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| Titel |
Impact of paleoceanographic changes at glacial/interglacial transitions on benthic foraminiferal faunas of the eastern North Atlantic (IODP Expedition 339, Site U1385) |
| VerfasserIn |
Patrick Grunert, David Hodell, Carlos Alvarez Zarikian, F. Javier Hernández-Molina, D. A. V. Stow |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093048
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| Publikation (Nr.) |
 EGU/EGU2014-7418.pdf |
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| Zusammenfassung |
| Communities of deep-sea foraminifera are sensitive recorders of environmental conditions.
Consequently, the actualistic interpretation of fossil foraminiferal assemblages has become a
valuable tool for the reconstruction of paleoceanographic conditions at the sea-floor. For the
present study, a quantitative data-set of benthic foraminifera >125μm from the eastern North
Atlantic has been analysed to understand paleoceanographic changes (AMOC, ventilation,
productivity) associated with glacial/interglacial transitions in more detail. The data-set
consists of a series of samples from IODP Site U1385 spanning Terminations I, II and IV and
several short-term (millennial-scale) climatic events including the Younger Dryas (YD),
Heinrich (H) 1, and H 11.
On the family and generic levels, a characteristic succession of foraminiferal assemblages can
be recognized at all studied glacial/interglacial transitions: a glacial fauna with abundant
occurrences of cassidulinids (Cassidulina, Globocassidulina); a fauna characterized by high
abundances of buliminds (Bulimina, Globobulimina) and/or bolivinellids (Bolivinita) that is
associated with H-events and the beginning of each termination; a fauna with high
abundances of miliolids (mainly Pyrgo) and cibicidids at the end of the termination; an
interglacial fauna composed of buliminds (Bulimina), gavellinellids (Gyroidinoides), and
pseudoparrellids (Epistominella). For the glacial and interglacial endmembers, this
succession indicates a moderately oxygenated environment at the seafloor with mesotrophic
conditions due to moderate export productivity. For the early phase of the terminations as
well as the short-term events, the dominance of infaunal taxa and high abundances of deep
infaunal taxa indicate an environment with high export productivity that is mainly controlled
by oxygen. Conversely, the absence of these taxa and the presence of miliolids suggests
well-ventilated environments and decreasing export productivity during the later phase of the
terminations.
While the evaluation on the generic level indicates repetitive paleoenvironmental changes for
the studied transitions, the taxonomic analysis on the species level reveals significant
differences between the terminations. These differences primarily concern the H-events and
the early phase of the terminations. H 1 differs from other such events by showing the highest
abundances of deep infaunal like Globobulimina affinis. In contrast, H 11 is characterized by
high abundances of Bulimina marginata and Cassidulina laevigata/teretis which are
rare to absent during H 1. A similar pattern is observed for a H-event associated
with the onset of Termination IV. In contrast, the H-event preceding Termination
IV shows high abundances of Bolivinita quadrilatera, a species absent all other
samples.
The explanation of the faunal differences between the terminations despite a rather
comparable environmental framework (poor ventilation and/or high export productivity)
indicates that the nature of short-term events is fairly diverse and an individual perspective
has to be put on each these events. E.g., in the case of H 1, increased primary productivity
and/or severely reduced AMOC compared to other such events might provide explanations.
For the other, less well known events new isotopic results are expected to help with the
explanation. |
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