New Evidence of Extraterrestrial Cause for the Cretaceous-Tertiary Extinction——The Abundance of Ruthenium and Its CorrelationWith Iridium

1 Introduction In 1980, L. W. Alvarez suggested a hypothesis that the falling of a largeextraterrestrial body upon the earth caused the extinction event at the end of theCretaceous, according to the extraordinarily high concentration of Ir in K/T boundarydeposits. Since then, studies have indicated that the iridium anomaly distributeswidely in the sections of this age over the world. However, these studies focused onthe abundance of Ir. Little attention was paid to other platinum group metals (PGM).Analyzing the abundance of Ru in boundary samples is very difficult because of its