Anomalous > 2000-Year-Old Surface Ocean Radiocarbon Age as Evidence for Deglacial Geologic Carbon Release

Geologic carbon from seafloor volcanism may influence late Pleistocene glacial terminations by increasing the global inventory of the greenhouse gas CO2. However, the evidence for geologic carbon flux associated with deep sea volcanism has been, so far, equivocal. Here, we construct a regional, glacial-deglacial carbon budget of the volcanically active Gulf of California using microfossil C-14 measurements and find results consistent with an increased addition of geologic carbon related to local seafloor volcanism during the deglaciation. Our estimates point to enhanced geologic carbon flux both before and during the last deglaciation that generally occur alongside carbonate preservation. This leads us to suggest that the carbon was added in the form of partially neutralized, C-14-free bicarbonate associated with known Gulf sedimentary processes-a carbon source that would have a minimal effect on atmospheric CO2.