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| Titel |
Late Campanian to Maastrichtian palaeoceanographic changes in the tropical Pacific |
| VerfasserIn |
C. Jung, S. Voigt, O. Friedrich, M. Frank |
| 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 |
250065221
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| Zusammenfassung |
| The Late Cretaceous was a period of long-term climate cooling succeeding the extreme
warmth of the mid-Cretaceous greenhouse world. The cooling is mainly considered as a
result of changes in ocean circulation due to plate-tectonic movements resulting in a
progressive deep-water exchange between the deep oceanic basins and a parallel drop
in pCO2 concentrations. The aim of this project is the reconstruction of changes
in surface hydrography, ocean circulation and deep-water sources in the tropical
Pacific (Shatsky Rise) using stable (C, O) and radiogenic isotopes (Nd) relative to the
Campanian-Maastrichtian Boundary Event (CMBE). We generated a high-resolution
benthic (bottom-water signal) foraminiferal stable isotope record from Nuttallides
truempyi and a planktic (surface-water signal) foraminiferal stable isotope record from
Rugoglobigerina rugosa for ODP Hole 1210B (Shatsky Rise). Oxygen isotopes are
measured to reconstruct changes in surface- and deep-water temperatures, although the
preservation of foraminiferal tests is not sufficient to calculate absolute temperatures.
Results show a positive excursion of benthic δ18O values that indicates beginning
bottom-water cooling during the CMBE and a temperature minimum after the event. The
planktic δ18O record shows constant temperatures during and after the CMBE. This
decoupling of bottom– and surface-water δ18O changes during the CMBE provides a
strong argument that possible buildups of ephemeral ice sheets in Antarctica are too
small to modify the oxygen isotopic composition of seawater. To decipher related
changes in ocean circulation and source regions of deep- to intermediate-water
masses, a high-resolution ÉNd record from the tropical Pacific was generated from
ferromanganese sediment coatings. Nd isotope data show a negative shift during the earliest
Maastrichtian, lasting ~3 Ma. This negative shift suggests a significant change in
intermediate-water masses at Shatsky Rise, changing from a dominant North Pacific source
gradually towards a water mass more affected by a Southern Ocean source region. |
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