The Power of a Word

The Power of a Word
By Steve Earle Editor
One of the good things about the editor position is the exposure you get to new geologic thinking. We reviewed some
interesting abstracts for this month which I encourage you to read.
For Martin Cassidy’s Northsiders talk on the distribution of CO2, he mentions areas of tectonic escape. Not being familiar with the term, I quizzed Martin and he provided this quote from his coauthor, Kevin Burke: "Because buoyant continental
or arc material generally moves during collision towards a nearby oceanic margin where less buoyant lithosphere crops out, we call the process of major strike-slip dominated motion toward a ''free-face'' (to be) tectonic escape." The plate boundary
interactions here provide a conduit to the mantle and the gases located there.
Another moment occurs at the end of Jon Blickwede’s abstract for the General Dinner Meeting where he mentions an Upper Jurassic erg. Being a bit fuzzy on this term, I looked it up and came up with this definition: “In a desert region, an area with a large accumulation of sand, generally in the bottom of a huge basin in which a former river piled up alluvium. Ergs are areas of actively shifting dunes, fossilized dunes, or extensive sand sheets.” The Sahara Desert is the type locale for an erg. The Norphlet sands are interpreted as dune deposits. A paleogeographic map for Upper Jurassic time shows the Hispanic Corridor along the southern border of the North American craton, about where Louisiana to the Florida panhandle are located, as part of the proto-Atlantic which was continuing to open up. On the Pacific side we find the Entrada sands; these paleo-dunes sit above the Navajo, probably the thickest erg deposit in North America. It takes but a little stretch to realize that a substantial volume of sands, sourced from the North American craton, was blown southward and deposited along the edge of the fringing oceans. There is actually still a lot of “white space,” the term used by Robin Hamilton last month in his “Identifying New Hydrocarbon Plays” talk, meaning that there are plenty of areas where potential Norphlet equivalent sand dunes could be hiding. All this from a little 3-letter word, but a word is just shorthand for an idea and the power of an idea can be tremendous.
This month we host another talk on global climate change, a topic that has engendered a fair amount of discussion.
The HGS has not taken a position on this issue, nor do we see any compelling reason to do so. If you polled
the members, you would get the full spectrum of opinion from “man has little to no effect on global climate” to “man is changing
the atmosphere and will be directly responsible for profound and serious changes to our environment.” Most of us probably fall in between these end members, although I am closer to the later statement. Following the AAPG forum was interesting with a lot of well-considered arguments and the occasional statement that suggests people should only talk on topics they know something about. I will try to talk about something I know.
As an explorationist, I have spent some time working with models. Two things you learn about models is that there are lots of
assumptions and they are rarely, if ever, unique. However, they can offer valuable insights when studying complex systems.
Atmospheric physicists have been improving their understanding and hence their models of global climate. They have come a long ways from the crude description they started with. I believe there is at least one critical component that is still poorly understood, but they have been able to make useful predictions that test their models in the short-term and the results appear to confirm anthropomorphic impact which will accelerate the long-period warming trend which we have no control over. However, the science is still evolving so I suggest you stay tuned.
My “words of wisdom” this month came from my freshman physics professor who told his assembled students:
Remember, all science is a lie. As scientists, we can aspire only to a better and closer approximation of
the truth.
The North American and International Explorationists groups have teamed up to bring you “Wilcox Night” on October 29 with
two papers on the deepwater Wilcox sands and, more specifically, the Jack discovery. There are two different interpretations for the depositional setting of this important new sand unit. Chevron’s interpretation is provided in their abstracts. Art Berman and Joshua Rosenfeld have recently published their depositional model for the Wilcox in the deepwater, a.k.a. the “Whopper
Sand.” Their interpretation argues that a forced regression caused by a sea level drop of over 6,000 feet occurred due to plate tectonic movements which closed off the Gulf of Mexico and shifted deposition about 200 miles downdip. Several Paleogene-aged canyons, the best known being the Yoakum Canyon, formed as a result and fed massive amounts of sand to this new accommodation space. This is an important discussion and I encourage you to check out both sides. The proof is in the data so it will be interesting to hear how much Chevron is willing to share in support of their interpretation.
Reference:
A. Berman and J. Rosenfeld, “A New Depositional Model for the Deepwater Wilcox-equivalent Whopper Sand: Changing the
Paradigm,”World Oil, v. 228, No. 6, June, 2007.
K. Burke and C. Sengor, Tectonic Escape in the Evolution of the Continental Crust, in Reflection Seismology: The Continental
Crust, eds. M. Barazangi and L. Brown, Geodynamics Series, v. 14,
1985, p. 41-53.
J. Rosenfeld and J. Pindell, "Early Paleogene Isolation of the Gulf of Mexico from the World’s Oceans: Implications for
Hydrocarbon Exploration and Eustasy," HGS Bulletin, v. 46, No.
3, November, 2003.