Next >
< Previous
Main Page
On Tar's Trail at the Recent SAA Conference in Vancouver
Tuesday, April 8, 2008
Blog Author: Ellery Frahm
![Keywords: bitumen, tar, asphalt, organic chemistry, Olmec, sourcing, economics
I've posted about bitumen before: here and here. I did view this poster at SAA -- it was part of the "Archaeometry and Artifact Studies in Mesoamerica and Middle America" session on Thursday evening -- but only briefly, and I'll admit that I don't recall it well. I have good excuses, though... really. For one, I was eagerly awaiting posters in a session called "Innovations in Ceramic Analysis"... but, by the time I left the exhibit hall, there was only one of the three posters in the session up -- how disappointing! Another reason is that, well, I was distracted from this good poster by a nearby bad one -- no, I'm not saying which one. Lastly, an evening session on the first day is a horrid idea -- hear that SAA? Everyone is meeting up with conference friends and hungry for dinner after a rushed (and expensive) lunch between morning and evening sessions, and I, too, was eager for dinner with colleagues. But it looks like I walked too quickly past this interesting research on Olmec use of bitumen.
Above: Bitumen oozing out of carbonate boulders on a hot summer day. Credit: Natural Resources Canada.
Excerpts from Science:
Following an Asphalt Trail to Ancient Olmec Trade Routes
By Heather Pringle
News Focus: Society for American Archaeology Meeting, 26-30 March 2008, Vancouver, Canada
When archaeologists teach about the Olmec culture, they flash images of massive stone heads, sculpted for a sophisticated elite who ruled the swampy lowlands of Mexico from 1200 to 400 B.C.E. But a poster by archaeologist Carl Wendt of California State University, Fullerton, throws the spotlight on Olmec commoners. Once dismissed as simple maize farmers, the ordinary Olmec apparently mastered a sophisticated technique for making asphalt, crucial to sealing wooden boats, and they traded the valuable substance to others.
This research will shed new light on previously invisible trade routes, says Olmec expert David Grove of the University of Florida, Gainesville. Because Wendt can distinguish asphalt from various sources, Grove notes, the work "adds a significant new 'artifact' [asphalt] to the small list of artifacts that can be used in the study of trade in Mesoamerica at 1000 B.C.E."
Earlier archaeologists paid little attention to asphalt, occasionally noting its presence on sacred figurines, tool handles, and potsherds. But during excavations at the Olmec site of Paso los Ortices, Wendt discovered a pit containing 250 kilograms of asphalt slabs. He wondered how the Olmec processed asphalt, what they used it for, and whether elites controlled its manufacture.
To find out, his team studied thin sections of asphalt lumps from Olmec sites with a petrographic microscope. They noted even patterns of sand particles and impressions of decomposed plants, suggesting that these silica-rich materials were intentionally mixed in during heating to add structure to the asphalt. The team also identified and sampled more than 50 asphalt seepages in the Olmec region.
Then they experimented, adding different plant additives and heating samples in clay pots over fires to produce an asphalt that was both flexible enough to apply to figurines and other objects and yet hard enough to resist melting in the sun. "We had a bear of a time trying to get it to that state," says Wendt. Some samples were simply too watery. But Wendt and his team processed other, stickier samples in just a few hours; they found that the leaves of a plant the local inhabitants use to wrap tamales produced the best asphalt. . .
To read the rest of the article, visit the Science website:
http://www.sciencemag.org/cgi/content/full/320/5873/174a
These webpages are best viewed with the newest version of your favorite web browser. The views and opinions expressed in this page are strictly those of the page author. The contents of this page have not been reviewed or approved by the University of Minnesota. Links on these pages to external websites are provided as a convenience, not an endorsement of either views expressed at or products promoted by those sites, so visit them at your own risk. Top photo: sunset over the excavations at Tell Mozan in northeastern Syria, taken by Ellery Frahm.
News articles come from various sources, and the sources are cited in each post. Excerpts from these articles are used under fair use. Use of this copyrighted material has not always been specifically authorized by the owner. The material has made available here in order to advance understanding of geoarchaeology, archaeological science, and related fields. This constitutes "fair use" of copyrighted material as described in section 107 of the US Copyright Law: "the fair use of a copyrighted work... for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright." This material is distributed without fee or profit to those interested in it for research or educational purposes. This website is not commercial in any way -- it is nonprofit. There is no advertising on this website.
If you believe your work has been used here in a way that constitutes copyright infringement or your intellectual property rights have been otherwise violated, please provide the following information to the site author: 1. a description of the copyrighted work or intellectual property that you claim has been infringed; 2. a description of where that material is located on this site; 3. your address, telephone number, and email address; 4. a statement by you that you have a good faith belief that the disputed use is not authorized by the copyright owner, its agent, or the law; 5. a statement by you, made under penalty of perjury, that the above information in your notice is accurate and that you are the copyright or intellectual property owner or authorized to act on the copyright or intellectual property owner's behalf; and 6. your electronic or physical signature.](F8C68F3D-586C-4217-8F35-84B91305F6E3_files/shapeimage_2.png)
