奥陶纪
地质学
锆石
显生宙
古生物学
古生代
辐射定年
生物地层学
生物集群灭绝
牙形刺
地球科学
新生代
构造盆地
生物扩散
人口
人口学
社会学
作者
Bryan Sell,Leho Ainsaar,Stephen A. Leslie
摘要
Two of the largest known eruptions in the Phanerozoic produced the Ordovician Millbrig K-bentonite of North America and the Kinnekulle K-bentonite of Scandinavia, which have been previously suggested to be coeval. The Millbrig K-bentonite from Kentucky, USA and the Kinnekulle K-bentonite from Bornholm, Denmark yielded chemical abrasion thermal ionization mass spectrometry U–Pb zircon dates of 452.86 ± 0.29 and 454.41 ± 0.17 Ma (2σ analytical uncertainty), respectively, thus showing significant age differences contrary to what is generally held. These data and four additional newly dated K-bentonites directly establish the first radioisotopic age constraints for the Ordovician Katian–Sandbian global stage boundary, refine global stratigraphic correlations, date associated chemostratigraphic events, and suggest an alternative volcanic–climate hypothesis for the Late Ordovician. Supplementary material: U–Pb radioisotopic data table and analytical methods are available at www.geolsoc.org.uk/SUP18636 .
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