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| Titel |
Campanian-Maastrichtian intermediate- to deep-water changes in the high latitudes: benthic foraminiferal evidence |
| VerfasserIn |
M. Koch, O. Friedrich |
| 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 |
250065247
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| Zusammenfassung |
| During the latest Cretaceous cooling phase, a positive shift in benthic foraminiferal
δ18O values lasting about 1.5 Ma (71.5-70 Ma) can be observed at a global scale
(Campanian-Maastrichtian Boundary Event, CMBE). This δ18O excursion is interpreted as
being influenced by a change in intermediate- to deep-water circulation or by temporal
build-up of Antarctic ice sheets. Here we test if benthic foraminiferal assemblages (BFA)
from a southern high-latitudinal site near Antarctica (Ocean Drilling Program Site 690, Maud
Rise, Weddell Sea, southern South Atlantic) are influenced by the CMBE. If the δ18O
transition reflects a change in intermediate- to deep-water circulation from low-latitude to
high-latitude water masses, this change would result in cooler temperatures, higher oxygen
concentration, and possibly lower organic-matter flux at the seafloor, resulting in a major
BFA change. If, however, the δ18O transition has mainly been triggered by ice
formation, no considerable compositional difference in BFA would be expected.
Our data show a separation of the studied succession into two parts with distinctly
different BFA. Species dominating the older part (73.0 to 70.5 Ma) tolerate less
bottom-water oxygenation (e.g. Paralabamina hillebrandti) and are typical components of
low-latitude assemblages (e.g. Reussella szajnochae). In contrast, the younger part
(70.0 to 68.0 Ma) is characterized by species that indicate well-oxygenated bottom
waters (e.g. Nuttallides truempyi) and species common in high-latitude assemblages
(Pullenia spp.). We interpret the observed change in BFA towards a well-oxygenated
environment to reflect the onset of a shift from low-latitude towards high-latitude
dominated intermediate- to deep-water sources. This implies that a change in oceanic
circulation rather than ice volume was at least a major component of the CMBE. |
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