Multiple 10Be records revealing the history of cosmic-ray variations across the Iceland Basin excursion

Abstract Cosmogenic 10 Be is a proxy of cosmic-ray flux, and its natural records provide vital information about the past intensity variability of the geomagnetic field and solar activity. 10 Be records also serve as powerful tools for global synchronization among a variety of paleoarchives and for elucidating sedimentary processes on natural remanent magnetization acquisition. However, high-resolution (multi-decadal to multi-centennial) records of 10 Be are scarce, especially those older than several tens of thousands of years. Here we present multiple high-resolution 10 Be records of the Iceland Basin geomagnetic excursion interval (ca. 170–200 kyr ago) obtained from sediment cores (authigenic 10 Be/ 9 Be ratio) and an ice core (atmospheric 10 Be flux). Comparing sedimentary 10 Be records with relative paleointensity from the same cores, we found differences in the magnetic lock-in depth, even between adjacent cores. The 10 Be-proxy records from the sediment and ice cores exhibit common characteristics: an asymmetric large-scale variation, a ∼7-kyr quasi-plateau around the maximum with a characteristic mid-term depression, and multi-millennial fluctuations in cosmic-ray flux during this interval. Minimal-synchronized and stacked 10 Be records show that maximum cosmic-ray flux occurred 188.5–190.0 kyr ago and was double the present flux. A wavelet analysis of the stacked curve reveals dominant 4-kyr and secondary 8-kyr periodicities, both of which can be interpreted as intrinsic geomagnetic cycles. The wavelet spectrum of the high-resolution ice-core record shows a periodicity of 1.7 kyr and somewhat intermingled multi-centennial cycles around the maxima of 10 Be, which likely represent solar cycles in this period. High-resolution 10 Be records from multiple paleoarchives provide both a robust proxy record of cosmic-ray flux and a valuable tool for detailed global synchronization based on cosmic-ray variations.