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| Titel |
Arctic Late Cretaceous and Paleocene Plant Community Succession |
| VerfasserIn |
Alexei Herman, Robert Spicer, Robert Daly, David Jolley, Anders Ahlberg, Maria Moiseeva |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036825
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| Zusammenfassung |
| The Arctic abounds with Late Cretaceous and Paleocene plant fossils attesting to a thriving,
diverse, but now extinct polar ecosystem that sequestered vast amounts of carbon. Through
detailed examination of plant remains and their distributions in time and space with respect to
their entombing sedimentary facies, it has been possible to reconstruct changes in Arctic
vegetation composition and dynamics through the Late Cretaceous and into the Paleocene.
Based on over 10,000 leaf remains, fossil wood and palynomorph assemblages from
northeastern Russia and northern Alaska and palynological data from elsewhere in the
Arctic we identify a number of successional plant communities (SPCs) representing
seral development from early (pioneer), through middle to late SPCs and climax
vegetation. We recognise that (1) Equisetites and some ferns (typically Birisia, but
after the beginning of the Maastrichtian, Onoclea) were obligatory components of
the early SPCs; (2) first rare angiosperms (e.g. the dicot Vitiphyllum multifidum)
appeared in the middle SPCs of the Arctic in the Early – Middle Albian; (3) from late
Albian times onwards angiosperms became abundant in the middle SPCs of the
Arctic, but were still rare in the earlier and later SPCs; (4) monocots appeared in the
Maastrichtian early SPCs; (5) all Arctic Cretaceous late SPCs (and climax vegetation) were
dominated by conifers; (6) Arctic SPCs were more numerous and diverse under warm
climates than cold; (7) during the Albian and late Cretaceous, advanced (Cenophytic,
angiosperm-dominated) plant communities coexisted with those of a more relictual
(Mesophytic, dominated by ferns and gymnosperms) aspect, and plants composing these
communities did not mix; (8) coal-forming environments (mires) remained conifer,
fern and bryophyte dominated throughout the late Cretaceous and Paleocene with
little penetration of woody angiosperm components and thus are conservative and
predominantly Mesophytic in character; (9) bryophytes and ferns, with some subordinate
conifers, make up a persistent raised mire climax community that is most widely
developed in late Albian, Cenomanian and Campanian times, with the Campanian
exhibiting particularly high levels of bryophyte diversity; (10) general Cretaceous
SPC characteristics were maintained into the Paleocene due to migrations from
northeastern Russia into the more northerly northern Alaska and the lack of high levels of
extinction. The earliest Paleocene communities are, however, poorly understood as yet
and temporarily may have had a different character. These observations attest to
Arctic vegetation displaying persistent structure and dynamics despite a general
late Cretaceous cooling trend and events at the Cretaceous-Paleocene transition. |
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