Abstract

In Chinese loess, the Brunhes-Matuyama (B-M) geomagnetic reversal occurs ∼25 k.y. prior to the age found in marine sediments. This offset has been attributed by some to post-depositional magnetic overprinting of loess, while others have argued it is due to errors in the loess time scale. Here we solve this long-standing debate by exploiting a new method to extract reproducible records of geomagnetic field intensity from loess with 10Be—a proxy for global average geomagnetic field intensity—and using it to show that a pronounced minimum in field intensity (a requirement for dipole field reversal) is recorded in two separate loess records at ca. 780 ± 3 kyr B.P. This timing is synchronous with the B-M reversal timing seen in marine records, verifying the standard loess time scale as correct, but it is ∼25 k.y. younger than the age (depth) of the magnetic polarity reversal recorded in these same Chinese loess sediments, demonstrating that loess magnetic overprinting has occurred.

You do not currently have access to this article.