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| Titel |
Paleoceanography of marine isotope stage 31 (ca. 1.07 Ma) in the Labrador Sea based on palynological, microfaunal and isotopic data |
| VerfasserIn |
Aurelie Aubry, Anne de Vernal, Claude Hillaire-Marcel |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093916
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| Publikation (Nr.) |
 EGU/EGU2014-9109.pdf |
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| Zusammenfassung |
| We have documented the paleoceanography of marine isotope stage (MIS) 31 (ca. 1.07 Ma)
at IODP Site 1305 off southwest Greenland in the Labrador Sea, based on dinocyst and
foraminifer populations in addition to isotopic measurements in planktonic foraminiferal
shells. The planktonic foraminifer assemblages are dominated by the mesopelagic species
Neogloboquadrina pachyderma sinistral (Nps). Current interpretations of Nps dominance
would thus point to a polar type environment. However, dinocyst assemblages are dominated
by Operculodinium centrocarpum, Nematosphaeropsis labyrinthus and Bitectatodinium
tepikiense, which rather indicate temperate-subpolar environnement conditions in the photic
zone. Assuming that Nps ecological requirements were unchanged, reconciling the two
observations lead to hypothesize a strong stratification of the surface water layer over a
subsurface water mass, with Nps ocupying the pycnocline in between. We tentatively
applied the modern analogue technique (MAT) to reconstruct surface water conditions
from the dinocyst assemblages. Good analogues are found in the modern dinocyst
database (n=1492), notably along the southeast Canadian margins and northwest
European margins. They indicate a low salinity in the surface waters (32-34.5),
a large seasonal amplitude of temperatures with cool winters (3-6°C) and mild
summer (10-15°C). Stable isotope measurements in Nps point to δ18O ranging
1.5-2.2o throughout most of the interval, thus significantly lower than those measured
during the Holocene (>2.2o at this very site. Benthic isotopic values (~3.2o are
in accordance with the global stack of Lisiecki and Raymo (Paleoceanography,
2005). This suggests the presence of relatively warm water intermediate mass in
between the bottom and surface water masses. The isotopic, micropaleontological and
dinocyst results together show that conditions were unfavorable for convection
and intermediate or deep water formation in the Labrador Sea during this interval. |
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