Abstract
AbstractSeveral regional secular variation curves of the geomagnetic field have been proposed for Mexico over the last millennia. Despite a fairly large number of archeomagnetic data, these curves remain imprecise because of an uneven quality and geographic distribution, with a lack of data in Northern Mexico. Nine pottery kilns were sampled in Casas de Fuego, an archeological site in the Chihuahua state. These kilns belong to the Casas Grandes culture and were in use between 1250 and 1450 CE. Rock magnetic experiments indicate that the main magnetic phase is a Ti‐poor titanomagnetite in the SD range. Mean characteristic directions per kiln were estimated by alternating field and/or thermal demagnetization, and archeointensities with the Thellier‐Thellier protocol, after correction for anisotropy and cooling effects. The nine directions and eight intensities agree with data from USA and Mexico but do not support the peak in inclination modeled by the Mexican secular variation curve around 1200–1300 CE. For the last millennium, the Western North American curve is consistent with the SHAWQ2k global model, and better reflects the secular variation in Northern Mexico. For intensity, neither the SHAWQ2k model nor the regional intensity curve can depict the rapid secular variation that likely occurs circa 1500 CE. The Casas de Fuego results are the first full vector determinations obtained in Northern Mexico.
Highlights
Direct measurements of the geomagnetic field are available through ground observatories and navigators’ data for the last 400 years (Jonkers et al, 2003) and satellite measurements for the last decades
The Western North American curve is consistent with the SHAWQ2k global model, and better reflects the secular variation in Northern Mexico
The Casas de Fuego results are the first full vector determinations obtained in Northern Mexico
Summary
Direct measurements of the geomagnetic field are available through ground observatories and navigators’ data for the last 400 years (Jonkers et al, 2003) and satellite measurements for the last decades. Only a few dozens of data, generally acquired on volcanic flows are full vector (e.g., Mahgoub, Juárez-Arriaga, Böhnel, Siebe, & Pavón-Carrasco, 2019) Another weakness of the Northern and Central American data set is the inhomogeneous data quality, which clearly impacts the recovery of the secular variation in these regions (e.g., Hervé, Perrin, Alva-Valdivia, Tchibinda Madingou, et al, 2019; Jones et al, 2020). A large proportion of intensity data do not fulfill modern quality criteria, such as the necessity to appropriately correct for TRM anisotropy and cooling rate effects, at least for archeological baked clays (Hervé , Perrin, Alva-Valdivia, Tchibinda Madingou, et al, 2019; Mahgoub, Juárez-Arriaga, Böhnel, Manzanilla, & Cyphers, 2019). This site is part of the Mogollon cultural area, one of the most important in Northern Mexico and Southwestern USA
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