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

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

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)397-420
Number of pages24
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume449
DOIs
Publication statusPublished - May 1 2016
Externally publishedYes

Fingerprint

nitrogen cycle
nitrogen isotope
Anisian
Toarcian
isotopes
Triassic
Jurassic
oceans
history
ocean
nitrogen
rare earth elements
anoxia
nitrogen fixation
oxic conditions
deep sea
bioactive properties
hypoxia
assimilation (physiology)
turnover

Keywords

  • Japan
  • Mass extinction
  • Oceanic anoxic event
  • Sediment geochemistry
  • Shales

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Palaeontology
  • Earth-Surface Processes
  • Oceanography

Cite this

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. / Fujisaki, Wataru; Sawaki, Yusuke; Yamamoto, Shinji; Sato, Tomohiko; Nishizawa, Manabu; Windley, Brian F.; Maruyama, Shigenori.

In: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 449, 01.05.2016, p. 397-420.

Research output: Contribution to journalArticle

Fujisaki, Wataru ; Sawaki, Yusuke ; Yamamoto, Shinji ; Sato, Tomohiko ; Nishizawa, Manabu ; Windley, Brian F. ; Maruyama, Shigenori. / 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. In: Palaeogeography, Palaeoclimatology, Palaeoecology. 2016 ; Vol. 449. pp. 397-420.
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AU - Fujisaki, Wataru

AU - Sawaki, Yusuke

AU - Yamamoto, Shinji

AU - Sato, Tomohiko

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AU - Windley, Brian F.

AU - Maruyama, Shigenori

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AB - 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.

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