Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2

Xiaoli Zhou, Hugh C. Jenkyns, Jeremy D. Owens, Christopher K. Junium, Xin Yuan Zheng, Bradley B. Sageman, Dalton S. Hardisty, Timothy W. Lyons, Andy Ridgwell, Zunli Lu

Research output: Research - peer-reviewArticle

  • 12 Citations

Abstract

Global warming lowers the solubility of gases in the ocean and drives an enhanced hydrological cycle with increased nutrient loads delivered to the oceans, leading to increases in organic production, the degradation of which causes a further decrease in dissolved oxygen. In extreme cases in the geological past, this trajectory has led to catastrophic marine oxygen depletion during the so-called oceanic anoxic events (OAEs). How the water column oscillated between generally oxic conditions and local/global anoxia remains a challenging question, exacerbated by a lack of sensitive redox proxies, especially for the suboxic window. To address this problem, we use bulk carbonate I/Ca to reconstruct subtle redox changes in the upper ocean water column at seven sites recording the Cretaceous OAE 2. In general, I/Ca ratios were relatively low preceding and during the OAE interval, indicating deep suboxic or anoxic waters exchanging directly with near-surface waters. However, individual sites display a wide range of initial values and excursions in I/Ca through the OAE interval, reflecting the importance of local controls and suggesting a high spatial variability in redox state. Both I/Ca and an Earth System Model suggest that the northeast proto-Atlantic had notably higher oxygen levels in the upper water column than the rest of the North Atlantic, indicating that anoxia was not global during OAE 2 and that important regional differences in redox conditions existed. A lack of correlation with calcium, lithium, and carbon isotope records suggests that neither enhanced global weathering nor carbon burial was a dominant control on the I/Ca proxy during OAE 2.

LanguageEnglish (US)
Pages510-526
Number of pages17
JournalPaleoceanography
Volume30
Issue number5
DOIs
StatePublished - May 1 2015

Fingerprint

oxygenation
Turonian
upper ocean
water column
anoxia
oxygen
ocean
redox conditions
hydrological cycle
lithium
oxic conditions
carbon isotope
global warming
dissolved oxygen
solubility
weathering
calcium
trajectory
Cretaceous
surface water

Keywords

  • I/Ca
  • OAE 2
  • oxygenation

ASJC Scopus subject areas

  • Oceanography
  • Palaeontology

Cite this

Zhou, X., Jenkyns, H. C., Owens, J. D., Junium, C. K., Zheng, X. Y., Sageman, B. B., ... Lu, Z. (2015). Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2. Paleoceanography, 30(5), 510-526. DOI: 10.1002/2014PA002741

Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2. / Zhou, Xiaoli; Jenkyns, Hugh C.; Owens, Jeremy D.; Junium, Christopher K.; Zheng, Xin Yuan; Sageman, Bradley B.; Hardisty, Dalton S.; Lyons, Timothy W.; Ridgwell, Andy; Lu, Zunli.

In: Paleoceanography, Vol. 30, No. 5, 01.05.2015, p. 510-526.

Research output: Research - peer-reviewArticle

Zhou, X, Jenkyns, HC, Owens, JD, Junium, CK, Zheng, XY, Sageman, BB, Hardisty, DS, Lyons, TW, Ridgwell, A & Lu, Z 2015, 'Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2' Paleoceanography, vol 30, no. 5, pp. 510-526. DOI: 10.1002/2014PA002741
Zhou X, Jenkyns HC, Owens JD, Junium CK, Zheng XY, Sageman BB et al. Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2. Paleoceanography. 2015 May 1;30(5):510-526. Available from, DOI: 10.1002/2014PA002741
Zhou, Xiaoli ; Jenkyns, Hugh C. ; Owens, Jeremy D. ; Junium, Christopher K. ; Zheng, Xin Yuan ; Sageman, Bradley B. ; Hardisty, Dalton S. ; Lyons, Timothy W. ; Ridgwell, Andy ; Lu, Zunli. / Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian-Turonian OAE 2. In: Paleoceanography. 2015 ; Vol. 30, No. 5. pp. 510-526
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