Variations of the authigenic 10Be/9Be-ratio in marine sediments during the Laschamps event and their use for dating of marine sediments

The atmospheric production rate changes of cosmogenic ¹⁰Be are caused by variations of the Earth’s and Sun’s magnetic fields and are recorded worldwide in different climate archives (e.g. ice cores, marine/lacustrine sediments, speleothems). This makes ¹⁰Be a useful tool to synchronize them, thereby overcoming the limitations in precision and accuracy of their individual age models.

Here we present new ¹⁰Be/⁹Be data from a suite of marine sediment cores from the Scotia Sea, Drake Passage and South Pacific covering the Laschamps geomagnetic dipole minimum (~ 41 kaBP). Due to the reduction of the Earth’s magnetic shielding at this time, the ¹⁰Be-production rates roughly doubled, providing an ideal time marker for synchronization. We analyzed the cosmogenic ¹⁰Be and stable ⁹Be in the authigenic fraction of the sediments, which represents the ¹⁰Be/⁹Be signature of the surrounding water. Analyzing the ¹⁰Be/⁹Be ratio reduces the effect of variable particle scavenging rates on ¹⁰Be delivery to the sea floor. We compare our data to existing ¹⁰Be records from other marine sediment cores and ice cores, and to paleomagnetic field reconstructions. We discuss the potential and limitations of using ¹⁰Be/⁹Be ratios for dating marine sediments, and test whether using authigenic ¹⁰Be/⁹Be for synchronization is consistent with the traditional approach of matching climate records to reference sites.