differences in the isostatic
lowering of the land the absolute altitude
of the shorelines is greater in the inner
parts of the fjords than in their outer
parts. The altitude of the marine limits im-
mediately outside the Breiðdalur mo-
raines is between 39 m a.s.l. in Stöðvar-
fjörður and 59 m a.s.l. in Reyðarfjörður.
This difference in the altitude of the mar-
ine limits is explained by the different ex-
tent and thickness of the outlet glaciers.
The Breiðdalur moraines were formed ei-
ther during a standstill of the ice fronts or
a readvance. The extent of ice-free areas
in east and Southeast Iceland was greatly
increased in the time between the forma-
tion of the Fáskrúðsfjörður and Breiðdal-
ur moraines. The high mountains between
the fjords still held cirque and valley gla-
ciers.
A third set of moraines is found behind
the Breiðdalur moraines in Reyðarfjörð-
ur, Fáskrúðsfjörður, Breiðdalur and Beru-
fjörður. When the glaciers retreated from
the Breiðdalur moraines sea-level regres-
sed, but was stabilized again between 8 m
and 19 m below the previous marine limit
at the moraines in Lón, Alftafjörður, Ha-
marsfjörður, Berufjörður, Breiðdalur,
Stöðvarfjörður, Fáskrúðsfjörður, Reyðar-
fjörður and Eskifjörður. This third set of
moraines and lower marine limits together
constitute the Berufjörður stage, the
youngest stage in the deglaciation and sea-
level changes in East and Southeast Ice-
land. When the glaciers retreated from
the Berufjörður moraines sea-level regres-
sed towards present sea-level.
The stratigraphical position of the Fá-
skrúðsfjörður, Breiðdalur and Berufjörð-
ur moraines and their related marine lim-
its is uncertain, as radiometric dates are
still lacking. The above described course
of deglaciation and sea-level changes in
East and Southeast Iceland is correlated
to the Late Weichselian Substage. A com-
parative pattern of deglaciation and sea-
level changes is known from South and
West Iceland. A tentative correlation be-
tween these two regions in Iceland en-
ables following conclusions to be drawn.
The formation of the Fáskrúðsfjörður
moraines concurred with the glacier read-
vance during the Álftanes Stadial, 12,000-
12,300 l4C years B.P. The Breiðdalur mo-
raines were formed concurrently with the
glacier readvance in the early Búði Sta-
dial, about 11,000 I4C years B.P. The
Berufjörður moraines may have been
formed in Early Flandrian time, 9000-
10,000 14C years B.P. It is, however,
equally possible that the Berufjörður mo-
raines reflect the twofoldness of the
Younger Dryas Stadial as it is described in
the Oslofjord area and Southern Sweden
and were, therefore, formed about 10,500
14C years B.P.
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