Milankovitch cycles and comet catastrophes: Carbon isotope variations in the Late Paleocene-Early Eocene.

摘要

I demonstrate that a large perturbation in the global carbon isotope record at the Paleocene/Eocene boundary is mirrored in smaller perturbations throughout the late Paleocene-early Eocene. The smaller perturbations occur at maxima in the eccentricity of Earth's orbit around the Sun and are the expected result of precession forcing of a system with a built-in long time constant, i.e. the residence time of carbon in the ocean-atmosphere-biosphere reservoir. The carbon isotope excursion at the Paleocene/Eocene boundary is different both in amplitude and in timing: it is roughly twice as large as any of the other perturbations and occurs out of phase with maxima in eccentricity. This suggests that the trigger for the Paleocene/Eocene carbon isotope excursion was not integral to the biogeochemical carbon cycle. A plausible catastrophic explanation for the carbon isotope excursion is a comet impact, and I present data supporting an impact at the Paleocene/Eocene boundary.