Die Prä-PETM Perspektive kurzzeitiger paläoozeanographischer Ereignisse
Zusammenfassung der Projektergebnisse
The overall objective of this project was to assess the marine ecosystem response and the paleoceanographic changes that are related to two Paleocene transient climate events (Latest Danian Event = LDE, 62.2 Ma; Early Late Paleocene Event = ELPE, 58.9 Ma) on a supraregional scale. In order to achieve this we primarily studied planktic foraminiferal assemblages and the geochemistry of foraminiferal tests. We tested to what extent the faunal assemblage composition has been affected by these environmental perturbations in the open ocean system and assessed the pace of these changes. The combination of (I)ODP sites from different ocean basins (North and South Atlantic, Pacific) and latitudes, with Tethyan shelf sections provides a relatively global picture of the plankton assemblage changes. This research project was carried out in close cooperation with the Biogeology Working-Group at the KU Leuven (Belgium) which was focusing on the benthic foraminifera ecosystem. The studied deep-sea sediments document that the LDE is accompanied by negative δ13C (CIE) and δ18O excursions in benthic and planktic foraminiferal calcite. The latter suggests a uniform ocean warming of ~2°C contemporarily to the LDE. The CIE has an amplitude of ~0.8‰ and is a common feature of the LDE. It has now been documented for the Pacific (Sites 1209, 1210), North (Site U1407) and South Atlantic (Site 1262) as well as from the Tethyan shelves of Egypt and Spain. In addition, to the known similarities in sedimentological, environmental and biotic responses between the LDE and the PETM, the documented δ18O decrease with a negative CIE strongly supports the idea that the LDE represents a Paleocene hyperthermal. Planktic foraminiferal assemblages of Site 1262 are dominated by mesotrophic, subsurface taxa such as Subbotina/Parasubbotina, whereas warm, oligotrophic surface waters indicating Morozovella is dominant in the Pacific. At both Sites 1262 and 1210 planktic assemblages consist of a different composition before, during and after the LDE with Morozovella and Igorina becoming more common within the LDE and generally more abundant afterwards. Both sites show the disappearance of Praemurica at the base of the LDE. Our observations imply a short-term specific response to the LDE itself, but also a transition in the total faunal composition on the long run. Our results further show that faunal changes such as the demise of Praemurica and ocean warming started ~170 kyr before the LDE. The Praemurica extinction pattern has been observed at all three deep-sea sites studied in this project suggesting that the environmental changes associated with the LDE passed a certain threshold resulting in a persistent biotic change of the surface ocean biota. This contrasts the response for the benthic deep-sea fauna which is not consistently responding to the LDE, but shows a long-term shift of the sea-floor biota. Concerning the ELPE we conclude that this event does not represent a classical Paleogene hyperthermal event, because it lacks both a negative δ13C and a δ18O excursion. Our records show an increase in carbonate dissolution at the sea floor of different degrees in the three ocean basins. At Shatsky Rise on average 90% of the planktic foraminifera taxa can be considered to represent a warm, oligotrophic surface water environment (Acarinina, Igorina and Morozovella). At the mid latitude sites, the ELPE separates an Igorina-dominated assemblage below from an Acarinina-dominated assemblage above. At Site U1407 subsurface living subbotinids are a much more important component of the assemblage than at the other two sites. Long-term environmental changes are indicated by an overall increase in muricate taxa, specifically acarinids, indicating that the ELPE represents a transitional phase in the assemblage composition on a global scale.
Projektbezogene Publikationen (Auswahl)
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2015. The impact of the Latest Danian Event on planktic foraminifera faunas at ODP Site 1210 (Shatsky Rise, Pacific Ocean). PloS ONE, 10(11), e0141644
Jehle, S., Bornemann, A., Deprez, A., Speijer, R.P.
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2016. Taphonomic impact of ultrasonic treatment on foraminifera from a deep-sea carbonate ooze. J. Micropalaeontol. 35, 229-231
van Bael, R., Deprez, A., Stassen, P., Bornemann, A., Speijer, R.P.
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2017. Differential response at the seafloor during Palaeocene and Eocene ocean warming events at Walvis Ridge, Atlantic Ocean (ODP Site 1262). Terra Nova 29, 71–76
Deprez, A., Jehle, S., Bornemann, A., Speijer, R.P.
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2017. Latest Cretaceous/ Paleocene deep-sea ostracode fauna at IODP Site U1407 (western North Atlantic) with special reference to the Cretaceous/Paleogene boundary and the Latest Danian Event. Mar. Micropaleontol.
Yamaguchi, T., Bornemann, A., Matsui, H., Nishi, H.
