No geochemical evidence for an asteroidal impact at late Devonian mass extinction horizon

Details No geochemical evidence for an asteroidal impact at late Devonian mass extinction horizon No geochemical evidence for an asteroidal impact at late Devonian mass extinction horizon

Apr 1984

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984natur.308..629m&link_type=abstract

Nature (ISSN 0028-0836), vol. 308, April 12, 1984, p. 629-631. Research supported by the U.S. Department of Energy and Field Mus

Mathematics

Logic

13

Asteroids, Biological Evolution, Extinction, Geochemistry, Impact Damage, Anomalies, Iridium, Neutron Activation Analysis, Sediments, Stratigraphy

Scientific paper

Three sedimentary sequences in New York State (Dunkirk Beach, Walnut Creek Gorge, and Mills Mills) and one sedimentary sequence in Belgium (Sinsin), that cross the Devonian Frasnian-Famennian boundary, were examined for an iridium (Ir) anomaly to determine whether the biotic extinctions at the end of the Cretaceous could have been caused by an asteroidal impact. The sampling at three of the four areas was on 2-cm center points, and 15 to 20 g of sample were collected. The instrumental neutron activation method required 5 g samples, and consequently the distance between samples was less than 1 cm. Though the Devonian samples studied had a high probability of locating an Ir anomaly, none was found. The highest Ir values were between 0.2 and 2 percent of those reported for the marine and terrestrial Ir analyses at the Cretaceous-Tertiary boundary, and Devonian pyrite-rich sediments did not exhibit high Ir concentrations.

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