Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clues to African archaeology found in lead isotopes

28.03.2006
Microscopic specs of lead are offering clues about the enormous cultural changes that swept across northern Africa a thousand years ago.

At The University of Arizona in Tucson, a young archaeologist is analyzing lead traces in artifacts to shed light on the relatively little-understood archaeology of Africa, especially the period marked by the spread of the new religion of Islam.

Thomas R. Fenn, a doctoral student in the UA anthropology department, is unraveling evidence of centuries-old trade patterns across the Sahara Desert by identifying smelted metal artifacts, mainly copper, found in the continent’s sub-Saharan regions.

Fenn will report the results of his work ("Getting to the source of the problem: Lead isotope analysis and provenance determination of ancient African copper artifacts") on Sunday, March 26, at 2 p.m., U.S. Eastern Time at the annual meeting of the American Chemical Society in Atlanta. Fenn’s presentation is in the Georgia World Congress Center, Room C-108.

As Islamic forces moved across northern Africa, they set in motion trading opportunities between the arid lands bordering the Mediterranean and the dense jungles and savannahs south of the Sahara.

One of the questions Fenn wants to answer concerns the sources of copper and other raw materials that became manufactured goods that were traded throughout the region. Specifically, why were metal workers in a sophisticated metallurgical industry in the sub-Sahara importing copper ingots when there were perfectly good copper ore deposits nearby?

Knowing where these and other materials originated, said Fenn, may offer larger insights about not only trade, but also about technologies, economics and social organization. Who controlled bankable natural resources and transportation routes? How was labor distributed in these societies?

David J. Killick, a UA associate professor of anthropology and expert on the archaeology of metallurgy in Africa, said tracing metals is a crucial part of understanding the development of trade in Africa.

"Most of the money circulating in the western half of the Islamic world between the 11th and 16th centuries was minted with gold from sub-Saharan west Africa, and competition for the wealth generated by the trade fueled the growth of major West African states like Ghana, Mali and Songhai," Killick said.

Using a process called lead isotope ratio analysis, or LIA, Fenn has examined more than 100 Iron-Age artifacts, most of them copper, from sub-Saharan Africa. The experiments were done in the W.M. Keck Isotope and Trace Element Laboratory at the UA. The lab is partially funded by the National Science Foundation and run by Joaquin Ruiz, a professor of geosciences and dean of the UA College of Science.

"LIA is extremely accurate as a forensic tool in identifying lead traces found in metal ores," said John Chesley, a research scientist in the UA department of geosciences who developed the laboratory and analytical techniques for Fenn’s project.

Lead has four different isotopes, three of which occur as the natural decay of uranium and thorium. The isotopic ratios change as a function of time. Smelting doesn’t change the ratios, making them a virtual fingerprint for a metal’s source of origin. Scientists need only about 100 billionth of a gram for analysis.

The trick, said Chesley, is making sure the sample remains completely free of contamination. The process takes about two weeks, but offers a high degree of certainty of linking objects to their source. LIA has been used successfully to determine the sources of non-ferrous metals from sites in other parts of the world for years, but its use in African archaeology is fairly recent.

"In reality, I am dating the deposition of the ores on a geological timescale - millions of years - but I am not dating them within an archaeological time scale," Fenn said. "I am, in fact, using the geological age, derived from the lead isotope ratios, as a means of provenancing raw and refined copper metals, and metallurgical debris, to a potential ore source based on the similarity of their geological age, i.e., their lead isotope ratios, as well as by examining and comparing their chemical compositions."

From his analysis, Fenn theorizes that the ore used to make the copper ornaments and other items found in the sites in West Africa likely came from North Africa. He said merchants there traded gold from regions like present-day Niger for copper from the north via camel caravans across the desert.

Refined copper, Fenn said, likely was prized as a commodity that fit in with the value system of the region, where it was easily worked into ornamental objects and other items that could be bartered for other goods and services.

Jeff Harrison | EurekAlert!
Further information:
http://www.arizona.edu

More articles from Life Sciences:

nachricht Transforming plant cells from generalists to specialists
07.12.2016 | Duke University

nachricht What happens in the cell nucleus after fertilization
06.12.2016 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Predicting unpredictability: Information theory offers new way to read ice cores

07.12.2016 | Earth Sciences

Sea ice hit record lows in November

07.12.2016 | Earth Sciences

New material could lead to erasable and rewriteable optical chips

07.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>