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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 4
Clim. Past, 12, 981–1007, 2016
https://doi.org/10.5194/cp-12-981-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Climatic and biotic events of the Paleogene

Clim. Past, 12, 981–1007, 2016
https://doi.org/10.5194/cp-12-981-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 15 Apr 2016

Research article | 15 Apr 2016

Major perturbations in the global carbon cycle and photosymbiont-bearing planktic foraminifera during the early Eocene

Valeria Luciani1, Gerald R. Dickens2,3, Jan Backman2, Eliana Fornaciari4, Luca Giusberti4, Claudia Agnini4, and Roberta D'Onofrio1 Valeria Luciani et al.
  • 1Department of Physics and Earth Sciences, Ferrara University, Polo Scientifico Tecnologico, Via G. Saragat 1, 44100 Ferrara, Italy
  • 2Department of Geological Sciences, Stockholm University, 10691 Stockholm, Sweden
  • 3Department of Earth Science, Rice University, Houston, TX 77005, USA
  • 4Department of Geosciences, Padova University, Via G. Gradenigo 6, 35131 Padova, Italy

Abstract. A marked switch in the abundance of the planktic foraminiferal genera Morozovella and Acarinina occurred at low-latitude sites near the start of the Early Eocene Climatic Optimum (EECO), a multi-million-year interval when Earth surface temperatures reached their Cenozoic maximum. Stable carbon and oxygen isotope data of bulk sediment are presented from across the EECO at two locations: Possagno in northeast Italy and Deep Sea Drilling Project (DSDP) Site 577 in the northwest Pacific. Relative abundances of planktic foraminifera are presented from these two locations, as well as from Ocean Drilling Program (ODP) Site 1051 in the northwest Atlantic. All three sections have good stratigraphic markers, and the δ13C records at each section can be correlated amongst each other and to δ13C records at other locations across the globe. These records show that a series of negative carbon isotope excursions (CIEs) occurred before, during and across the EECO, which is defined here as the interval between the J event and the base of Discoaster sublodoensis. Significant though ephemeral modifications in planktic foraminiferal assemblages coincide with some of the short-term CIEs, which were marked by increases in the relative abundance of Acarinina, similar to what happened across established hyperthermal events in Tethyan settings prior to the EECO. Most crucially, a temporal link exists between the onset of the EECO, carbon cycle changes during this time and the decline in Morozovella. Possible causes are manifold and may include temperature effects on photosymbiont-bearing planktic foraminifera and changes in ocean chemistry.

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The symbiont-bearing planktic foraminiferal genera Morozovella and Acarinina were among the most important calcifiers of the early Paleogene tropical and subtropical oceans. However, a remarkable and permanent switch in the relative abundance of these genera happened in the early Eocene. We show that this switch occurred at low-latitude sites near the start of the Early Eocene Climatic Optimum (EECO), a multi-million-year interval when Earth surface temperatures reached their Cenozoic maximum.
The symbiont-bearing planktic foraminiferal genera Morozovella and Acarinina were among the most...
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