New paleointensity experiments were conducted using the IZZI protocol (a variation on the Thellier‐Thellier method) on 289 specimens from 54 baked pottery fragments collected from four archeological sites in the American Southwest. Anisotropy experiments were conducted to correct for anisotropy of remanence, a common problem in archeological material. Additionally, the effect of cooling rate was evaluated and the calculated paleointensity values were adjusted accordingly. Using the Thellier graphical user interface program, the specimen results were analyzed, averaged by sample (i.e., pottery fragment), filtered for the highest quality, and converted to Virtual Axial Dipole Moments (VADMs). Stylistic evidence, historical documentation, and dendrochronology analyses provide age constraints with up to decade resolution for the VADM results. We compared these new results with the highest quality previously published paleointensity values from the Four Corners region of the American Southwest—defined here as the four states of New Mexico, Arizona, Utah, and Colorado. None of the previously published data were corrected for cooling rate and only some were corrected for anisotropy, resulting in a systematic bias between data sets. To accommodate this difference, an estimated cooling rate correction was applied to all the previously published data. No correction can be made for anisotropy as this is specimen specific. Our estimated cooling rate correction and the empirical correction applied to the new data both require an estimation of the historical cooling rate of the pottery. Experimental pottery firings using one ancient technique and outfitted with thermocouples were conducted to determine the historical cooling rate.
Archaeomagnetism applies many of the techniques of paleomagnetism to samples of anthropogenic origin. The materials most often studied are those heated by past peoples (hearths, burned floors, pottery, etc.) because the heating and subsequent cooling of the material generally preserve a stable and measurable magnetization. These heated anthropogenic materials hold tremendous potential for contributing to the understanding of variations in Earth's magnetic field over the last several thousand years because
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