15 de abril de 2024
Bonilla-Alba, R., Gómez-Paccard, M., Pavón-Carrasco, F. J., Campuzano, S. A., Beamud, E., Martínez-Ferreras, V., Gurt-Esparraguera, J. M., Ariño-Gil, E., Martín-Hernández, F., & Osete, M. L. (2024). First Full-Vector Archeomagnetic Data From Central Asia (3 BCE to 15 CE Centuries): Evidence for a Large Non-Dipole Field Contribution Around the First Century BCE. Journal of Geophysical Research: Solid Earth, 129(2), e2023JB027910. https://doi.org/10.1029/2023JB027910
Abstract
Unraveling the short-term behavior of the Earth’s past geomagnetic field at regional scales is crucial for understanding its global behavior and, thus, the dynamics of the deep Earth. In this context, obtaining accurate full-vector geomagnetic field records from regions where archeomagnetic data are absent becomes essential. Here, we present the first full-vector archeomagnetic data from Central Asia, derived from the analysis of nine archeological kilns sampled in South Uzbekistan, dating back to the period between 200 BCE and 1429 CE. To obtain these new data, we conducted thermal and alternating field demagnetization procedures, along with Thellier-Thellier paleointensity experiments, including partial thermoremanent magnetization checks, thermoremanent magnetization anisotropy and cooling rate corrections. The comparison between the new data, previous selected data from Central Asia, and available global models reveals important differences between approximately 400 BCE and 400 CE, especially concerning the geomagnetic field intensity element. In order to investigate this in detail, we have developed a regional update of the SHAWQ global models family by incorporating, for the first time, high-quality data from Central Asia. The results suggest that this deviation is linked to non-dipolar sources of the geomagnetic field in Central Asia reaching a maximum contribution around the first century BCE. According to the updated global paleoreconstruction, this non-dipole feature, manifested at the Earth’s surface as low intensities, is associated with the presence of a reversed flux patch at the core-mantle boundary beneath this region.