Geomagnetic intensity variations for the past 8 kyr: New archaeointensity results from Eastern China

- New archaeointensity results spanning the last 7 kyr in eastern China.
- An extremely low paleointensity of ∼2×1022 Am2 at ∼2250 BCE.
- A six-fold increase of VADM (2×1022-13×1022 Am2) between ∼2250 BCE and ∼1300 BCE.
- Reliable inputs to improve the regional model of Eastern Asia and global models.
- The intensity spike around ∼1000 BCE observed in the Middle East may not be global.

In this study, we have carried out paleointensity experiments on 918 specimens spanning the last ∼7 kyr, including pottery fragments, baked clay and slag, collected from Shandong, Liaoning, Zhejiang and Hebei Provinces in China. Approximately half of the specimens yielded results that passed strict data selection criteria and give high-fidelity paleointensities. The virtual axial dipole moments (VADMs) of our sites range from ∼2×1022 to ∼13×1022 Am2. At ∼2250 BCE our results suggest a paleointensity low of ∼2×1022 Am2, which increases to a high of ∼13×1022 Am2 by ∼1300 BCE. This rapid (less than 1000 yrs) six-fold change in the paleointensity may have important implications for the dynamics of core flow at this time. Our data from the last ∼3 kyr are generally in good agreement with the ARCH3k.1 model, but deviate significantly at certain time periods from the CALS3k.4 and CALS10k.1b model, which is likely due to differences in the data used to constrain these models. At ages older than ∼3 ka, where only the CALS10k.1b model is available for comparison, our data deviate significantly from the model. Combining our new results with the published data from China and Japan, we provide greatly improved constraints for the regional model of Eastern Asia. When comparing the variations of geomagnetic field in three global representative areas of Eastern Asia, the Middle East and Southern Europe, a common general trend of sinusoidal variations since ∼8 ka is shown, likely dominated by the dipole component. However, significant disparities are revealed as well, which we attribute to non-dipolar components caused by movement of magnetic flux patches at the core-mantle boundary.