Náttúrufræðingurinn - 2006, Síða 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
1. Guðmundur G. Bárðarson 1918. Um surtarbrand. Andvari 43. 1-71.
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-
ingar í millilögum í Mókollsdal. Náttúrufræðingurinn 42. 4-17.
5. Akhmetiev, M.A., Bratzeva, G.M., Giterman, R.E., Golubeva, L.V. &
Moiseyeva, A. I. 1978. Stratigrafiya i flora pozdnego Kainozoa Is-
landii [Late Cenozoic stratigraphy and flora of Iceland]. Trudy
Geologischeskogo Instituta, Academia Nauk SSSR 316. 1-188
(á rússnesku).
6. Denk, T. 1999. The taxonomy of Fagus in western Eurasia and the
ancestors of Fagus sylvatica s.l. Acta Palaeobotanica Supplement 2.
633-641
7. Leifur A. Símonarson, Akhmetiev, M.A, Ólöf E. Leifsdóttir, Friedrich,
W.L. & Jón Eiríksson 2000. Rannsóknir á tertíerflóru í Dýrafirði.
Ágrip erinda og veggspjalda.Vorráðstefna Jarðfræðifélag íslands.
31-33.
8. Leifur A. Símonarson, Akhmetiev, M.A, Ólöf E. Leifsdóttir, Friedrich,
W.L. & Jón Eiríksson 2002. The Upper Miocene Dufansdalur-Ketils-
eyri plant-bearing horizon in Northwest Iceland. Abstracts the 25th
Nordic Geologic Winter Meeting Reykjavík. 189.
9. Friðgeir Grímsson & Denk, T. 2005. Fagus from the Miocene of
Iceland: systematics and biogeographical considerations. Review of
Palaeobotany & Palynology 134. 27-54.
10. Moorbath, S., Haraldur Sigurðsson & Goodwin, R. 1968. K-Ar ages
of the oldest exposed rocks in Iceland. Earth and Planetary Science
Letters 4.197-205.
11. McDougall, I., Leó Kristjánsson & Kristján Sæmundsson 1984.
Magnetostratigraphy and geochronology of northwest Iceland.
Journal of Geophysical Research 89, B8. 7029-7060.
12. Bjöm S. Hardarson, Fitton, J.G., Ellam, R.M. & Pringle, M.S. 1997. Rift
relocation - a geochemical and geochronological investigation of a
palaeo-rift in northwest Iceland. Earth and Planetary Science Letters
153.181-196.
13. Heer, O. 1868. Die Fossile Flora der Polarlánder enthaltend die in
Nordgrönland, auf der Melville-Insel, im Banksland, am Mackenzie,
in Island und in Spitzbergen entdeckten fossilen Pflanzen. Flora
fossilis arctica 1. Schulthess, Zúrich. 1-192.
14. Friedrich, W.L. 1966. Zur Geologie von Brjánslaekur (Nordwest-
Island) unter besonderer Berúcksichtigung der fossilen Flora. Sond-
erveröffentlichungen des Geologischen Institutes der Universitát
Köln 10.1-108.
15. Haukur Jóhannesson 1980. Jarðlagaskipan og þróun rekbelta á
Vesturlandi. Náttúrufræðingurinn 50. 13-31.
16. Sveinn Jakobsson 1968. Geologiske iagttagelser fra Selárdalur, Arnar-
fjördur, Island. Óbirt skýrsla. 1-8.
17. Leó Kristjánsson, Björn S. Harðarson & Haraldur Auðunsson 2003. A
detailed palaeomagnetic study of the oldest (approximate to 15 Myr)
lava sequences in Northwest Iceland. Geophysical Journal
Intemational 155. 991-1005.
18. Dilcher, D.L. 1974. Approaches to the identification of angiosperm
leaf remains. Botanical Review 40.1-157.
19. Denk, T. 2003. Phylogeny of Fagus L. (Fagaceae) based on
morphological data. Plant Systematics and Evolution 240. 55-81.
20. Heer, O. 1869b. Flora fossilis Alaskana. Kongliga Svenska Veten-
skaps-Akademiens Handlingar 8 (4). 1-41.
21. Jóhannes Áskelsson 1956. Myndir úr jarðfræði íslands IV. Fáeinar
plöntur úr surtarbrandslögunum. Náttúrufræðingurinn 26. 44-48.
22. Unger, F. 1847. Chloris protogaea. Beitráge zur Flora der Vorwelt.
Wilhelm Engelmann, Leipzig. 150 bls.
23. Denk, T. & Meller, B. 2001. The systematic significance of the
cupule/nut complex in living and fossil Fagus. International Journal
of Plant Sciences 162. 869-897.
24. Greuter, W. (ritstj.) 2000. International Code of Botanical Nomen
clature (Saint Louis Code) adopted by the Sixteenth International
Botanical Congress St. Louis, Missouri, July-August 1999. Koeltz
Scientific Books, Königstein. 474 bls.
25. Heer, O. 1858. Fagus antipofii. í: Abich, W. H.: Beitráge zur
Paláontologie des asiatischen Russland. Mémoires de L'Académie
Impériale des Sciences de St.-Pétersbourg, 6 (7). Bls. 572.
26. Zhilin, S.G. 1974. The Tertiary floras of the Plateau Ustjurt
(Transcaspia) (in Russian). Komorov Botanical Institute of the
Academy of Sciences of the USSR, Leningrad. 122 bls. (á rússnesku).
27. Denk, T. 2004. Revision of Fagus from the Cenozoic of Europe and
southwestern Asia and its phylogenetic implications. Documenta
naturae 150. 1-72.
28. Iljinskaja, I.A. 1982. Fagus L. í: Takhtajan, A.L. (ritstj.) Magnoliophyta
Fossilia SSSR 2, 64. Volume 2. Ulmaceae to Betulaceae. Institutum
101