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| Titel |
Malformations in Discoaster species related to the PETM and ELMO hyperthermal events |
| VerfasserIn |
I. Raffi, B. De Bernardi, C. Agnini |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023821
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| Zusammenfassung |
| Several studies, focused on calcareous nannofossil assemblages at the Paleocene/Eocene
transition (e.g., Bralower, 2002; Raffi et al., 2005; Gibbs et al., 2006; 2007; Agnini et al,
2007; Mutterlose et al., 2007), have evidenced changes and turnovers, some of them
occurring on global scale. These features seem to be related to dramatic changes in
environmental conditions during the well-known Paleocene-Eocene Thermal Maximum
(PETM). The PETM was a period of extreme, transient global warming interpreted as
possible consequence of a massive release of light carbon in the ocean-atmosphere system.
This rapid injection of 13C-depleted carbon into the geo-biosphere results in a remarkable
increase of CO2 levels that, in turn, caused significant changes in the chemical and physical
proprieties of oceanic waters which profoundly influenced productivity and biogenic
sedimentation.
The PETM affected biogeochemical cycles and ecosystems, including significant biotic
turnovers observed in terrestrial and marine realms. In particular , calcareous nannofossil
assemblages is characterized by the occurrence of transient excursion taxa, which include
Rhomboaster calcitrapa group and peculiar forms of asymmetrical discoasterids
ascribed to species Discoaster araneus and D. anartios. This unusual assemblage is
restricted to the carbon isotope excursion (CIE) of the PETM, as documented in all
the known PETM reference sections studied so far. Moreover, a detailed study of
ODP Site 1263 (Walvis Ridge) showed that Discoaster specimens are consistently
affected by malformations both during the PETM and the ELMO hyperthermal
events (Raffi and De Bernardi, 2008). These findings have been interpreted as a
possible result of the chemical stressed water conditions linked to the anomalous CO2
levels during the CIE-PETM interval (Agnini et al., 2006). This study documents
that malformed Discoaster specimens are consistently present in other subtropical
Atlantic Ocean sections (ODP Sites 1262 and1265) and in the Tethyan domain (Italy)
concomitantly with PETM and ELMO events. These data suggest a wide biogeographic
distribution for the deformed short-lived discoasterids, and document similar biotic
characteristics between the ELMO horizon and Paleocene-Eocene thermal maximum. |
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