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Science 9 May 2003:
Vol. 300. no. 5621, pp. 961 - 964
DOI: 10.1126/science.1082182
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Reports

Sediment-Dispersed Extraterrestrial Chromite Traces a Major Asteroid Disruption Event

Birger Schmitz,1,2* Therese Häggström,2 Mario Tassinari2

Abundant extraterrestrial chromite grains from decomposed meteorites occur in middle Ordovician (480 million years ago) marine limestone over an area of ~250,000 square kilometers in southern Sweden. The chromite anomaly gives support for an increase of two orders of magnitude in the influx of meteorites to Earth during the mid-Ordovician, as previously indicated by fossil meteorites. Extraterrestrial chromite grains in mid-Ordovician limestone can be used to constrain in detail the temporal variations in flux of extraterrestrial matter after one of the largest asteroid disruption events in the asteroid belt in late solar-system history.

1 Department of Earth Science, Rice University, Post Office Box 1892, Houston, TX 77251, USA.
2 Marine Geology, Earth Sciences Center, Box 460, SE-40530 Göteborg, Sweden.

* To whom correspondence should be addressed. E-mail: birger{at}gvc.gu.se

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