| Abstract: | Eight global reconstructions are presented illustrating
the plate tectonic, paleogeographic, paleobathymetric
and paleoclimatic conditions during the Cretaceous.
These maps are based on global compilations of sea
floor spreading data, digital topography and bathymetry,
and lithologic and paleofloral indicators of climate. The
eight intervals represented include: early Maastrichtian,
Campanian, Turonian/Coniacian, Albian/Cenomanian,
early Albian, Barremian/Aptian, Hauterivian, and
Berriasian.
These reconstructions (see Figure 1) are a
visualization of 3D paleotopographic and
paleobathymetric models composed of over 6 million
pixel-points that capture digital elevation information at
a 10 x 10 km geographic resolution and 40 meter
vertical resolution. This quantitative, digital approach to
paleogeographic modeling permits new ways to
visualize and analyze the Earth's changing surface.
The process of building a 3D paleogeographic map
begins with the digital topography and bathymetry
compiled by NOAA (Smith & Sandwell, 2001), the
BEDMAP Project (British Antarctic Survey), and the
IBCAO Arctic Project (Jakobsson et al., 2000). The
topographic and bathymetric information is gridded at a
6-minute resolution, and the individual data points
(pixel-points) are rotated back to their paleo-positions
using the global plate tectonic model of the PALEOMAP
Project. The resulting map is reconstruction of
present-day bathymetry and topography in
paleo-coordinates.
In the next processing steps, the digital elevation and
bathymetric values are corrected to take into account
the complex effects of thermal subsidence (Stein &
Stein, 1992), glacial rebound, tectonic and volcanic
activity and erosion. The result is a revised, global
paleotopographic and paleobathymetric surface. To
complete the 3D paleogeographic model the new
topographic surface is digitally "flooded" by raising or
lowering sea level according to the estimates from
eustatic sea level curves (e.g., Haq et al., 1987).
In the final step, the pixels are color coded by elevation
and climate. The paleoclimatic assignments are made
on the basis of paleofloras (Willis and McElwain, 2002)
and a global database of lithologic indicators of climate
(Boucot et al., 2002). |