| Abstract: | The Maastrichtian (Late Cretaceous) is a stage
better known for its abrupt, enigmatic end, rather than
for any inherent interest. Yet the K-T extinction event
and its consequences, can only be understood in the
context of the contemporary climate and environment.
The Maastrichtian is a time of global cooling, but with
no persuasive evidence of large-scale polar glaciation.
Seaways, though beginning to close, continued to
dominate the paleogeography of North America,
Eurasia, South America and North Africa. The Arctic
was almost fully land-locked, whilst in Asia highlands
extended from Indonesia north through China and into
NE Russia. The Maastrichtian is a stage with a large
terrestrial and marine geological record on all
continents and is present at a significant number of
DSDP and ODP sites. Terrestrial fossil localities, with
many recognizably modern forms, extend from the
Antarctic Peninsular to Alaska and throughout the
continental interiors of North America and Asia. As
such the Maastrichtian provides an ideal time interval
for which to model the climate and evaluate the
results.
A series of atmosphere (AGCM) and coupled
ocean-atmosphere (AOGCM) model experiments have
been run using the latest Hadley Centre model,
HadCM3. The details of this model, boundary
conditions, the climate and ocean results are
described in a separate presentation in this workshop
(Valdes). Here is presented a quantitative and
qualitative evaluation of the "veracity" of the experiments
using a comprehensive dataset of geological climate
proxies. These include fossil vertebrates, megafloras,
paleosols, and stable isotope geochemistry.
Preliminary assessment indicates that the AOGCM
experiment better replicates "observations" than
existing AGCM experiments.
While such data-model comparisons increase our
understanding of model behaviour, the integration of
data with carefully designed model experiments can be
also used to address other geological problems. This
is only possible because of the compilation of a
comprehensive dataset of geological, tectonic and
paleontological information, and the construction of a
detailed, "hydrologically-correct," global paleo-
topographic and -bathymetric digital elevation model
(DEM). This DEM not only supplies an essential
boundary condition for the modelling experiments, but
also provides the context for investigating and further
understanding processes on the surface of the
Maastrichtian Earth, including the distribution and
evolution of life. |