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| Titel |
Evolution of neodymium isotopic signature of seawater on the northwest Pacific margin: new insights on oceanic circulation changes during the Late Cretaceous |
| VerfasserIn |
M. Moiroud, E. Pucéat, Y. Donnadieu, G. Bayon, K. Moriya, J.-F. Deconinck |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069113
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| Zusammenfassung |
| Changes in oceanic circulation during the Late Cretaceous have been inferred from the neodymium isotopic signature (εNd) of fish remains, which reflects that of past seawater (Robinson et al., 2010; MacLeod et al., 2011). Yet the nature of these changes remains controversial, mainly due to insufficient temporal and spatial coverage of Nd isotope data. More specifically, data from continental margins remain scarce for the Cretaceous (Soudry et al., 2006). Yet such records would help to discuss the origin of the changes depicted in the deep and intermediate water records (changes in the location of deep water production vs. changes in the composition of water in the source area).
This work aims at reconstructing the evolution of surface water εNd during the Late Cretaceous in a potential area of deep water sinking (Frank et al., 2005), the north Pacific. For this purpose, samples of fish remains have been recovered from sediments from Hokkaidō (northern Japan; Takashima et al., 2004) and analysed for their εNd. Preliminary results display rather radiogenic values, which decrease from -1 ε-unit at the end of the Turonian to -3 ε-units during the Santonian. This evolution may reflect changes in the isotopic signature of the eroded sediments on the northwestern Pacific margin and/or changes in surface current organization in the Pacific. Similar trends have been reported in contemporaneous sediments from the northern Tethyan margin (Pucéat et al., 2005) and from south Atlantic ODP samples (Robinson et al., 2010). This relationship might indicate a contribution of Pacific surface waters to Tethyan surface waters and Southern Ocean intermediate/deep waters. Nevertheless further analyses from additional continental margins are required to support these hypotheses.
References:
Frank, T.D., Thomas, D.J., Leckie, R.M., Arthur, M.A., Bown, P.R., Jones, K., and Lees, J.A., 2005. The Maastrichtian record from Shatsky Rise (northwest Pacific): A tropical perspective on global ecological and oceanographic changes, Paleoceanography 20, PA1008, doi:10.1029/2004PA001052
MacLeod, K.G., Londoño, C.I., Martin, E.E., Jiménez Berrosco, Á. and Basak, C., 2011. Changes in North Atlantic circulation at the end of the Cretaceous greenhouse interval. Nature Geoscience 4, 779–782.
Robinson, A., Murphy, D.P., Vance, D., and Thomas, D.J., 2010. Formation of “Southern Component Water” in the Late Cretaceous: evidence from Nd-isotopes. Geological Society of America 38 (10), 871–874
Soudry, D., Glenn, C.R., Nathan, Y., Segal, I., and VonderHaar, D.L., 2006. Evolution of Tethyan phosphogenesis along the northern edges of the Arabian-African shield during the Cretaceous-Eocene as deduced from temporal variations of Ca and Nd isotopes and rates of P accumulation. Earth-Science Reviews 78, 27–57
Takashima, R., Kawabe, F., Nishi, H., Moriya, K., Wani, R., and Ando, H., 2004. Geology and stratigraphy of forearc basin sediments in Hokkaidō, Japan: Cretaceous environmental events on the north-west Pacific margin. Cretaceous research 25, 365–390
Thomas, D.J., 2004. Evidence for Production of North Pacific Deep Waters During the early Cenozoic Greenhouse. Nature 430, 65–68. |
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