What marks the boundary between the mesozoic and the cenozoic (called the k-p boundary) ? g?

The extermination of the dinosaurs, the start of a rise to dominance of mammals and a meteorite effect in mexico marks the boundary among the mesozoic and the cenozoic or as named as the k-p boundary. In addition, the cretaceous paleogene (K-Pg) boundary which is previously recognized as the cretaceous tertiary (K-T) boundary is a geological signature typically a thin band of rock.