Global enhancement of ocean anoxia during oceanic anoxic event 2

A quantitative approach using U isotopes

Carolina Montoya-Pino, Stefan Weyer, Ariel D. Anbar, Jörg Pross, Wolfgang Oschmann, Bas van de Schootbrugge, Helge W. Arz

Research output: Contribution to journalArticle

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Abstract

During the Mesozoic greenhouse world, the oceans underwent several oceanic anoxic events (OAEs) characterized by intervals during which organic-rich black shales were deposited, indicating strong oxygen depletion in the marine realm. The Cenomanian-Turonian OAE2 (ca. 93 Ma) represents one of the most prominent events of the Cretaceous, with significant perturbations of the global carbon cycle. Although OAE2 likely reached a global scale, the spatial extent of seawater anoxia during this OAE is poorly constrained. Here we demonstrate that variations in the 238U/235U isotope ratio (δ238U), a newly developed paleoredox proxy, can be used to quantify the extent of marine anoxia. For black shales from the mid-Cretaceous OAE2 we find a systematic shift toward lighter δ238U and lower U concentrations as compared to modern equivalent organic-rich sediments from the Black Sea. This shift translates to a global increase of oceanic anoxia during OAE2 by at least a factor of three as compared to the present day or to periods before and after OAE2. The constant offset in U concentrations and isotope compositions of black shales throughout OAE2 compared to modern Black Sea sediments indicates an enhancement of oceanic anoxic conditions already prior to the onset of OAE2.

Original languageEnglish (US)
Pages (from-to)315-318
Number of pages4
JournalGeology
Volume38
Issue number4
DOIs
StatePublished - Apr 2010

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anoxia
isotope
ocean
Cretaceous
Turonian
carbon cycle
anoxic conditions
sediment
perturbation
seawater
oxygen
Black Sea

ASJC Scopus subject areas

  • Geology

Cite this

Montoya-Pino, C., Weyer, S., Anbar, A. D., Pross, J., Oschmann, W., van de Schootbrugge, B., & Arz, H. W. (2010). Global enhancement of ocean anoxia during oceanic anoxic event 2: A quantitative approach using U isotopes. Geology, 38(4), 315-318. https://doi.org/10.1130/G30652.1

Global enhancement of ocean anoxia during oceanic anoxic event 2 : A quantitative approach using U isotopes. / Montoya-Pino, Carolina; Weyer, Stefan; Anbar, Ariel D.; Pross, Jörg; Oschmann, Wolfgang; van de Schootbrugge, Bas; Arz, Helge W.

In: Geology, Vol. 38, No. 4, 04.2010, p. 315-318.

Research output: Contribution to journalArticle

Montoya-Pino, C, Weyer, S, Anbar, AD, Pross, J, Oschmann, W, van de Schootbrugge, B & Arz, HW 2010, 'Global enhancement of ocean anoxia during oceanic anoxic event 2: A quantitative approach using U isotopes', Geology, vol. 38, no. 4, pp. 315-318. https://doi.org/10.1130/G30652.1
Montoya-Pino, Carolina ; Weyer, Stefan ; Anbar, Ariel D. ; Pross, Jörg ; Oschmann, Wolfgang ; van de Schootbrugge, Bas ; Arz, Helge W. / Global enhancement of ocean anoxia during oceanic anoxic event 2 : A quantitative approach using U isotopes. In: Geology. 2010 ; Vol. 38, No. 4. pp. 315-318.
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