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Cal Poly Pomona Experts Guide


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April 12, 2018
Prof. Thomas Fenn with local Tuareg guide in the Southern Sahara, outside of Agadez in Central Nigeria.

Thomas Fenn studies historical long distance trading relationships in Africa using chemical and isotopic evidence from ancient glass beads. The lecturer in the Geography and Anthropology Department recently received a $200,000, three-year National Science Foundation (NSF) grant to extend his research to early glass bead making in India.


“There is this really amazing story that’s being captured by the glass beads in archeological sites in Southern Africa,” said Fenn.  “They illustrate the rise and fall of empires controlling the flow of goods and materials across the Indian Ocean. In some of these archeological sites, the glass beads are the only imported materials we find there.”


“For example, during the period from about 500 to 1000 AD,” said Fenn, “glass beads were coming out of the Middle East…and working their way down the East African coast to future archeological sites. Right around 1000 AD you see a dramatic shift in the chemical and isotopic composition of the beads that coincides with a lot of upheaval in the Middle East and a major earthquake with a tsunami that supposedly wipes out several port cities in the gulf of Arabia.”


“The Cholla dynasty in Southern India rises to power and captures control of the Indian Ocean trade networks. All of a sudden in east and southern Africa you have a dramatic shift in bead composition that looks consistent with bead production in Southern India,” explained Fenn.


Around 1250 AD, Middle Eastern cultures recapture control of the trade routes, and there is another shift in the isotopic composition of the beads, more consistent with earlier glass beads from the Middle East, though slightly different.


“About 200 years later,” continued Fenn, “there’s a rise of several other powers, including the Moghul Empire in northern India. Again there’s a corresponding shift in the glass isotopic composition, consistent with India. It’s a different recipe than the early phase of Indian beads so perhaps they’re from a different location in India.”


The NSF grant, to be split by Fenn and his colleague Laure Dussubieux at the Field Museum in Chicago, will fund research into the evolution of early Indian glass and the interplay of long-distance Indian Ocean trade and overseas demand on the development of glass production centers in India, from approximately 500 BC to 1500 AD.


Over the next two years, the researchers will visit three regions of India that have evidence of glass making and the geologic materials necessary to create glass – quartz, a flux material to lower the melting point of the quartz (normally an alkali salt), and a stabilizing material (usually calcium found in lime and shells, though in India alumina is often used).


In summer 2018, Fenn and two Cal Poly Pomona undergraduate students will travel to the southeastern coast and northwestern region of India to gather soil samples near the headwaters of rivers that run to the east and sites near the mouths of rivers flowing to the west. In 2019, the researchers will focus on sites along the Ganges River.


Back at their home institutions, the researchers will melt each sample to see whether they can make glass. If they can, the glass will undergo chemical analysis to see if it corresponds to any ancient glass samples. Raw materials that have major, minor and trace elements similar to compositions of already well-known ancient glass groups in India will be submitted for isotopic analysis for lead, strontium and neodymium to provenance coloring ingredients. Some of that analysis work will be done at Cal Poly Pomona.


The isotopic analysis will be key to independently connecting the glass to raw materials and therefore to probable regions of raw glass and bead manufacturing, explained Fenn. This will allow the team to build on knowledge about economic connections between countries to each other through trade on the Indian Ocean.


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