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| Titel |
Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition |
| VerfasserIn |
K. Tachikawa, L. Vidal, M. Cornuault, M. García, A. Pothin, C. Sonzogni, E. Bard, G. Ménot, M. Revel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 6 ; Nr. 11, no. 6 (2015-06-11), S.855-867 |
| Datensatznummer |
250117318
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| Publikation (Nr.) |
 copernicus.org/cp-11-855-2015.pdf |
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| Zusammenfassung |
| Holocene eastern Mediterranean Sea sediments contain an organic-rich sapropel
S1 layer that was formed in oxygen-depleted waters. The spatial distribution
of this layer revealed that during S1 deposition, deep waters were anoxic
below a depth of 1800 m. However, whether this boundary permanently existed
from the early to the mid-Holocene has not been examined yet. To answer this
question, a multi-proxy approach was applied to a core retrieved close to the
1800 m boundary (at 1780 m). We measured the bulk sediment elemental
composition, the stable isotopic composition of the planktonic foraminifer
Globigerinoides ruber and the abundance of benthic foraminifera
since the last deglaciation. The result indicates that authigenic U and Mo
accumulation began around 13–12 cal ka BP, in concert with surface water
freshening estimated from the G. ruber δ18O record. The
onset of bottom and pore water oxygen depletion occurred prior to S1
deposition inferred from barium enrichment. In the middle of the S1
deposition period, reduced authigenic V, Fe and As contents and the
Br/Cl ratio indicated short-term bottom-water re-oxygenation. A sharp
Mn peak and maximal abundance for benthic foraminifera marked a total
recovery for circulation at approximately 7 cal ka BP. Based on our
results and existing data, we suggest that S1 formation within the upper
1780 m of the eastern Mediterranean Sea was preconditioned by reduced
ventilation, resulting from excess freshwater inputs due to insolation
changes under deglacial conditions that initiated between 15 and
12 cal ka BP within the upper
1780 m. Short-term re-oxygenation in the Levantine Basin is estimated to
have affected bottom water at least as deep as 1780 m in response to cooling
and/or the reduction of freshwater inputs. We tentatively propose that
complete ventilation recovery at the S1 termination was depth-dependent, with
earlier oxygenation within the upper 1780 m. Our results provide new
constraints on vertical water column structure in the eastern Mediterranean
Sea since the last deglaciation. |
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