title: Determining chondritic impactor size from the marine osmium isotope record.
abstract: Decreases in the seawater 187Os/188Os ratio caused by the impact of a chondritic meteorite are indicative of projectile size, if the soluble fraction of osmium carried by the impacting body is known. Resulting diameter estimates of the Late Eocene and Cretaceous/Paleogene projectiles are within 50% of independent estimates derived from iridium data, assuming total vaporization and dissolution of osmium in seawater. The variations of 187Os/188Os and Os/Ir across the Late Eocene impact-event horizon support the main assumptions required to estimate the projectile diameter. Chondritic impacts as small as 2 kilometers in diameter should produce observable excursions in the marine osmium isotope record, suggesting that previously unrecognized impact events can be identified by this method.
authors.affiliation: Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822-2225, USA. paquay@hawaii.edu
authors.forename: François S
authors.initials: FS
authors.lastname: Paquay
authors.forename: Gregory E
authors.initials: GE
authors.lastname: Ravizza
authors.forename: Tarun K
authors.initials: TK
authors.lastname: Dalai
authors.forename: Bernhard
authors.initials: B
authors.lastname: Peucker-Ehrenbrink