USGS Open-File Report 94-588
Pliocene vegetation and climate in Arctic Russia
- Robert S. Thompson
- U.S. Geological Survey, Denver, CO
Tundra vegetation occurs today along the Russian Arctic coast under
extremely cold climates. During the early and middle Pliocene conditions
were quite different, and forests grew along the Arctic coast of Russia,
as well as in northernmost Alaska and Canada. Palynological and plant
macrofossil data from the Far Northeast of Russia indicate that Larix,
Picea, Pinus pumila, Alnaster, and tree-Betula lived near the coast.
Pollen spectra of this age contain only very low levels of Artemisia,
Chenopods, tundra herbs and other indicators of open vegetation (Giterman
et al., 1982; Fradkina, 1991). Forest cover decreased and Arctic
vegetation increased across northern Asia between approximately 3.5 Ma and
2.5 Ma (Fradkina, 1991; Volkova, 1991), suggesting pronounced cooling
occurred through this time. Shrub-Betula, Alnaster, moss, and Poaceae
increased in importance during this transition, as Larix, Picea, Pinus,
and other tree species declined. At the Krestovka section on the Kolyma
River in the Russian Far Northeast, Giterman et al. (1982) interpreted
palynological data as indicating a late Pliocene sequence of open forest
being replaced by treeless vegetation (steppe-tundra?), which in turn was
replaced by open larch forest. They also report ice-wedge pseudomorphs in
the late Pliocene sediments, indicating the initiation of permafrost.
Early Pleistocene sediments from this site contain a complex array of
permafrost features, suggesting increasingly cold conditions through the
Pliocene-Pleistocene transition.
References Cited:
- Giterman, R.E., Sher, A.V., and Matthews, J.V., Jr., 1982, Comparison of the development of tundra-steppe environments in west and east Beringia: pollen and macrofossil evidence from key sections. Pages 43-73, in Hopkins, D.M., Matthews, J.V., Jr., Schweger, C.E., and Young, S.B. (eds.), Paleoecology of Beringia: Academic Press, New York. 489 p.
- Fradkina, A.F., 1991, Pliocene climatic fluctuations in the Far North-East of the USSR, in Thompson, R.S., Borisova, O.K., and Svetlitskaya, T.V., Pliocene climates of the Northern Hemisphere: Abstracts of the joint US/USSR workshop on Pliocene paleoclimates, Moscow, USSR, April, 1990: U.S. Geological Survey Open-File Report 91-447, p. 22-23.
- Volkova, V.S., 1991, Pliocene Climate of West Siberia, in Thompson, R.S., Borisova, O.K., and Svetlitskaya, T.V., Pliocene climates of the Northern Hemisphere: Abstracts of the joint US/USSR workshop on Pliocene paleoclimates, Moscow, USSR, April, 1990: U.S. Geological Survey Open-File Report 91-447, p. 44-45.
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