Researchers use heating process to study Pawnee village artifacts

REPUBLIC COUNTY, Kan. -- You might be surprised what you can learn from a campfire. A campfire that has been cold for, say, 300 years.

Stacey Lengyel is hoping she can tell, within 30 years or so, when it was used.

Lengyel, a research associate in anthropology at the Illinois State Museum, is the country's leading authority on archeomagnetic dating, a process built around two phenomena: when heated, magnetic particles reorient themselves to magnetic north; and over time, magnetic north is, literally, all over the map.

"They call it a 'drunken wander,'" Lengyel said. "Around 1600, it was real close to Earth's rotational axis. Now, it is around 75 degrees latitude."

Lengyel is one of scores of people -- mostly volunteers, but also some highly credentialed professionals -- who were enlisted this summer to help uncover new information about a Pawnee Indian settlement in northwest Republic County.

"One of the things we're really hoping to learn is the actual age of the village," said Richard Gould, administrator of the Pawnee Indian Museum. The museum encloses the floor of an 1820s earth lodge. It is surrounded by the remnants of many other structures. The earth has settled where each of the lodges once existed.

The group also wants to learn more about this Pawnee Nation band's lifestyle.

The Republican band

The Kitkehahki band was one of four Pawnee Nation bands. It also was dubbed the Republican band by French traders, who were impressed by the Pawnee's collaborative culture. The Republican name then was adopted for the river and the county.

Band members were hunter-gatherers, Gould said. But they were transitioning to a farming lifestyle. They planted crops in the spring, went hunting for buffalo in the summer, harvested in the winter, and then left to hunt buffalo again in the winter.

The two-week archaeological dig is a project of the Kansas Archaeology Training Program, a venture now in its 33rd year that involves the Kansas Historical Society, the Kansas Anthropological Association, the University of Kansas and Kansas State University.

More than 150 volunteers, some of them students enrolled in KU's Kansas Archaeological Field School, participated in the two-week dig.

Whenever potentially significant fragments were uncovered, their location would be charted before they were moved. Dirt shaved from the floor was bagged and then shaken through a series of increasingly fine meshes.

The team was looking for any telltale objects, such as seeds, tools or building materials, that offered insights into the band's daily lives.

The archeomagnetic dating is a rather technological process. Once potential samples have been identified, their location and orientation are precisely measured, Lengyel said. About a dozen 1-inch cubes are then excised, encased to preserve them, then taken to a lab.

The chunks are then progressively demagnetized until their natural remnant magnetism can be measured, she said. The objects may have been partially magnetized by nearby lightening strikes, for example, or if they were stored near objects with strong magnetic fields. These weaker magnetic fields must be removed.

First their magnetic fingerprint is taken, and then they are slightly demagnetized. The process is repeated several times; each time weaker magnetic signals are purged. Eventually all that is left is the baseline magnetic signal, she said. If the material was fired to about 500 degrees Celsius or more, the magnetic field will point to where magnetic north was located at the time.

"The best dates we can get are within a 30-year time period," Lengyel said.