The researchers looked at the 18 million years before the asteroid impact that ended the Cretaceous Period and the 4 million years afterward at the outset of the Paleogene Period, when mammals ...

Recommended color coding of stages / F.M. Gradstein and J.G. Ogg -- Appendix 2. Orbital tuning calibrations and conversions for the Neogene period / L. Lourens ... [et al.] -- Appendix 3.