Clim. Past Discuss., 7, 2089-2118, 2011
www.clim-past-discuss.net/7/2089/2011/
doi:10.5194/cpd-7-2089-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Productivity response of calcareous nannoplankton in the South Atlantic to the Eocene Thermal Maximum 2 (ETM2)
M. Dedert1, H. M. Stoll2,3, D. Kroon4, N. Shimizu5, and P. Ziveri1,6
1Section of Marine Biogeology, Department of Earth Sciences, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
2Dept. de Geologia, Universidad de Oviedo, Asturias, Spain
3Geoscience Department, University of Massachusetts at Amherst, Amherst, MA, USA
4School of Geosciences, University of Edinburgh, Edinburgh, UK
5Geology and Geophysics Department, Woods Hole Oceanographic Institute, Woods Hole, MA, USA
6ICTA, Autonomous University of Barcelona (UAB), Bellaterra, Spain

Abstract. The Early Eocene Thermal Maximum 2 (ETM2) at ~53.7 Ma is one of multiple hyperthermal events that followed the Paleocene-Eocene Thermal Maximum (PETM, ~55 Ma). In order to reconstruct the primary productivity response to the ETM2 in the South Atlantic, we have analyzed Sr/Ca ratios in various size fractions of bulk sediments and in picked monogeneric populations of calcareous nannofossils. The latter technique of measuring selected nannofossil populations using the ion probe circumvents possible contamination with secondary calcite. Avoiding such contamination is important for interpretation of the nannoplankton productivity record, since diagenetic processes can bias the productivity signal, as we demonstrate for Sr/Ca measurements in the fine (<20 um) and other size fractions obtained from bulk sediments. The paleoproductivity signal as reconstructed from the Sr/Ca ratios appears to be dominantly governed by cyclic orbital forcing. The ~13 to 21 % increase in Sr/Ca above the cyclic background conditions as measured by ion probe in dominating genera is likely the result of a slightly elevated productivity during ETM2. This high productivity phase is the result of enhanced nutrient supply either from land or from upwelling. Our results show that calcareous nannoplankton productivity was not reduced by environmental conditions accompanying ETM2, but even showed a small increase during the extreme climatic conditions of ETM2.

Citation: Dedert, M., Stoll, H. M., Kroon, D., Shimizu, N., and Ziveri, P.: Productivity response of calcareous nannoplankton in the South Atlantic to the Eocene Thermal Maximum 2 (ETM2), Clim. Past Discuss., 7, 2089-2118, doi:10.5194/cpd-7-2089-2011, 2011.
 
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