Early Eocene hyperthermal events ETM2, H2 and I1 as recorded by Tethyan planktic foraminifera in the Terche section (northeastern Italy)

• Main Authors: D’Onofrio R., Luciani V., Sprovieri M., GIUSBERTI, LUCA, FORNACIARI, ELIANA
• Other Authors: D’Onofrio, R., Luciani, V., Giusberti, Luca, Fornaciari, Eliana, Sprovieri, M.
• Format: Conference Object
• Language: English
• Published: 2014
• Subjects: Eocene Thermal Maximum 2; Eocene hyperthermal; Planktonic foraminifera; Tethys
• Online Access: http://hdl.handle.net/11577/3016335; http://meetingorganizer.copernicus.org/EGU2014/EGU2014-6425.pdf

In the last years, several transient episodes of extreme warming, the so-called hyperthermals, have been recognized in addition to the well-know Paleocene-Eocene Thermal Maximum (PETM; 55.5 Ma), superimposed on the long-term Paleocene-early Eocene warming trend peaking in the Early Eocene Climatic Optimum (EECO). To the present, perturbations produced by hyperthermals are well documented in terms of isotopic variations whereas their influence on the biota is still largely unexplored. The Terche section, located in the Venetian Pre-Alps (northeastern Italy), is an expanded latest Paleocene-lower Eocene succession deposited in a bathyal setting of a continental margin of the central-western Tethys. This section is particularly suitable to study post-PETM hyperthermals because it contains three well-exposed and expanded marly-clayey units (MUs) corresponding to intervals of negative carbon isotope excursions (CIEs). Calcareous plankton biostratigraphy allow us to refer them to the hyperthermals ETM2 (or H1; 53.7 Ma), H2 (53.6 Ma) and I1(53.3 Ma). Here we present the first detailed quantitative analysis of planktic foraminiferal assemblages across these early Eocene hyperthermals events. Quantitative analysis of planktic foraminiferal genera shows a long-term trend of variation upon which higher frequency variations are superimposed. We interpret such long-term variation as the response to the long–term warming trend since it highlights a slight increase of the warm indicators, such as the acarininids, and decrease of the cold form subbotinids. The high frequency variations, instead, closely related to the CIEs and to the MUs, record a pronounced increase in acarininids (up to 68%) and a parallel marked decline in the abundances of subbotinids and other component of planktic foraminiferal assemblages. The MUs are also associated with an increase of the eutrophic radiolarians. This aspect, together with the dominance of acarininids, can be interpreted as a consequence of the extreme warmth coupled with eutrophic ...