Letter abstract
Nature Geoscience 1, 49 - 53 (2008)
Published online: 16 December 2007 | doi:10.1038/ngeo.2007.37
Subject Categories: Palaeontology | Geochemistry
Asteroid breakup linked to the Great Ordovician Biodiversification Event
Birger Schmitz1, David A. T. Harper2, Bernhard Peucker-Ehrenbrink3, Svend Stouge2, Carl Alwmark1, Anders Cronholm1, Stig M. Bergström4, Mario Tassinari1 & Wang Xiaofeng5
The rise and diversification of shelled invertebrate life in the early Phanerozoic eon occurred in two major stages. During the first stage (termed as the Cambrian explosion), a large number of new phyla appeared over a short time interval 
540 Myr ago. Biodiversity at the family, genus and species level, however, remained low until the second stage marked by the Great Ordovician Biodiversification Event in the Middle Ordovician period1, 2, 3. Although this event represents the most intense phase of species radiation during the Palaeozoic era and led to irreversible changes in the biological make-up of Earth's seafloors, the causes of this event remain elusive. Here, we show that the onset of the major phase of biodiversification 470 Myr ago coincides with the disruption in the asteroid belt of the L-chondrite parent body—the largest documented asteroid breakup event during the past few billion years4, 5. The precise coincidence between these two events is established by bed-by-bed records of extraterrestrial chromite, osmium isotopes and invertebrate fossils in Middle Ordovician strata in Baltoscandia and China. We argue that frequent impacts on Earth of kilometre-sized asteroids—supported by abundant Middle Ordovician fossil meteorites and impact craters6—accelerated the biodiversification process.
- Department of Geology, University of Lund, Sölvegatan 12, SE-22362 Lund, Sweden
- Natural History Museum of Denmark, Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS 25, Woods Hole, Massachusetts 02543, USA
- School of Earth Sciences, The Ohio State University, 125 South Oval Mall, Columbus, Ohio 43210, USA
- Yichang Institute of Geology and Mineral Resources, Yichang, Hubei 443003, China
Correspondence to: Birger Schmitz1 e-mail: birger.schmitz@geol.lu.se
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