 |
| Titel |
Mid-Pliocene North Atlantic palaeoceanography based on palynology, planktonic foraminiferal Mg/Ca, and alkenones |
| VerfasserIn |
Stijn De Schepper, Jeroen Groeneveld, Martin J. Head, David Naafs |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035670
|
|
|
|
|
|
| Zusammenfassung |
| The mid-Pliocene was an episode of prolonged global warmth and strong North Atlantic
thermohaline circulation, interrupted briefly at ca. 3.30 Ma by a global cooling event
corresponding to Marine Isotope Stage (MIS) M2. We have combined Mg/Ca ratios and δ18O
from Globigerina bulloides with dinoflagellate cyst assemblage data from three IODP/DSDP
sites to reconstruct the palaeoceanography of the eastern North Atlantic between ca. 3.4 and
3.2 Ma.
Sea-surface temperature reconstructions indicate warm waters at IODP Site 1308 and DSDP
Site 610 before and after MIS M2, but a cooling of ca. 2–3Ë C during MIS M2. A
dinoflagellate cyst assemblage overturn, characterized by a significant decline in
Operculodinium centrocarpum at those sites, points to a reduced northward heat transport and
weakened influence of the NAC. The reduced northward heat transport at the northerly sites
occurs about 23–35 ka in advance of the maximum global ice volume of MIS M2. Hence, it
has been suggested that changes in North Atlantic circulation led to the expansion of the
Greenland ice-sheet and initiated the global cooling event at MIS M2. Preliminary results
from the more southerly IODP Site U1313 do not record the marked changes of the northerly
site. Our foraminiferal Mg/Ca data and the dinoflagellate cyst assemblages shows only
minor variability and no expressed cooling around MIS M2, suggesting that only the
higher latitudes experienced significant cooling. In contrast, cooling is reflected
around that time in an alkenone based sea surface temperature record from the same
site.
Our multiproxy approach allows a first attempt at unravelling the ecological preferences of
extant and extinct Pliocene dinoflagellate cysts. For at least one species, Impagidinium
pallidum, a contradiction is apparent between its present and Pliocene spatial and temporal
distributions, which could be explained by changes in seasonality, transport paths, or
ecological preference. |
|
|
|
|
|
|