Here we present combined radio-isotopic dating (U-Pb zircon) and cyclostratigraphic analysis of the carbon isotope excursion at the Paleocene/Eocene (P/E) boundary in Spitsbergen, to determine the numerical age of the boundary. Incorporating the total uncertainty from both radio-isotopic and cyclostratigraphic datasets gives an age ranging from 55.728-55.964 Ma, within error of a recently proposed astronomical age of ~55.93 Ma. Combined with the assumption that the Paleocene Epoch spans twenty-five 405 kyr cycles, our new age for the boundary suggests an age of ~66 Ma for the Cretaceous/Paleogene (K/Pg) boundary. Furthermore, our P/E boundary age is consistent with the hypothesis that the onset of the Paleocene-Eocene thermal maximum (PETM) at the boundary occurred on the falling limb of a 405 kyr cycle, suggesting the event was initiated by a different mechanism to that which triggered the other early Eocene hyperthermals
