North American Database of Archaeological Geophysics
North American Database of Archaeological Geophysics
Abstract/Summary:
Project Name: Chetro Ketl (Chaco Canyon National Monument), NM;
Reference: Loose, R.W., and T.R. Lyons. (1976). The Chetro Ketl Field: A Planned Water Control System in Chaco Canyon. In Remote Sensing Experiments in Cultural Resource Studies: Non-Destructive Methods of Archeological Exploration, Survey, and Analysis. Reports of the Chaco Center. National Park Service and University of New Mexico, Albuquerque, New Mexico. 1:133-153.
The purpose of this paper is to estimate the amount of land under prehistoric cultivation in Chaco Canyon National Monument by using remote sensing techniques to identify ancient agricultural fields and associated water control features. Establishing the relationship between Chacoan population size and the agricultural techniques used to support the prehistoric people of the Chaco has long been an unsolved problem. In a project undertaken by the Chaco Center, two parts of the above mentioned problem were addressed: to develop a technique for recognition of Anasazi agricultural features within the canyon, and once the technique was established, to attempt to quantify the total amount of land under cultivation at any given point in time.
In the process of developing a technique for recognition of Anasazi agricultural features, a set of measurements was taken with an electron spin magnetometer. This instrument measured slight precession of electron orbits caused by minute changes in ambient magnetic fields. Changes in magnetic moment of less than 2 gamma were recorded over an area which measured approximately 35 meters on a side. The values were averaged and interpolated and then printed out as a 2.4 gamma contour interval map. A rectangular feature approximately 15 by 20 meters was apparent in the magnetic contours and was the same size as plots visible in aerial photographs. The center of the plot showed the highest magnetic moment, while the borders had the lowest magnetic alignment. This was good evidence that irrigated, earth bordered garden plots were indeed responsible for the observed rectilinear patterns.