Terrestrial Palaeoecology and Global Change

Chapter 7. Climate change
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and tall trees (Mastixia of montane rainforests), the fruit–seed remains prevail over leaf
remains, a taphonomy indicating shrubland rather than rainforest.
At the same time, the mammalian turnover, with a modification of the crown types in
the larger herbivores over the PEB (Janis, 2000; Bowen et a., 2992), indicates a change
to a more open Eocene vegetation. According to a recent palynological analysis by
Harrington (2001), the vegetation change was insignificant, with the Early Eocene communities
slightly more diverse and “more successional”. However, a drop of Tricolpites,
a dominant palynotype of the Palaeocene nemoral biome, and a rise of palms as well as
herbaceous monocots that increased by about 80% indicate a change to more open
vegetation. The carbonate rhizocretions of thick red palaeosols indicate a seasonality of
precipitation. In the Bighorn Basin, Wyoming (Fig. 101) the reworked palaeosols contain
silicified conifer wood. A subtropical climate with pronounced seasonal draughts is inferred
also for the Sparnacian of Central Europe on the basis of oxygen and strontium
isotope records (Schmiz & Andereasson, 2001). The palynological, taphonomic and sedimentological
data are thus complementary in suggesting a major deforestation event.
In a broader phytogeographic context, the anomalous advance of thermophilic vegetation
to high latitudes is a regional trans-Atlantic, rather than global, phenomenon. Chro-
Fig. 101. Redbed sequence over the Palaeocene–
Eocene boundary, Bighorn Basin, Wyoming
(photograph taken during field trip of the
International Conference on “Climate and Biota
of the Early Paleocene”, Powell, 2001).