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 Decoding the genome's cryptic language
27.02.2017 | University of California - San Diego

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New pop-up strategy inspired by cuts, not folds

27.02.2017 | Materials Sciences

Sandia uses confined nanoparticles to improve hydrogen storage materials performance

27.02.2017 | Interdisciplinary Research

Decoding the genome's cryptic language

27.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>