Calcareous plankton response to early Paleogene climate change
Zusammenfassung der Projektergebnisse
The early Paleogene is characterized by a greenhouse climate punctuated by at least two transient hyperthermal events (duration <200 ky) and the longer lasting Early Eocene Climatic Optimum (52-54 Ma). The two hyperthermals cover the Paleocene–Eocene Thermal Maximum (PETM/ETM-1; ~55.5 Ma) and the Elmo (ETM-2) event, which took place about 1.8 Myrs after the PETM. Previously published detailed foraminiferal δ18O and δ13C records for the Paleocene to middle Eocene interval are available from the Southern and Pacific oceans. Here we present new detailed planktic and benthic foraminiferal isotope records from DSDP Site 401 (N Atlantic, Bay of Biscay), which represents one of the most northern scientific drill sites providing pelagic carbonates of Paleocene to middle Eocene age. This interval has been investigated with respect to the δ18O and δ13C composition of planktic and benthic foraminifera, which are compared to assemblage changes of calcareous nannofossils and planktic foraminifera in order to study their response to paleoceanographic changes. The availability of well preserved foraminiferal tests makes this site suitable for correlation and comparison with other long term records from the Pacific (Guyot Plateau, Shatsky Rise) and the Southern Ocean (Maud Rise). Site 401 also provides the third deep-sea planktic foraminiferal isotope record for the PETM besides Maud Rise and Shatsky Rise. Benthic foraminiferal data of both δ13C and δ18O are well in line with the multi-site compilation of Zachos et al. (2008, Nature). By contrast, surface dwelling planktic foraminifera don’t show any indication for a middle Eocene cooling, while subsurface dwelling taxa show only a minor increase in δ18O. This again raises doubt about a general surface water cooling as proposed by Pearson et al. (2007, Geology) based on data from Tanzania. During the well developed PETM the δ18O of surface-dwelling and benthic foraminifera are decoupled during the recovery phase of the carbon isotope excursion. This suggests either different temperature histories or salinities for the different water-masses or changes in the deep-water source. A pronounced pulse of kaolinite deposition, begun shortly after the start of the PETM and persists at least for several hundred thousand years after the termination of the CIE. The prolonged period of clay deposition suggests that the PETM fundamentally altered either weathering conditions or run-off long after the end of the climatic transient. Assemblage changes provide major changes, extinctions and originations of new calcareous plankton taxa during the latest Paleocene and early Eocene. On the contrary assemblage composition is more stable during the middle Eocene. This is consistent with the observed low surface water variability as reflected by stable surface water δ13C and δ18O signatures.
Projektbezogene Publikationen (Auswahl)
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(2008): A preliminary calcareous plankton biostratigraphy of the Paleocene- Eocene interval at DSDP Site 401 (Bay of Biscay). – German IODP-ICDP Colloquium (Hannover)
Bornemann, A.
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(2008): Calcareous nannofossil and planktic foraminiferal biostratigraphy of the Paleocene-Eocene interval in the Bay of Biscay. – EGU General Assembly (Vienna)
Bornemann, A.
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(2009). Detection of early Eocene hyperthermals using benthic foraminifera (fauna and stable isotopes) at DSDP Site 401, Bay of Biscay, North Atlantic. Challenges for the Planet: Earth Sciences' perspective. International Conference Geologica Belgica (Gent)
D'haenens, S., Bornemann, A. & Speijer, R.
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(2009): Foraminiferal stable isotope records from the North Atlantic Ocean for the late Paleocene to middle Eocene interval (DSDP Site 401). – AGU Fall Meeting (San Francisco)
Bornemann, A., D’haenens, S. & Speijer, R.P.
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(2009): The latest Paleocene to middle Eocene interval in the Bay of Biscay – preliminary results from calcareous nannofossils and planktic foraminifera. – EGU General Assembly (Vienna)
Bornemann, A.
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(2009): The Paleocene-Eocene transition in the Bay of Biscay (DSDP Site 401). – German IODP-ICDP Colloquium (Potsdam)
Bornemann, A.
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(2010): Benthic foraminiferal response during early Eocene hyperthermals at DSDP Site 401, Bay of Biscay, North East Atlantic. – Forams 2010 (Bonn)
D’haenens, S., Bornemann, A., Röhl, U., Stassen, P. & Speijer, R.P.
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(2010): Detection and characterization of early Eocene hyperthermals using benthic foraminiferal associations and stable isotopes at DSDP Site 401, Bay of Biscay, North East Atlantic. – EGU General Assembly (Vienna)
D’haenens, S., Bornemann, A., Röhl, U. & Speijer, R.P.
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(2010): Detection and characterization of early Eocene hyperthermals using benthic foraminiferal associations and stable isotopes at DSDP Site 401, Bay of Biscay, North East Atlantic. – The Micropalaeontological Society Annual Meeting (London)
D’haenens, S., Bornemann, A., Röhl, U. & Speijer, R.P.
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(2010): Detection and characterization of early Eocene hyperthermals using benthic foraminiferal associations and stable isotopes. – 3rd International Palaeontological Congress (London)
D‘haenens, S., Bornemann, A., Röhl, U. & Speijer, R.P.
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(2010): New insights into transient and long-term paleoceanographic changes during the late Paleocene to middle Eocene in the NE Atlantic. – 10th International Conference on Paleoceanography (San Diego)
Bornemann, A., D’haenens, S., Lyman, J.A., Norris, R.D., Röhl, U. & Speijer, R.P.
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(2010): New stable isotope records from the Atlantic Ocean for the Paleocene to Eocene interval (DSDP Site 401): What do they tell us? – EGU General Assembly (Vienna)
Bornemann, A., D’haenens, S. & Speijer, R.P.
