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.