Náttúrufræðingurinn - 2006, Side 41

Tímarit Hins íslenska náttúrufræðifélags
that separate Fagus friedrichii from Fagus
gussonii are more elliptic form of the lam-
ina, higher number of secondary veins
per 5 cm midvein, constant cra-
spedodromous venation and more
attenuate apex within the former species.
Fagus gussonii has more variety in form of
the lamina, fewer secondary veins per 5
cm midvein, craspedo- semicraspedo- or
pseudocraspedodromous venation and
an acute apex.
Pollen counts (3. and 4. table) from the
major sedimentary formations in North-
west and West Iceland indicate that
Fagus occupied the island during the
accumulation of sediments that are
15-13.5 Ma old and sediments that are
9-8 Ma old. When macrofossil data are
combined with the pollen data it is clear
that Fagus leaves, cupules, nuts and
pollen are only found in sediments
15-13.5 Ma in Þórishlíðarfjall in Selárdal-
ur, the Botn coalmine in Súgandafjörður
and in Mount Tafla at Ketilseyri, Dýra-
fjörður. After that no Fagus remains are
found in sediments until the 9-8 Ma oid
sediments at Hrútagil in Mókolisdalur,
where leaves, cupules, nuts and pollen
have been found (1. table).
Leaf specimens from the middle to
late Miocene of Iceland belong to two
morphospecies, Fagus friedrichii and
Fagus gussonii. Fagusfriedrichii appears to
belong to an ancient type of Fagus found
at high latitudes. Specimens from Iceland
and Alaska resemble the modem North
American Fagus grandifolia. Fagus
friedrichii from the 15 Ma Þórishlíðarfjall
and the Botn coalmine as well as the 13.5
Ma Mount Tafla exposure displays a dis-
junct distribution between Iceland and
Alaska. The plant-bearing sediments
from which it originates belong to the
two oldest sedimentary formations in
Iceland. In the following younger forma-
tions 12 Ma and 10 Ma Fagus is not
represented. Only in the younger 9-8 Ma
sedimentary formation at Hrútagil in
Mókollsdalur does Fagus reappear and
forms a major component of the flora.
The Fagus fossils in Hrútagil belong app-
arently to Fagus gussonii and both affini-
ties to coeval and modern species of
Fagus indicate that this late Miocene
Icelandic Fagus type colonised Iceland
from Eurasia. Is that the case or do we
have a new species that evolved parallel
to Fagus gussonii in Eurasia ?
Þakkir
Rannsóknamámssjóði er þakkað fyrir fjárhagslegan stuðning við Friðgeir
Grímsson, sem nú er í doktorsnámi í Háskóla íslands. Við viljum einnig
þakka Rannís sem styrkti þessa rannsókn. Margréti Hallsdóttur og Nátt-
úrufræðistofnun ísland er þakkað fyrir aðgang að steingervingum og
rannsóknaraðstöðu, m.a. til myndatöku. Þá viljum við þakka Michael A.
Akhmetiev, Walter L. Friedrich, Thomas Denk og samstarfsmönnum
hans, Ólöfu Emu Leifsdóttur, Jóni Eiríkssyni, Jóni Má Halldórssyni, Hall-
dóri Inga Jónssyni, Snorra Gíslasyni og Magnúsi Helga Jónssyni sem
hjálpuðu til við útivinnu í Selárdal, Botni og Töflu og á svæðinu kringum
Ketilseyri og í Mókollsdal undanfarin ár.
Heimildir
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2. Jóhannes Áskelsson 1946. Um gróðurmenjar í Þórishlíðarfjalli við
Selárdal. Andvari 71. 80-86.
3. Jóhannes Áskelsson 1957. Myndir úr jarðfræði íslands VI. Náttúru-
fræðingurinn 27. 22-29.
4. Friedrich, W.L., Leifur A. Símonarson & Heie, O.E. 1972. Steingerv-
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