Possible magmatic CO₂ influence on the Laacher See eruption date

The Laacher See Tephra (LST) is a key Late Pleistocene chronostratigraphic unit across Europe, and an accurate date for the deposit is critical for understanding Late Glacial sedimentary sequences. Reinig et al.1 recently used radiocarbon measurements of subfossil trees trapped within the Laacher See eruption’s (LSE) pyroclastic deposits to date the eruption to 13,006 +/- 9 BP, ~130 years older than the previously accepted varve counting (12,880 ± 40 BP2) and 40Ar/39Ar (12,900 ± 560 BP3) age determinations. However, Reinig et al. did not correct for the incorporation of radiocarbon ‘dead’ magmatic CO2 into the growing trees, and here we highlight the possibility that the date is in fact ~130 years too old. The implications of incorporating a high precision yet inaccurate LST age into the European chronostratigraphic framework are substantial, and include the misinterpretation of regional records, the misalignment of climate shifts, and the exclusion of the LSE from consideration as a possible driver of abrupt climate change.