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Titel |
Plio-Pleistocene evolution of water mass exchange and erosional input in the Fram Strait |
VerfasserIn |
Claudia Teschner, Martin Frank, Brian Alexander Haley |
Konferenz |
EGU General Assembly 2011
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 13 (2011) |
Datensatznummer |
250048575
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Zusammenfassung |
We determined the isotopic composition of neodymium (Nd) and lead (Pb) of past seawater
to reconstruct water mass exchange and erosional input between the Arctic Ocean and the
Norwegian-Greenland Seas over the past 5 Ma. For this purpose, sediments of ODP site 911
(leg 151) located at 900 m water depth on the Yermak Plateau in the Fram Strait were
used. The paleo-seawater variability of Nd and Pb isotopes was extracted from the
sea water-derived metal oxide coatings on the sediment particles following the
leaching method of Gutjahr et al. (2007). All radiogenic isotope data were acquired by
Multi-Collector (MC) ICP-MS. The site 911 stratigraphy of Knies et al. (2009) was
applied.
Surface sediment Sr and Nd isotope data, as well as downcore Sr isotope data obtained on the
same leaches are close to seawater and confirm the seawater origin of the Nd and Pb isotope
signatures. The deep water Nd isotope time series extracted from site 911 was in general
more radiogenic (ÉNd = -7.5 to -10) than present day deep water (ÉNd = -9.8 to -11.8) in the
area of the Fram Strait (Andersson et al., 2008) and does not show a systematic
trend with time. In contrast, the radiogenic isotope composition of Pb evolved from
206Pb/204Pb ratios around 18.7 to more radiogenic values around 19.2 between 2 Ma and
today.
The data indicate that mixing of water masses from the Arctic Ocean and the
Norwegian-Greenland Seas has controlled the Nd isotope signatures of deep waters on the
Yermak Plateau over the past 5 Ma. Prior to 1.7 Ma the Nd isotope signatures on
the Yermak Plateau were less radiogenic than waters from the same depth in the
central Arctic Ocean (Haley et al., 2008) pointing to a greater influence from the
Norwegian-Greenland Seas. After 1.7 Ma the central Arctic and Yermak Plateau data
have varied around similar values indicating water mass mixing overall similar to
today.
In contrast, the Pb isotope composition of deep waters in the Fram Strait appears to have been
dominated by weathering inputs from glacially weathering old continental landmasses, such
as Greenland or parts of Svalbard since 2 Ma. A similar control over the Pb isotope evolution
of seawater since the onset of Northern Hemisphere Glaciation was recorded by
ferromanganese crusts that grew from North Atlantic Deep Water in the western North
Atlantic.
References:
Gutjahr, M., Frank, M., Stirling, C.H., Klemm, V., van de Flierdt, T. and Halliday, A.N.
(2007): Reliable extraction of a deepwater trace metal isotope signal from Fe-Mn
oxyhydroxide coatings of marine sediments.- Chemical Geology 242, 351-370
Haley B. A., M. Frank, R.F. Spielhagen and A. Eisenhauer (2008): Influence of brine
formation on Arctic Ocean circulation over the past 15 million years. Nature Geoscience 1,
68–72
Andersson, P.S., Porcelli, D., Frank, M., Björk, G., Dahlqvist, R. and Gustafsson, Ö. (2008):
Neodymium isotopes in seawater from the Barents Sea and Fram Strait Arctic-Atlantic
gateways.- Geochim. Cosmochim. Acta 72, 2854-2867
Knies, J., J. Matthiessen, C. Vogt, J.S. Laberg, B.O. Hjelstuen, M.Smelror, E. Larsen, K.
Andreassen, T. Eidvin and T.O. Vorren (2009): The Plio-Pleistocene glaciation of the Barents
Sea–Svalbard region: a new model based on revised chronostratigraphy - Quaternary Science
Reviews 28, 9-10, 812-829 |
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