Determining chondritic impactor size from the marine osmium isotope record.
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.
Paquay
François S
FS
Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822-2225, USA. paquay@hawaii.edu
Ravizza
Gregory E
GE
Dalai
Tarun K
TK
Peucker-Ehrenbrink
Bernhard
B