An extraterrestrial trigger for the mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body
Birger Schmitz1*, Kenneth A. Farley2, Steven Goderis3, Philipp R. Heck4,5, Stig M. Bergström6, Samuele Boschi1, Philippe Claeys7, Vinciane Debaille8, Andrei Dronov9,10, Matthias van Ginneken11, David A.T. Harper12, Faisal Iqbal1, Johan Friberg1, Shiyong Liao13,14, Ellinor Martin1, Matthias M. M. Meier15,16, Bernhard Peucker-Ehrenbrink17, Bastien Soens7, Rainer Wieler15, Fredrik Terfelt1
1Astrogeobiology Laboratory, Department of Physics, Lund University, Lund, Sweden.2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA. 3Department of Chemistry, Vrije Universiteit Brussel, Brussels, Belgium. 4Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL, USA. 5Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, USA. 6School of Earth Sciences, The Ohio State University, Columbus, OH, USA. 7Analytical, Environmental, and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium. 8Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium. 9Geological Institute, Russian Academy of Sciences, Moscow, Russia. 10Institute of Geology and Oil and Gas Technologies, Kazan (Volga Region) Federal University, Kazan, Russia. 11Royal Belgian Institute of Natural Sciences, Brussels, Belgium. 12Department of Earth Sciences, Durham University, Durham, UK. 13Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China. 14CAS Center for Excellence in Comparative Planetology, Hefei, China. 15Department of Earth Sciences, ETH Zürich, Zürich, Switzerland. 16Naturmuseum St. Gallen, St. Gallen, Switzerland. 17Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
The breakup of the L-chondrite parent body in the asteroid belt 466 million years (Ma) ago still delivers almost a third of all meteorites falling on Earth. Our new extraterrestrial chromite and 3He data for Ordovician sediments show that the breakup took place just at the onset of a major, eustatic sea level fall previously attributed to an Ordovician ice age. Shortly after the breakup, the flux to Earth of the most fine-grained, extraterrestrial material increased by three to four orders of magnitude. In the present stratosphere, extraterrestrial dust represents 1% of all the dust and has no climatic significance. Extraordinary amounts of dust in the entire inner solar system during >2 Ma following the L-chondrite breakup cooled Earth and triggered Ordovician icehouse conditions, sea level fall, and major faunal turnovers related to the Great Ordovician Biodiversification Event.