論文

査読有り
2016年5月1日

Tracking the redox history and nitrogen cycle in the pelagic Panthalassic deep ocean in the Middle Triassic to Early Jurassic: Insights from redox-sensitive elements and nitrogen isotopes

Palaeogeography, Palaeoclimatology, Palaeoecology
  • Wataru Fujisaki
  • ,
  • Yusuke Sawaki
  • ,
  • Shinji Yamamoto
  • ,
  • Tomohiko Sato
  • ,
  • Manabu Nishizawa
  • ,
  • Brian F. Windley
  • ,
  • Shigenori Maruyama

449
開始ページ
397
終了ページ
420
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1016/j.palaeo.2016.01.039
出版者・発行元
Elsevier B.V.

In order to clarify the redox history of the central Panthalassic Ocean in the Middle Triassic (Anisian) to Early Jurassic (Toarcian), we determined the abundances of major, trace and rare earth elements, and organic carbon and total nitrogen isotopes from well-exposed shales interbedded with deep-sea cherts from Inuyama, southwest Japan. A distinct positive Ce anomaly accompanying high Mn and weak Mo enrichments was detected in the transitional sequence across the Tr-J boundary, which indicates deposition under a more oxic condition than at any other period in the study section. The oxic period lasted for 130-170 kyr, and coincided with a faunal turnover at the end of the Triassic. On the other hand, strong enrichments of U, V, Mo, TOC and TN in Anisian and Toarcian black shales suggest deep ocean anoxia in both intervals. Highly concentrated Mo contents in some black shales indicate euxinia in the pelagic Panthalassic deep ocean. δ15NTN values are low, down to -2.0 ‰, in such black shales enriched in redox-sensitive elements, compared with other shales. This low δ15NTN values during recurrent oceanic euxinic events in the Anisian may indicate strong assimilation of ammonium, but the possibility of enhanced nitrogen fixation cannot be ruled out especially for the Toarcian anoxic event. This work provides the first documentation of the long-term redox history in the pelagic Panthalassic deep ocean, from the Middle Triassic to the Early Jurassic, based on redox-sensitive elements in shales, and it reveals probable links between oceanic redox changes and biological activity.

リンク情報
DOI
https://doi.org/10.1016/j.palaeo.2016.01.039
ID情報
  • DOI : 10.1016/j.palaeo.2016.01.039
  • ISSN : 0031-0182
  • SCOPUS ID : 84960172254

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