Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden.
Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.
Nat Commun. 2017 Jan 24;8:14066. doi: 10.1038/ncomms14066.
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.
约 470 万年前，L 型球粒陨石母体在小行星带的灾难性破裂，引发了一场持续至今的漫长的陨石撞击地球事件。中奥陶世地层中丰富的 L 型球粒陨石被解释为小行星解体事件的结果。在这里，我们报告了来自瑞典南部陨石层间一个明显层位的锆石 U-Pb 年龄为 467.50±0.28Ma，结合同时代陨石物质的已发表宇宙射线暴露年龄，为 L 型球粒陨石的破裂提供了一个精确的年龄，为 468.0±0.3Ma。新的锆石年龄需要对奥陶纪时间尺度进行重大修正，这对理解这一时期的天体生物学发展具有重要意义。有人认为，中奥陶世的陨石撞击在大奥陶纪生物多样性事件中发挥了关键作用，但这项研究表明，这两个现象并无关联。
