The Utility of Shell Temper for Ceramic Analysis

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Dr. Evan Peacock and Dr. Brenda Kirkland, Mississippi State University, along with Dr. Virginie Renson, University of Missouri, will undertake research to test a new method for tracing past human population movements and trade networks. Understanding ancient demographic trends and economic links is key for unraveling the history of any particular area. How interconnected were settlements in the past? Where were goods produced, and how did they flow from market to consumer? Did particular settlements gain prominence due to an ability to control the flow of goods? How do ancient population movements relate to the historically known distribution of Native American or other descendant groups? Interest in such topics has grown as new instruments for chemically analyzing artifacts have been developed. For example, archaeologists chemically analyze ancient pottery sherds using a variety of methods and try to match them to clay samples taken in the field, to determine where the pottery clay was originally obtained. While this approach has produced some exciting results, it is complicated by a number of factors. Many different clay beds can occur over a small area, a clay bed can be chemically homogenous over a very large area, or potters may have mixed different clays together when making pottery. Addressing this problem is necessary if the promise of ceramic sourcing for addressing questions of anthropological and historical import is to be more fully realized. The research will contribute to understanding the prehistory of United States Native Americans and serve to inform Americans on an important part of the country's past.An alternative to chemically sourcing pottery clay is to analyze other materials mixed with the clay by potters; such extra materials are called "temper." Beginning about AD 1000, crushed freshwater mussel shell was used as pottery temper over a huge expanse of eastern North America. As freshwater mussels grow, they build the chemical signature of the stream waters they inhabit into their shells. Shells from different drainages therefore are chemically distinct. By chemically comparing shells discarded as food waste with temper from pottery at different sites, archaeologists theoretically can pinpoint the precise stream, or even stream segment, where the pottery was made. Dr. Peacock and his colleagues will test this new method by analyzing shells and shell-tempered pottery recovered from several sites in the Yazoo Basin of Mississippi, a vast landscape drained by many different streams that connected the mid-continent with the Gulf of Mexico and provided ready travel routes along which pots or other artifacts may have been traded centuries ago. Analysis will be done using an Inductively Coupled Plasma-Mass Spectrometer, for which only small amounts of shell or shell temper are needed. The use of individual elements, such as isotopes of Strontium, to refine the method, also will be explored. As a particular archaeological test case, pottery previously identified as stylistically "exotic" and discarded shells from the Lake George site, a massive, ca. 1,000 year-old settlement in Yazoo County, Mississippi, will be analyzed. If successful, this method should be applicable to any place in the world where shell-tempered pottery was produced.