If a mere picture is worth a thousand
words, a suite of 3-D images is perhaps comparable to encyclopedic
in the value of the message it conveys.
It takes only a few choice words, however, to characterize
the visual impact of certain 3-D images, with "stunning" and "spectacular"
often at the top of the list.
Such was the case with the graphics accompanying
the presentation "Evolution of the Northern Gulf of Mexico Through
the Cenozoic -- A 3-D Visualization Tour," given at the interactive
e-poster session at the AAPG Annual Meeting last month in Salt Lake
The array of vibrant images was proffered by Bill
Galloway during his delivery of the paper, which was co-authored
by Dennis A. Sylvia and R. Combellas. The trio is based at the Institute
for Geophysics, University of Texas at Austin.
Probably the most dramatic 3-D aspect of the presentation
was a series of surfaces that basically reflect a quantitative paleobathymetry
of the subject region, which was contoured as a derivative of the
standard paleontologic-base depth zonation.
"It was with a fair bit of effort that this was converted
into an actual pseudo-bathymetric map," Galloway noted.
The material he presented at the e-poster gathering
was an outgrowth of an industry consortium called the Gulf Basin
Depositional Synthesis project, which originated seven years ago.
"During the first two phases of the project, we created
a digital GIS database and used this to create suites of maps, primarily
for our supporting companies," Galloway said. "But Phase 3, which
ended six months ago, was different.
"We added new kinds of information," he said, "essentially
creating a GIS database and synthesizing and consolidating interpretations
for the Tertiary history for the whole Gulf basin -- with emphasis
on the U.S. half of the Basin -- for the whole Cenozoic.
"One of the additions during Phase 3 was the compilation
of paleobathymetric data, which were derived from micro-paleo reports
collected over the years of OCS drilling.
"We hit on the idea of going beyond just creating
a little quilt that used numerical zones from shallow to deep water,
which usually means I to VI," Galloway said, "to attempting to convert
this to actual depths.
"It was not easy."
'Some Interesting Things'
To accomplish this goal, Sylvia called on expertise
he acquired as a meteorologist with the U.S. Air Force.
"Dennis was aware of the use of map algebra, which
meteorologists do regularly with such things as pressure," Galloway
said. "He did a lot of conditioning in the sense of establishing
boundaries, e.g., shoreline locations, maximum depths for a paleo
GOM, so we could put boundaries on the basin."
"We extracted in a selective way the paleobathymetry
information for each stratigraphic unit that the database differentiated
from a very large database released by the MMS," Galloway noted,
"which includes paleo reports from more than 10,000 wells in the
Paleobathymetric surfaces were constructed for 13
time steps during the Cenozoic. The reconstructions show how 3-D
visualization can be used to evaluate the impact of events such
as continental climate change and tectonics on the sedimentation
history of the Gulf basin.
Bathymetric surfaces were modeled for each of the
major Oligocene and younger depositional episodes. Doppler maps
were also constructed depicting depositional pattern change.
"Geologically, you see some interesting things going
on, and some surprising things are highlighted when you look at
the map as a 3-D rather than just color blotches," Galloway said.
"And likewise, when you subtract and look at a map
that shows change through time rather than a condition that exists
at a particular interval of time."