Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic

Onoue, Tetsuji*; Sato, Honami*; Nakamura, Tomoki*; Noguchi, Takaaki*; Hidaka, Yoshihiro*; Shirai, Naoki*; Ebihara, Mitsuru*; Osawa, Takahito; Hatsukawa, Yuichi; Toh, Yosuke; et al.

Proceedings of the National Academy of Sciences of the United States of America, 109(47), p.19134 - 19139, 2012/11

https://doi.org/10.1073/pnas.1209486109

The 34 million year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. As with the Chicxulub impact event at the Cretaceous/Paleogene boudary, the Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., the Triassic/Jurassic boundary). However, the causal link between these impact events and a mass extinction event in the Late Triassic remains controversial because of a lack of stratigraphic records of their ejecta deposits. Here we report evidence for an impact event (platinum group elements anomaly, nickel-rich magnetite and microspherules) deposited within a Paleo-Pacific basin in 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 anomaly may be found on a global scale. The middle Norian age of the ejecta deposit suggests that the impact event that produced the 100-km-wide Manicouagan crater in Canada8 is most likely related to its deposition. Our analysis of siliceous microfossils shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine fossils. However, such an event has been reported among terrestrial tetrapods and floras in North America. We therefore hypothesize that the Manicouagan impact caused the catastrophic collapse of terrestrial ecosystems near the impact site, but not within the marine realm.

Technological development of bent test subassembly retrieval device in the experimental fast reactor Joyo

Ashida, Takashi; Okazaki, Yoshihiro; Miyamoto, Kazuyuki; Noguchi, Koichi; Ito, Hideaki

no journal, , 

The 15th periodic inspection of Joyo commenced in May 2007 with the Fuel Handling Machine (FHM) being set up on the Rotating Plug (R/P) for refueling in June. When the R/P was taken down, measuring the load of the Hold-Down Shaft (HDS) revealed an abnormal decrease above the in-vessel storage rack (IVS). As a result of the observations, it was discovered that the top of the irradiation test S/A "MARICO-2"had bent onto the IVS as an obstacle, and had damaged the Upper Core Structure (UCS). The other action items in the restoration work, which are design of UCS and MARICO-2 handling device will be investigated in detail designs. The experience obtained through the restoration work in Joyo will provided valuable insights into possible further improvements and verifications for in-vessel inspection and repair techniques in SFRs.

Thermodynamic calculation on chemical forms of in-vessel debris of Fukushima-Daiichi NPP

Ikeuchi, Hirotomo; Yano, Kimihiko; Kaji, Naoya; Washiya, Tadahiro; Kondo, Yoshikazu*; Noguchi, Yoshihiro*

no journal, , 

no abstracts in English

Chemical form estimation of in-vessel fuel debris by thermodynamic calculation with melt progression analysis

Ikeuchi, Hirotomo; Noguchi, Yoshihiro*; Kondo, Yoshikazu*; Yano, Kimihiko; Kaji, Naoya; Washiya, Tadahiro

no journal, ,