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| Titel |
Expansion and diversification of high-latitude radiolarian assemblages in the late Eocene linked to a cooling event in the southwest Pacific |
| VerfasserIn |
K. M. Pascher, C. J. Hollis, S. M. Bohaty, G. Cortese, R. M. McKay, H. Seebeck, N. Suzuki, K. Chiba |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 12 ; Nr. 11, no. 12 (2015-12-07), S.1599-1620 |
| Datensatznummer |
250117485
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| Publikation (Nr.) |
 copernicus.org/cp-11-1599-2015.pdf |
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| Zusammenfassung |
| The long-term cooling trend from middle to late Eocene was punctuated by
several large-scale climate perturbations that culminated in a shift to
"icehouse" climates at the Eocene–Oligocene transition. We present
radiolarian micro-fossil assemblage and foraminiferal oxygen and carbon
stable isotope data from Deep Sea Drilling Project (DSDP) sites 277, 280,
281, and 283 and Ocean Drilling Project (ODP) Site 1172 to identify significant
oceanographic changes in the southwest Pacific through this climate
transition (~ 40–30 Ma). We find that the Middle Eocene
Climatic Optimum at ~ 40 Ma, which is truncated but identified
by a negative shift in foraminiferal δ18O values at Site 277,
is associated with a small increase in radiolarian taxa with low-latitude
affinities (5 % of total fauna). In the early late Eocene at
~ 37 Ma, a positive oxygen isotope shift at Site 277 is
correlated with the Priabonian Oxygen Isotope Maximum (PrOM). Radiolarian
abundance, diversity, and preservation increase within this cooling event at
Site 277 at the same time as diatom abundance. A negative δ18O
excursion above the PrOM is correlated with a late Eocene warming event
(~ 36.4 Ma). Radiolarian abundance and diversity decline
within this event and taxa with low-latitude affinities reappear. Apart from
this short-lived warming event, the PrOM and latest Eocene radiolarian
assemblages are characterised by abundant high-latitude taxa. High-latitude
taxa are also abundant during the late Eocene and early Oligocene
(~ 38–30 Ma) at DSDP sites 280, 281, 283 and 1172 and are
associated with very high diatom abundance. We therefore infer a northward
expansion of high-latitude radiolarian taxa onto the Campbell Plateau in the
latest Eocene. In the early Oligocene there is an overall decrease in
radiolarian abundance and diversity at Site 277, and diatoms are scarce.
These data indicate that, once the Antarctic Circumpolar Current was
established in the early Oligocene (~ 30 Ma), a frontal system
similar to present day developed, with nutrient-depleted Subantarctic
waters bathing the area around DSDP Site 277, resulting in a more restricted
siliceous plankton assemblage. |
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