Journal cover Journal topic
Journal of Micropalaeontology An open-access journal of The Micropalaeontological Society
J. Micropalaeontol., 35, 79-89, 2016
https://doi.org/10.1144/jmpaleo2014-030
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 4.0 License.
 
01 Jan 2016
The planktic foraminifer Planorotalites in the Tethyan middle Eocene
Flavia Boscolo Galazzo1, Ellen Thomas2,3, Valeria Luciani4, Luca Giusberti1, Fabrizio Frontalini5, and Rodolfo Coccioni5 1Department of Geosciences, University of Padova, Via G. Gradenigo 6, 35131, Padova, Italy
2Department of Geology and Geophysics, Yale University, New Haven, CT, USA
3Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT, USA
4Department of Physics and Earth Sciences, University of Ferrara, Ferrara, Italy
5Department of Earth, Life and Environmental Sciences, University of Urbino ‘Carlo Bo’, Urbino, Italy
Keywords: Planorotalites, Eocene, stable isotopes, Tethys, MECO Abstract. Morphologically uniform, low-trochospiral foraminifera are a common, though not very well-preserved component of foraminiferal assemblages across the interval including the Middle Eocene Climatic Optimum (MECO) at the Alano (northeastern Italy) and Monte Cagnero (central Italy) Tethyan sections. The morphology of these specimens, combined with their state of preservation, made it difficult to assign them to a benthic or planktic group. We measured their stable isotope (oxygen and carbon) composition and compared them with those of trochospiral, epifaunal benthic (Nuttallides truempyi (Nuttall, 1930)) and planktic foraminifera (Acarinina and Subbotina) in the same samples. Despite the preservation, the isotopic analysis showed that the low-trochospiral forms were undoubtedly planktic foraminifera calcifying in the mixed layer. We assign them to the species Planorotalites capdevilensis (Cushman & Bermudez, 1949). Their abundance, distribution and stable isotope values suggest that P. capdevilensis may have been mixed-layer dwellers without photosymbionts, adapted to slightly more mesotrophic conditions than symbiont-bearing, larger acarininids and morozovelloidids. The oxygen isotope data for benthic and planktic species in the two sections are similar, but the carbon isotopic values of all foraminifera are 1.0–1.5 lower at the Alano section than at Monte Cagnero, probably because the Alano sediments were deposited in the more restricted Belluno Basin, the Monte Cagnero sediments in the more open oceanic setting of the Umbria-Marche Basin.

Citation: Galazzo, F. B., Thomas, E., Luciani, V., Giusberti, L., Frontalini, F., and Coccioni, R.: The planktic foraminifer Planorotalites in the Tethyan middle Eocene, J. Micropalaeontol., 35, 79-89, https://doi.org/10.1144/jmpaleo2014-030, 2016.
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