title: Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification.
abstract: The catastrophic disruption of the L chondrite parent body in the asteroid belt c. 470 Ma initiated a prolonged meteorite bombardment of Earth that started in the Ordovician and continues today. Abundant L chondrite meteorites in Middle Ordovician strata have been interpreted to be the consequence of the asteroid breakup event. Here we report a zircon U-Pb date of 467.50±0.28 Ma from a distinct bed within the meteorite-bearing interval of southern Sweden that, combined with published cosmic-ray exposure ages of co-occurring meteoritic material, provides a precise age for the L chondrite breakup at 468.0±0.3 Ma. The new zircon date requires significant revision of the Ordovician timescale that has implications for the understanding of the astrogeobiologic development during this period. It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated.
authors.affiliation: Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden.
authors.forename: A
authors.identifier: 0000-0001-7281-6840
authors.initials: A
authors.lastname: Lindskog
authors.affiliation: Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.|Centre for Star and Planet Formation, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.
authors.forename: M M
authors.initials: MM
authors.lastname: Costa
authors.affiliation: Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.|Center for Macroecology, Evolution and Climate, University of Copenhagen, Denmark.
authors.forename: C M Ø
authors.initials: CM
authors.lastname: Rasmussen
authors.affiliation: Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.|Centre for Star and Planet Formation, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.
authors.forename: J N
authors.initials: JN
authors.lastname: Connelly
authors.affiliation: Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden.
authors.forename: M E
authors.initials: ME
authors.lastname: Eriksson
mesh_terms: D044822:Biodiversity; D018534:Earth, Planet; D055593:Geological Phenomena; D019110:Meteoroids; D018543:Minor Planets; D055110:Radiometric Dating; D017640:Silicates / Q000032:analysis; D013548:Sweden; D013997:Time Factors; D015040:Zirconium / Q000032:analysis
chemical_list: D017640:Silicates; C003784:zircon; D015040:Zirconium