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| Titel |
Early to middle Miocene climate evolution: New insights from IODP Sites U1335, U1337 and U1338 (eastern equatorial Pacific Ocean) |
| VerfasserIn |
Karlos G. D. Kochhann, Ann Holbourn, Wolfgang Kuhnt, Mitch Lyle, Isabella Raffi, James E. Channell, Nils Andersen |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104267
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| Publikation (Nr.) |
 EGU/EGU2015-3685.pdf |
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| Zusammenfassung |
| The lower to middle Miocene (~20 to 13 Ma) carbonate-rich sedimentary successions
recovered at Integrated Ocean Drilling Program (IODP) Sites U1335, U1337 and U1338
allow unsurpassed resolution over the Climatic Optimum (16.9-14.7 Ma) and the transition
into a colder climate mode after 13.9 Ma with re-establishment of permanent Antarctic ice
sheets. High-resolution (1-10 kyr) stable carbon (δ13C) and oxygen (δ18O) isotopes of
well-preserved epibenthic foraminifera (Cibicidoides mundulus and Planulina wuellerstorfi)
from these three sites show that the Climatic Optimum was characterized by high-amplitude
climate variations and intense perturbations of the carbon cycle. Episodes of peak warmth
coincided with transient shoaling of the carbonate compensation depth and enhanced
carbonate dissolution in the deep ocean. The U1335 and U1337 records additionally
reveal that the rapid global warming and/or polar ice melting event, marking the
onset of the Climatic Optimum at ~16.9 Ma, was coupled to a massive increase
in carbonate dissolution, indicated by sharp drops in carbonate percentages and
accumulation rates and by the fragmentation or complete dissolution of planktonic
foraminifers. After ~14.7 Ma, stepwise global cooling, culminating with extensive ice
growth over Antarctica at ~13.8 Ma, coincide with enhanced opal and benthic
foraminiferal accumulation rates, suggesting that increased siliceous productivity and
organic carbon burial may have contributed to CO2 drawdown. Integration of age
models derived from orbitally-tuned, high-resolution isotopes, biostratigraphic
data and magnetic reversals allows further constraints on the temporal sequence of
events and helps unravel the drivers of early to middle Miocene climate variations. |
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