Reconciling the Greenland ice-core and radiocarbon timescales through the Laschamp geomagnetic excursion

Abstract

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A global environmental crisis 42,000 years ago

“…Notably, the steep rise in D 14 C commences at 42.35 ka, with a peak value of 782 per mil (‰) occurring at 41.8 ka, 300 years before the full Laschamps reversal. This is the highest atmospheric 14 C concentration yet reported of the pre-anthropogenic radiocarbon time scale (22,23,25) (see supplementary materials). The peak D 14 C value reported here occurs during the most weakened phase of the geomagnetic field (5) and is associated with a prominent GSM recorded by 10 Be flux (20) (Fig.…”

“…22 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. 23 Centre of Excellence for Climate System Science, University of New South Wales, Sydney, NSW 2052, Australia. 24 Southern University of Science and Technology, Department of Ocean Science and Engineering, Shenzhen 518055, China.…”

“…The high 10 Be flux has been well described from Greenland and Antarctic ice core records (6,20,21), which reveal synchronous century-long 10 Be peaks across the Laschamps that appear to reflect a series of pronounced Grand Solar Minima (GSM; prolonged periods of low solar activity similar to the Spörer and Maunder Minima: 1410 to 1540 CE and 1645 to 1715 CE), with unknown climate impacts (20,21). By contrast, the associated atmospheric 14 C changes remain poorly constrained (22), preventing precise calibration (23).…”

The dating and correlation of an eastern Mediterranean lake sediment sequence: a 46–4 ka tephrostratigraphy for Ioannina (NW Greece)

“…Radiocarbon dating is frequently applied to develop chronologies spanning the last 50 ka (e.g. Lawson et al ., 2004; Staff et al ., 2019). Beyond the 50 ka bp upper dating limit of radiocarbon, pollen records from terrestrial sites can be correlated to their marine equivalents, and, in turn, to the sea surface temperature (SST) and $${\delta }^{18}{\rm{O}}$$ records therein, which provide age constraints based on alignment to the Greenland ice cores and orbital parameter, (e.g.…”

Dendrochronology and Radiocarbon Dating

“…Similarly, kauri was also measured in decadal blocks across 1300 years around the time of the Laschamps geomagnetic minimum event, showing the strong rise of Δ 14 C caused by the event. The link to a 10 Be reconstruction provided an ice core-based age of 42,500 cal BP, which was 1000 years younger compared to the Hulu cave 14 C ages (Turney et al 2010), possibly resulting from carbon cycle changes causing different signals in 14 C. A detailed discussion is presented in Staff et al (2019). Meanwhile, Scots pine and other sub-fossil trees from Northern Italy sampled at 5-and 10-year resolution show large age variations ca.…”