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TitleDeep-sea record of impact apparently unrelated to mass extinction in the Late Triassic
AuthorOnoue, T; Sato, H; Nakamura, T; Noguchi, T; Hidaka, Y; Shirai, N; Ebihara, M; Osawa, T; Hatsukawa, Y; Toh, Y; Koizumi, M; Harada, H; Orchard, M JORCID logo; Nedachi, M
SourceProceedings of the National Academy of Sciences of the United States of America vol. 109, no. 47, 2012 p. 19134-19139, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20120388
PublisherProceedings of the National Academy of Sciences
Mediapaper; on-line; digital
File formatpdf
Subjectspaleontology; extraterrestrial geology; meteorite craters; meteorites; extinctions, biotic; biostratigraphy; Triassic; Mesozoic
Illustrationslocation maps; photomicrographs; plots
ProgramGEM: Geo-mapping for Energy and Minerals Yukon Sedimentary Basins
Released2012 11 05
AbstractThe 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm.

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