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 Repairing damaged hearts with self-healing heart cells
22.08.2017 | National University Health System

nachricht Biochemical 'fingerprints' reveal diabetes progression
22.08.2017 | Umea University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>