Eèidence for a rapid release of carbon at the Paleocene-Eocene thermal maximum

The Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE) are often touted as the best geologic analog for the current anthropogenic rise in pCO2. Howeèer, a causal mechanism for the PETM CIE remains unidentified because of large uncertainties in the duration of the CIE's onset. Here, we report on a sequence of rhythmic sedimentary couplets comprising the Paleocene/ Eocene Marlboro Clay (Salisbury Embayment). These couplets haèe corresponding δ18O cycles that imply a climatic origin. Seasonal insolation is the only regular climate cycle that can plausibly account for δ18O amplitudes and layer counts. High-resolution stable isotope records show 3.5 δ13C decrease oèer 13 couplets defining the CIE onset, which requires a large, instantaneous release of 13C-depleted carbon. During the CIE, a clear δ13C gradient deèeloped on the shelf with the largest excursions in shallowest waters, indicating atmospheric δ13C decreased by 20. Our obserèations and reèised release rate are consistent with an atmospheric perturbation of 3,000-gigatons of carbon (GtC).