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| Titel |
U-series vs 14C ages of deep-sea corals from the southern Labrador Sea: Sporadic development of corals and geochemical processes hampering estimation of ambient water ventilation ages |
| VerfasserIn |
Claude Hillaire-Marcel, Jenny Maccali, Lucie Ménabréaz, Bassam Ghaleb, Aurélien Blénet, Evan Edinger |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145209
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| Publikation (Nr.) |
 EGU/EGU2017-9126.pdf |
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| Zusammenfassung |
| Deep-sea scleractinian corals were collected with the remotely operated ROPOS vehicle off
Newfounland. Fossil specimens of Desmophyllum dianthus were raised from coral
graveyards at Orphan Knoll (∼1700m depth) and Flemish cap (∼2200 m depth), while live
specimens were collected directly in overlying steep rock slopes. D. dianthus has an
aragonitic skeleton and is thus particularly suited for U-Th dating. We obtained > 70 U-series
ages along with > 20 14C measurements. Results display a discrete age distribution with two
age clusters: a Bølling-Allerød and Holocene cluster with > 20 samples, and a Marine
Isotope Stage (MIS) 5c cluster with ∼50 samples. Only two samples lay outside these
clusters, at ∼ 64 ka and at ∼181 ka. Contrary to the New England seamounts where coral
presence seems to have been continue through the last 70 ka, Orphan Knoll and
Flemish Cap graveyards are marked by the absence of preserved specimens from MIS
2 to MIS 4 and throughout MIS 6. For filter-feeding deep-sea corals, access to
food-rich waters is essential. Hence the Holocene and MIS 5 clusters observed in the
Labrador basin might represent intervals linked to high food availability, either
through production in the overlying water column, more effectively in relation to
particulate and dissolved organic carbon transport via an active Western Boundary
Undercurrent. Comparison of 230Th-ages vs 14C-ages in order to document changes in
ventilation ages of the ambient water masses is equivocal due to the presence of some
diagenetic and/or initial 230Th-excess. In addition, discrete diagenetic U-fluxes can be
documented from 234U/238U vs 230Th/238U data. They point to a recent winnowing of
sediment overlying the fossil corals that we link to the Holocene intensification of
the Western Boundary Undercurrent, which resulted in driving Fe-Mn coatings. |
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