English: geological signature, usually a thin band of rock, marking the transition from the end of the Cretaceous Period and the beginning of the Paleogene Period, dated with radiometric methods, at the age of 66.043 ± 0.011 Ma
Japanese: 地質年代区分の用語。顕生代において5回発生した大量絶滅のうちの最後の事件。生物種の最大約75%が絶滅、また99%以上の個体が死滅