Biology Reference
In-Depth Information
5
Early On
Middle Cretaceous through the Early Eocene
The use of contextual information to approach ecosystem history
establishes several expectations about New World environments
and vegetation at 100 Ma. These expectations are particularly
valuable when direct paleontological information is meager or
scattered geographically and stratigraphically, and when the age
of the assemblage precludes assuming taxonomic or ecological
equilivancy with modern forms. A hundred million years ago,
landscapes were low-lying and sea levels were higher by up to
300 m (by plus of 100 m according to Miller et al. 2005), result-
ing in the widespread fl ooding of coastlines and interior lowlands
(fi g. 2.10). Habitats included coastal margins and deltas, stream
channels, levees, swamps, marshes, lakes and lake margins, slopes,
and moderately elevated uplands. High sea levels also contributed
to extensive maritime climates, which are characterized by muted
seasonal variations.
Atmospheric CO
2
concentration is estimated to have been at
least 1620 ppmv, or 4-6 times the present 380 ppmv (Beerling
