A compilation of high-quality paleointensity determinations from dated archeological sites in Uzbekistan from 600 BC to 600 AD.
A compilation of high-quality paleointensity determinations from dated archeological sites in Uzbekistan from 600 BC to 600 AD. New data are from Kurganzol (red dots), Kampyr Tepe (light blue dots) and Termez (purple dots); largest dots indicate best quality. The beige curve is the fit to all data points from the compilation with the beige shading indicating the 95 percent uncertainty envelope. The new data show a minimum of 43 µT around 100 BC to 0 AD and are in line with high values of 70-75 µT from 600 to 400 BC. The blue, red, pink, and green curves represent the intensity retrieved for the same location from various geomagnetic field models that display a markedly smoother field behavior than the actual observations. Credit: Bonilla-Alba et al. [2021], Figure 5
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Solid Earth

We know that Earth’s magnetic field is dominantly a dipole field. However, when zooming in it is spatio-temporally extremely variable. Proper documentation of this variability makes use of dated pottery and other archeological artifacts and offers crucial insight into the generation of the field and delivers a high-precision archeological dating tool at the same time.

Bonilla-Alba et al. [2021] have established a high-quality paleointensity master curve (a curve that describes the intensity of the geomagnetic field as a function of time in years) for Uzbekistan in southwest Asia above Afghanistan primarily based on three key sites (Kurganzol, Kampyr Tepe, and Termez) close to the Afghanistan border and integrating all known reliable Uzbekistan paleointensity data from 600 BC to 600 AD (transferred from their respective location to 37.3°N, 67.2°E, the location of Termez).

Starting at 500 AD the field gradually decays from 55 to 43 & μT at 0 AD, it stays low until 100 to 200 BC before it increases to 75 μT at 400 BC; it hovers between 70 and 75 μT until 600 BC. The high-intensity feature is a few hundred years younger (and probably less spike-like) than the infamous Levantine Iron Age Anomaly (LIAA) at approximately 1100 to 900 BC located approximately 2000 kilometers to the west. The LIAA is argued to migrate westward, so the high intensity feature observed in the present study must represent a distinct, previously unknown, geomagnetic feature testifying a field less smooth than predicted by geomagnetic field models.

Citation: Bonilla-Alba, R., Gómez-Paccard, M., Pavón-Carrasco, F. J., Río, J. d., Beamud, E., Martínez-Ferreras, V., et al. [2021]. Rapid intensity decrease during the second half of the first millennium BCE in Central Asia and global implications. Journal of Geophysical Research: Solid Earth, 126, e2021JB022011. https://doi.org/10.1029/2021JB022011

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

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