Diachrony between shallow-water and pelagic crisis: the example of the Bartonian-Priabonian boundary

• Main Author: PAPAZZONI, Cesare Andrea
• Other Authors: Bucur I.I., Lazar I. & Sasaran E., Papazzoni, Cesare Andrea
• Format: Conference Object
• Language: English
• Published: Cluj University Press 2015
• Subjects: Middle-Upper Eocene; Biostratigraphy; Larger Foraminifera; Calcareous plankton; Correlation; Planktonic foraminifera
• Online Access: http://hdl.handle.net/11380/1075223

One of the major goals of the International Commission on Stratigraphy is to define the GSSP (Global Stratotype Section and Point) for each of the basic subdivisions (stages) of the chronostratigraphic scale. In the Paleogene, most of the stages have defined GSSPs, but still Bartonian, Priabonian, and Chattian have not. The base of the Priabonian is especially interesting since it occurred lose to the last greenhouse-icehouse transition (e.g., Zachos et al., 2001). The Eocene-Oligocene boundary was for sure a bigger crisis, nevertheless the Middle-Upper Eocene boundary (=Bartonian-Priabonian) recorded a profound change in the shallow water communities, the extinction of all the large species of nummulites being one of the more conspicuous. In the pelagic realm, the extinction of the muricate planktonic foraminifera and some changes in the calcareous nannoplankton assemblages also mark a generalized biotic turnover. Mass extinctions are defined as differing from the so-called ‘background’ extinctions because of their speed and intensity (Armstrong & Brasier, 2005), but several authors pointed out that they are also poorly or definitely non-selective (Jablonski, 2005) and affecting different paleoenvironments. Therefore, the Bartonian-Priabonian transition, aside for the relatively low intensity, seems to fit the requirements to be ascribed to a (minor) mass extinction event. A good chance to check wether the extinction events were contemporary or not in the shallow and deep water environments came by the work to find a section suitable for establishing the GSSP for the base of the Priabonian. A good pelagic section close to the type area of the Priabonian in northern Italy was intensively studied in Alano di Piave (northern Italy; Agnini et al., 2011). Here, several extinction and appearances among planktonic foraminifera and calcareous nannoplankton were carefully recorded, and the extinction of the muricate large acarininids and Morozovelloides were proposed as one of the possible markers of the base of the ...