Series of global maps showing virtual geomagnetic pole paths as calculated from the Black Sea paleomagnetic directional record
Virtual geomagnetic pole (VGP) paths calculated from the Black Sea paleomagnetic directional record. These paths represent the successive magnetic pole positions projected onto Earth’s surface, which are composed of individual records of reconstructed magnetic field directions (the paleomagnetic remanence) at a specific location and a specific point in time. The different panels in the figure illustrate snapshots in time where excursions of the magnetic field took place. The contrasting nature of excursions are captured in these results, both in the movement of the pole as well as in the duration of excursions. For example, during the Laschamps excursion (panel b) the geomagnetic field appears to fully reverse and remain stable for a brief period of time, only to fall back into a normal polarity state, all occurring within 1,500 years. Credit: Liu et al. [2020], Figure 9
Source: Journal of Geophysical Research: Solid Earth

Detailed reconstruction of the paleomagnetic field provides important insights into the dynamic features of Earth’s magnetic field, comprising its past field strength and directions. Such details are arguably best recorded in sediments characterized by high and continuous deposition rates, which allows resolving continuous changes of the magnetic field over thousands of years.

Liu et al. [2020] present one of the most detailed paleomagnetic records ever produced, from a sedimentary archive in the southeastern Black Sea. The record spans nearly 55,000 years with a resolution down to 40 years per sample. Even more impressively, they manage to reproduce the details in the paleomagnetic field variations recorded in 16 different sediment cores, illustrating the importance of reproducing results in order to obtain reliable information on the intricacies of the paleomagnetic field.

The stacked paleomagnetic record reveals details on three key excursions that occurred in the last 70,000 years: the Norwegian-Greenland Sea (64.5 ka), Laschamps (41.2 ka) and Mono Lake (34.5 ka) excursions. Importantly, the study provides new insights into the duration, magnetic pole movement and intensity of the magnetic field during these three excursions.

Citation: Liu, J., Nowaczyk, N. R., Panovska, S., Korte, M., & Arz, H. W. [2020]. The Norwegian‐Greenland Sea, the Laschamps, and the Mono Lake excursions recorded in a Black Sea sedimentary sequence spanning from 68.9 to 14.5 ka. Journal of Geophysical Research: Solid Earth, 125, e2019JB019225.

—Bjarne S. G. Almqvist, Associate Editor, JGR: Solid Earth

Text © 2020. The authors. CC BY-NC-ND 3.0
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