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Figure 4
a) Striated dropstone from Eocene sediments of the ODP 913B core.
b) Quartz grain exhibiting surface features (e.g. conchoidal fractures) resulting from abrasion in continental ice.
c) Electron micrographs of warm indicator Eocene pollen grains extracted from ODP 913B samples.
long-term cooling of ~3–5 °C starting near the EOB
(Schouten et al., 2008). We have now corroborated this
evidence by employing another set of proxy data derived
from the well preserved spore and pollen assemblages
extracted from samples from Site 913B. These terrestrially
derived microfossils have permitted the determination of
the first high northern latitude terrestrial climate estimates
for the Eocene to Oligocene interval (Eldrett et al., 2009),
including mean annual precipitation and temperature
estimates. By comparing the known climatic tolerances
of the fossil forms with their nearest living relatives, a
method known as Bioclimatic Analysis has indicated that
the most striking temperature variation is represented not
in mean annual or warm monthly mean temperatures,
but in the cold-month (winter) mean temperatures, which
demonstrate a cooling of ~5-6 ºC down to values of
0–2 ºC across the EOB. This therefore indicates increased
seasonality set in before the Oi-1 event and serves to
demonstrate that the stable oxygen isotope shift across the
EOB records both a temperature decrease and a build-up of
ice. However, the relatively warm summer temperatures at
that time mean that continental ice on East Greenland was
probably restricted to alpine outlet glaciers (Eldrett et al.,
2009, Weijers et al., 2007a).
Conclusions
The new palaeoclimate records described above have
radically improved our understanding of the dramatic
environmental changes that occurred through the Arctic
Palaeogene. By illustrating some of the climatic variability
34 Teaching Earth Sciences Vol 35 No 1 2010 www.esta-uk.net