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| Titel |
Late Eocene stable isotope stratigraphy of North Atlantic IODP Site U1411:
Orbitally paced climatic heartbeat at the close of the Eocene greenhouse |
| VerfasserIn |
Helen Coxall, Steve Bohaty, Paul Wilson, Diederik Liebrand, Anna Nyberg, Max Holmström |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133863
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| Publikation (Nr.) |
 EGU/EGU2016-14522.pdf |
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| Zusammenfassung |
| Integrated Ocean Drilling Program (IODP) Expedition 342 drilled sediment drifts on the
Newfoundland margin to recover high-resolution records of North Atlantic ocean-climate
history and track the evolution of the modern climate system through the Late Cretaceous and
Early Cenozoic. An early Paleogene deep-sea benthic stable isotope composite
record from multiple Exp. 342 sites is currently in development and will provide a
key reference section for investigations of Atlantic and global climate dynamics.
This study presents initial results for the late Eocene slice of the composite from
Site U1411, located at mid depth (∼2850m Eocene paleodepth) on the Southeast
Newfoundland Ridge. Stable oxygen (δ18O) and carbon (δ13C) isotope ratios were
measured on 640 samples hosting exceptionally well-preserved epifaunal benthic
foraminifera obtained from the microfossil-rich uppermost Eocene clays at 4cm
spacing. Sedimentation rates average 2-3 cm/kyr through the late Eocene, such
that our sampling resolution is sufficient to capture the dominant Milankovitch
frequencies. Late Eocene Site U1411 benthic δ18O values (1.4 to 0.5‰ VPDB) are
comparable to the Pacific and elsewhere in the Atlantic at similar depths; however,
δ13C is lower by ∼0.5 ‰ with values intermediate between those of the Southern
Labrador Sea to the north (-1 to 0 ) and mid latitude/South Atlantic (0.5 to 1.5 ) to
the south, suggesting poorly ventilated bottom waters in the late Eocene North
Atlantic and limited production of North Atlantic deep water. Applying the initial
shipboard magneto-biostratigraphic age framework, the Site U1411 benthic δ13C and
δ18O records display clear cyclicity on orbital timescales. Spectral analysis of the
raw unfiltered datasets identifies eccentricity (400 and 100 kyr), obliquity (40 kyr)
and precession (∼20 kyr) signals imprinted on our time series, revealing distinct
climatic heart beats in the late Eocene prior to the transition into the ‘ice house’. |
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