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Demise of the Planktic Foraminifer Genus Morozovella during the Early Eocene Climatic Optimum: New Records from ODP Site 1258 (Demerara Rise, Western Equatorial Atlantic) and Site 1263 (Walvis Ridge, South Atlantic)

1
Department of Physics and Earth Sciences, Ferrara University, via G. Saragat 1, 44121 Ferrara, Italy
2
Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX 77005, USA
3
Department of Earth Sciences, University College London, Gower Street, London WC1E 6BS, UK
4
Department of Earth Sciences, University of California, Riverside, Riverside, CA 92521, USA
*
Author to whom correspondence should be addressed.
Geosciences 2020, 10(3), 88; https://doi.org/10.3390/geosciences10030088
Received: 15 January 2020 / Revised: 10 February 2020 / Accepted: 17 February 2020 / Published: 27 February 2020
Here we present relative abundances of planktic foraminifera that span the Early Eocene Climatic Optimum (EECO) at Ocean Drilling Program (ODP) Site 1258 in the western equatorial Atlantic. The EECO (~53.3−49.1 Ma) represents peak Cenozoic warmth, probably related to high atmospheric CO2, and when planktic foraminifera, a dominant component of marine sediment, exhibit a major biotic response. Consistent with previous work, the relative abundance of the genus Morozovella, which dominated early Paleogene tropical-subtropical assemblages, markedly and permanently declined from a mean percentage of ~32% to less than ~7% at the beginning of the EECO. The distinct decrease in Morozovella abundance occurred at Site 1258 within ~20 kyr before a negative excursion in δ13C records known as the J event and which defines the beginning of EECO. Moreover, all morozovellid species except M. aragonensis dropped in abundance permanently at Site 1258, and this is related to a reduction in test-size. Comparing our data with that from other locations, the remarkable switch in planktonic foraminifera assemblages appears to have begun first with unfavourable environmental conditions near the Equator and then extended to higher latitudes. Several potential stressors may explain observations, including some combination of algal photosymbiont inhibition (bleaching), a sustained increase in temperature, or an extended decrease in pH. View Full-Text
Keywords: Early Eocene Climatic Optimum; planktic foraminiferal changes; bulk carbon isotopes; Morozovella decline; Atlantic Ocean; paleobiogeography; Morozovella test-size reduction Early Eocene Climatic Optimum; planktic foraminiferal changes; bulk carbon isotopes; Morozovella decline; Atlantic Ocean; paleobiogeography; Morozovella test-size reduction
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D’Onofrio, R.; Luciani, V.; Dickens, G.R.; Wade, B.S.; Kirtland Turner, S. Demise of the Planktic Foraminifer Genus Morozovella during the Early Eocene Climatic Optimum: New Records from ODP Site 1258 (Demerara Rise, Western Equatorial Atlantic) and Site 1263 (Walvis Ridge, South Atlantic). Geosciences 2020, 10, 88.

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