The iridium anomaly marks the elevated concentration of iridium in sedimentary deposits of the Cretaceous-Paleogene boundary. The iridium is said to come from the impactor, which is supposed to have much higher iridium contents than Earth's crust.

What about other metals? Is there an observed increase of other elements as well? For example, osmium is another extremely rare element in the crust. Is there an osmium anomaly as well? If not, why is the anomaly restricted to iridium and not the other metals?


According to the conference article Can Siderophile Element Abundances and Ratios across the K-Pg Boundary be used Discriminate between Possible Types of Projectiles?, (Belza et al. 2013) state that the enrichment is not only in Iridium, but also in the other Platinum Group Elements and siderophile elements.

From the article Platinum-group elements (PGE) and rhenium in marine sediments across the Cretaceous– Tertiary boundary: Constraints on Re-PGE transport in the marine environment (Lee et al. 2003) elaborates that from

A traverse across the KTB in the South Pacific pelagic clay core found elevated levels of Re, Pt, Ir, Os, and Ru, each of which is approximately symmetrically distributed over a distance of 1.8 m across the KTB.

(KTB is a reference to Cretaceous-Tertiary Boundary from the article).

In a re-evaluation of geochemical data in Reevaluation of siderophile element abundances and ratios across the Cretaceous–Paleogene (K–Pg) boundary: Implications for the nature of the projectile (Goderis et al. 2013), took into account several more studies (published and unpublished), find that cobalt, chromium and nickel display in some places, an elevated concentration; however, the Co/Cr, Ni/Co, Ni/Cr, Co/Ir, Ni/Ir and Cr/Ir ratio are considerably higher than that of the average continental crust, which the authors suggest is consistent with chondrites.

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