Extreme lowering of deglacial seawater radiocarbon recorded by both epifaunal and infaunal benthic foraminifera in a wood-dated sediment core

For over a decade, oceanographers have debated the interpretation and reliability of sediment microfossil records indicating extremely low seawater radiocarbon (inline-formula¹⁴C) during the last deglaciation – observations that suggest a major disruption in marine carbon cycling coincident with rising atmospheric inline-formulaCO₂ concentrations. Possible flaws in these records include poor age model controls, utilization of mixed infaunal foraminifera species, and bioturbation. We have addressed these concerns using a glacial–interglacial record of epifaunal benthic foraminifera inline-formula¹⁴C on an ideal sedimentary age model (wood calibrated to atmosphere inline-formula¹⁴C). Our results affirm – with important caveats – the fidelity of these microfossil archives and confirm previous observations of highly depleted seawater inline-formula¹⁴C at intermediate depths in the deglacial northeast Pacific.