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Saturday, Apr. 30, 2016

New way of looking into the past

Thursday, December 24, 2009

Jason Titcomb, right, Sanford Museum resident Archeologist along with Sanford Museum Director Linda Burkhart is pictured walking at a Mill Creek archaeological site while using the museum's new fluxgate gradiometer that is a non-evasive tool that deliver pictures of what lies under the soil. Photo contributed
Sanford's gradiometer reads magnetic fields

Last month, the staff at the Sanford Museum conducted a field exercise to test a piece of equipment that was recently obtained by the museum.

Their new fluxgate gradiometer is a device that is a non-evasive tool that delivers pictures of what is underneath the soil.

The gradiometer detects and reads magnetic field and deciphers very fine differences in the magnetic field.

Jason Titcomb, Sanford Museum's resident Archeologist, along with Sanford Museum Director Linda Burkhart, devised a test of the gradiometer by surveying a known archaeological site that was close to home.

The Chanyata site, in Buena Vista County was chosen due to the fact that it had been previous expeditions on that site, so the Sanford Team would expect to know what to find at the site.

The Chanyata site is one of only four Mill Creek sites that have never been plowed. The site is situated on an upland landform over looking Brooke Creek.

There were early excavations in the 1930's and 1940's but in the 1970's more extensive excavations took place under the direction of Joseph Tiffany as part of his dissertation research. Apart from these projects no other archaeological research has been conducted at the site.

The gradiometer work had several objectives, first as an attempt to correlate topographic features with possible subsurface archaeology.

A second objective of the survey was to test the equipment's ability to relocate previous archaeological excavation at the site.

An observer cannot see where portions of the excavations took place when visiting the site after the grass is cut short, but not in its entirety. However, the major goals of the survey were to determine whether the site was fortified, or possible house locations and other evidence of prehistoric activity.

The Mill Creek Indians were farmers that lived in this region 900 years ago. Titcomb stated that there are roughly 30 Mill Creek sites in Northwest Iowa. Unlike Plains Indians who lived a migrant life style, the Mill Creek Indians built huts and storage bins for their food. It is long thought that many of these villages also had walls surrounding them.

Using the gradiometer measures local magnetic fields. Buried materials often produce a slight distortion of the earth's magnetic field called anomalies. Anomalies distortions are what the instrument is detecting on a survey.

For this project the Sanford team marked the area into 20 x 20 meter blocking grids. Within each block or survey unit the gradiometer was passed in transects 50 cm across the entire grid.

A single survey grid with these parameters has 40 transects. The instrument collects data at regular intervals, and for this survey was recorded at a rate of eight readings per second. Once a survey grid is completed the data can be downloaded into to a notebook computer in the field and a map can be produced on site. Upon reviewing the data, Titcomb could even make out on a map where the previous excavations had been dug while at the site.

Titcomb indicated that future plans regarding the gradiometer equipment, "We can now look at several villages."

"Where they all fortified?" is one question Titcomb would like to find answers too. "What would have taken us years, now we could do it in a summer" said Titcomb. "Having this equipment gets us to ask a lot bigger research questions. Are we now able to re-examine previous sites and see what we've missed before?" asked Titcomb"

"The sky's the limit, with this technology we can take it anywhere" said Titcomb.

The gradiometer was purchased with funds from the Sanford Museum Association and many individual donors that contributed to make this tool possible for the museum's research.

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