An Ir anomaly of 61 ng/cm**2 was found in Deep Sea Drilling Project Hole 577B at the same stratigraphic level as the Cretaceous/Tertiary boundary defined by nannoplankton. This close correspondence supports the asteroid-impact theory for the Cretaceous/Tertiary boundary extinctions.
86-577B-1-4,72-73 indicates location of Cretaceous/Tertiary boundary as determined by nannofossil biostratigraphy.
Supplement to: Michel, Helen V; Asaro, Frank; Alvarez, Walter; Alvarez, Luis W (1985): Elemental profile of iridium and other elements near the Cretaceous/Tertiary boundary in Hole 577B. In: Heath GR; Burckle LH; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 86, 533-538