Map centered on the North Pole plotting archived data from multiple sources.
On the map centered on the North Pole, the declination (deviation from the geographic north) and inclination (angle with the horizontal) of the geomagnetic field have been recalculated to a virtual geomagnetic pole (VGP) for each location under the assumption of a true geocentric dipole field. Via this way of plotting, small deviations from the true dipolar field are translated into a seemingly migrating magnetic pole, tracing a VGP path as function of time describing the paleosecular variation (PSV). The authors put all archived data on today’s accepted standards; 1185 archeological sites passed the filters (out of 5377 sites). The archives represent 60 years of effort from three of America’s foremost archeomagnetists and their students (scientists who utilize dated archeological artifacts to create a master PSV curve that can subsequently be used to date other archeological artifacts): DuBois (circles), Wolfman (diamonds) and Eighmy (triangles). The data are colored by century from 600 to 1900 CE (Common Era). Credit: Jones et al. [2021], Figure 6
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Solid Earth

The geomagnetic field shows regional changes in declination (angle with geographic north), inclination (angle with the horizontal), and intensity on centennial time scales, known as paleosecular variation (PSV). By making use of dated archeological artifacts, so-called PSV master curves have been put together tracing the field behavior for the most recent millennia for several regions on Earth, with a focus on declination and inclination trends because getting good quality intensity from archeological artifacts is considerably more tedious.

Jones et al. [2021] have unlocked the vast USA PSV legacy database that was until now surprisingly poorly accessible. Those legacy data represent 60 years of research effort and was resting in the laboratory archives of three of America’s archeomagnetism giants: Dubois, Wolfman, and Eighmy. The authors performed a Herculean job: they had to return to the raw data archives, put all data on common and modern standards, essentially redo the data interpretation, and apply today’s reliability criteria which are much stricter than those in use in the 1960s-1990s (only 1185 out of 5377 archeological sites passed).

The result is worth the effort: A new robust regional PSV curve is established for the Four Corners region in the USA that reconciles previous partly conflicting curves, enabling precise dating of Native American structures. Further, having these data now available in accessible data bases will lead to significantly improved geomagnetic field models (both regional and global).

Citation: Jones, S. A., Blinman, E., Tauxe, L., Cox, J. R., Lengyel, S., Sternberg, R., et al. [2021]. MagIC as a FAIR repository for America’s directional archaeomagnetic legacy data. Journal of Geophysical Research: Solid Earth, 126, e2021JB022874.

—Mark J. Dekkers, Editor, JGR: Solid Earth

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