K-T境界けーてぃーきょうかいMeanings1nounK-T boundarygeologyGeological term for the boundary between the Cretaceous and Tertiary periods, often associated with the mass extinction event.K-T境きょう界かいにはイリジウムが多おおく含ふくまれている。The K-T boundary contains a high concentration of iridium.