Jökull - 01.12.1990, Blaðsíða 80

Herbs and Graminids have frequencies about 40
%, suggesting an open character of the woodland, or
some mosaic of woodland, heath and most probably a
widespread peatland. The peatland seems to be reced-
ing, as may be inferred from the declining Cyperaceae
values. This suggests a drier and maybe a warmer
climate.
In the lake the three taxa, Myriophyllum alterniflo-
rum, Eu-Potamogeton and Isoetes echinospora, seem
to become stabilized. The green algae production is
at the level of about 1500 coenobia per cm2 per 14C-
year, which judging from Greenland data means that
the lake has become poor (Fredskild, 1983).
The sedimentation rate places this subzone at the
shift of the Early and the Middle Atlantic Chronozone.
COMPARISON WITH OTHER SITES IN
NORTH ICELAND
The present knowledge of the pollen stratigraphy
and vegetation history of North Iceland (e.g. Einars-
son 1985) is largely based on the pioneer work by
Einarsson (1961), where six pollen diagrams from peat
sections (at Torfalækur, Varmahlíð, Sólheimagerði and
Moldhaugar) were published. This was supported by
one radiocarbon date and tephrochronology, the lat-
ter making all stratigraphical correlation in Iceland
fairly easy. Two of these sections (Sólheimagerði and
Moldhaugar, Fig. 6) go farther back in time than the
tephra layer H5 dated at ca 6100 B.P. (Vilmundardóttir
and Kaldal, 1982). Of special interest for this study
are the three pollen diagrams from Moldhaugar show-
ing the first Betula maximum in Einarsson’s pollen
zone A, comparable with a part of the Local Pollen
Assemblage Zone KHM-2. Pollen zone A at Mold-
haugar predates the radiocarbon age of 7920±170*
B.P. (Heidelberg) (Einarsson, 1961). The age of the
upper zone boundary of KHM-2b, where the first Be-
tula maximum was reached in Krosshólsmýri, is esti-
mated 7850 B.P. Thus the general chronological trend
is in a fairly good agreement.
In Þórarinsson’s pollen diagram from Naustamýri,
farther south in Eyjafjörður (Fig. 6), one Betula max-
imum is seen below H5, this is assumed to represent
dwarf-birch heath (Þórarinsson, 1955).
Figure 6. Sites in North Iceland investigated by means
of pollen analysis. Torfalækur (peat, Einarsson, 1961);
Hafratjöm (gyttja, Vasari 1972; 1973, Vasari and
Vasari, 1990); Varmahlíð (peat, Einarsson, 1961);
Vatnskotsvatn (gyttja, Hallsdóttir, 1979); Sólheima-
gerði (peat, Einarsson, 1961); Ytri-Bægisá (peat,
Bartley, 1973); Moldhaugar (peat, Einarsson 1961);
Naustamýri (peat, Þórarinsson, 1955); Nykurtjöm
(gyttja, unpubl.); Krosshólsmýri; Héðinsvík (peat,
Straka, 1956). — Staðir á Norðurlandi, þar sem
frjógreind hafa verið lífrœn jarðlög (ýmist mór eða
vatnaset).
From Ytri-Bægisá Bartley (1973) published a
pollen diagram from a peat section spanning the last
8850 ± 120* (NPL-160) B.P. Chronologically the
deepest part of the peat section at Ytri-Bægisá cor-
responds to the upper part of the Krosshólsmýri sedi-
ment core dealt with here. Biostratigraphically these
two sections are fairly easy to compare, assuming YB-
1 with high values of Juniperus pollen to be equi valent
to KHM-2 and YB-2a corresponding to KHM-3. The
upper zone boundary of YB-2a is dated to 6840 ±95*
B.P. (Bartley, 1973).
Still farther west Vasari (1972; 1973) and Vasari
and Vasari, (1990) have published pollen and macro-
fossil diagrams from Hafratjöm (Fig. 6). Besides both
76 JÖKULL, No. 40, 1990