2024-12-17 ノースウェスタン大学
＜関連情報＞
- https://news.northwestern.edu/stories/2024/12/prehistoric-rock-in-japan-reveals-clues-to-major-ocean-anoxic-event/
- https://www.science.org/doi/10.1126/sciadv.adn8365
海洋貧酸素現象1aの放射性同位体年代： 駆動メカニズム解析の枠組み Radioisotopic chronology of Ocean Anoxic Event 1a: Framework for analysis of driving mechanisms
Youjuan Li, Brad S. Singer, Reishi Takashima, Mark D. Schmitz, […], and Katarina Savatic
Science Advances Published:20 Nov 2024
DOI:https://doi.org/10.1126/sciadv.adn8365
Abstract
The timing, tempo, and causative mechanisms of Ocean Anoxic Event 1a (OAE1a), one of several such abrupt perturbations of the Mesozoic global carbon cycle, remain uncertain. Mudstones interbedded with tuffs in Hokkaido, Japan preserve carbon and osmium isotope shifts recording OAE1a. U-Pb zircon ages of tuffs constrain the OAE1a onset to 119.55 +0.072/−0.079 million years ago (Ma) and its duration to 1116 +87/−93 thousand years (kyr). Isotopic excursions of osmium followed by carbon that mark the rapid onset of OAE1a each lasted ~115 kyr. Critically, the occurrence of index fossil Leupoldina cabri in the Hokkaido OAE1a section, which also caps and thus postdate Ontong Java Plateau (OJP) basalts, has a U-Pb zircon age of ~118.7 to 118.4 Ma. Therefore, OJP volcanism remains a probable source of unradiogenic osmium and light carbon and a causative mechanism of OAE1a.
