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| Titel |
The onset of major Antarctic glaciation and the Eocene - Oligocene transition - a story of ice, temperature and sea level |
| VerfasserIn |
Alexander J. P. Houben, Stefan Schouten, Steven M. Bohaty, Bridget S. Wade, Mark Pagani, Stephen Galagher, Gert-Jan Reichart, Willemijn Quaijtaal, Appy Sluijs, Henk Brinkhuis |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035726
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| Zusammenfassung |
| The Eocene – Oligocene transition (EOT, ~33,5 Ma,) represents the final transformation of
the Eocene Greenhouse into an Icehouse world. It is now widely acknowledged
that cooling and/or ice-volume increases occurred stepwise, since high-resolution
foraminiferal oxygen isotope (δ18O)-records show a two step increase across the EOT,
separated about 200 kyr. Yet, it is still poorly defined how temperature decreased either
as a cause of or in consequence of ice volume increase, as δ18O-records capture
both effects. In the last decade, the development of molecular organic geochemical
“paleothermometers” like the alkenone unsaturation index (Uk’37) and the archaeal
membrane lipid based TEX86 proxy, provided alternative approaches to reconstruct
past temperatures. We generated sea surface temperature records from Deep Sea
Drilling Program (DSDP) Sites 511 & 512 in the Southwest Atlantic Ocean and
Site 336 from the Norwegian Greenland Sea using the U37K’ and TEX86 proxies
and integrate these records with foraminiferal δ18O measurements. Remains of
surface dwelling dinoflagellates (i.e. their cysts) have proven to sensitively record
changes in surface water conditions, i.e. temperature, salinity, productivity and
sea-ice cover. We interpreted changes in dinocyst assemblages in order to elucidate
changes in the surface ocean environment across the EOT. Furthermore, in shelf
deposits, sea-level fluctuations can be traced by evaluating the composition of dinocyst
assemblages, in particular by evaluating the abundance of open marine-, restricted
marine and high energy shelf taxa. We have investigated sections from Northern
Italy, the US Gulf Coast and South Australia and identify sequence boundaries
reflecting sea variability throughout the EOT. Our data indicate that temperature and
ice-volume are not linearly related across the EOT with the first oxygen isotope
step primarily reflecting cooling and the second primarily reflecting ice volume. |
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