Details
| Original language | English |
|---|---|
| Pages (from-to) | 315-318 |
| Number of pages | 4 |
| Journal | GEOLOGY |
| Volume | 38 |
| Issue number | 4 |
| Publication status | Published - Apr 2010 |
| Externally published | Yes |
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.
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In: GEOLOGY, Vol. 38, No. 4, 04.2010, p. 315-318.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Global enhancement of ocean anoxia during oceanic anoxic event 2
T2 - A quantitative approach using U isotopes
AU - Montoya-Pino, Carolina
AU - Weyer, Stefan
AU - Anbar, Ariel D.
AU - Pross, Jörg
AU - Oschmann, Wolfgang
AU - van de Schootbrugge, Bas
AU - Arz, Helge W.
PY - 2010/4
Y1 - 2010/4
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=77954002130&partnerID=8YFLogxK
U2 - 10.1130/G30652.1
DO - 10.1130/G30652.1
M3 - Article
AN - SCOPUS:77954002130
VL - 38
SP - 315
EP - 318
JO - GEOLOGY
JF - GEOLOGY
SN - 0091-7613
IS - 4
ER -