In search of the Burdigalian GSSP: new evidence from the Contessa Section (Italy)

Alessio Fabbrini (1), Niccolò Baldassini (2), Chiara Caricchi (3), Luca Maria Foresi (1) (4), Leonardo Sagnotti (3), Jaume Dinarès-Turell (3), Agata Di Stefano (2), Fabrizio Lirer (5), Marco Menichetti (6), Aldo Winkler (3) & Salvatore Distefano (2)
(1) Dipartimento di Scienze Fisiche della Terra e dell’Ambiente, Università degli studi di Siena, Via Laterina 8, 53100 Siena, Italia. (2) Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania, Corso Italia 55, 95129 Catania. (3) Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, 00143 Roma, Italia. (4) Istituto di Geoscienze e Georisorse, CNR, Via G. Moruzzi 1, 56124 - Pisa, Italia. (5) Istituto di Scienze Marine (ISMAR)-CNR - Sede di Napoli, Calata Porta di Massa, Interno Porto di Napoli 80133, Napoli Italy. (6) Dipartimento di Scienze Pure ed Applicate, Università degli studi di Urbino Carlo Bò, Via Ca’ le Suore 2-4, 61029, Urbino, Italia. Corresponding author e-mail: fabbrini21@student.unisi.it, tel. +39 0577 233804.

The Contessa Section is a reference section for the early Miocene in the Mediterranean. Along this 36 m thick section 115 samples were collected and analysed for an integrated bio-magnetostratigraphic study through the Scaglia Cinerea and Bisciaro formations. Planktonic foraminifera were analysed semi-quantitatively, while calcareous nannofossils were examined using the standard quantitative method. A reliable biozonation for both fossil groups was then accomplished. The paleomagnetic analyses identified a sequence of magnetozones, then correlated with the ATNTS using the calcareous plankton bioevents. The investigated interval extends from foraminiferal Zone P22 (Chattian) to MMi2c (Burdigalian) and from calcareous nannofossils Zone MNP25a to MNN3a, thus from Chron C7An to C5En. Therefore, the section chronologically spans from 24.80 Ma to 18.10 Ma. Three hiatuses were recognised along the section: H1 at 0.63 m from the base (comprising a minimum time interval from 24.36 Ma to 23.38 Ma), H2 at 12.33 m (between 21.80 Ma and 21.35 Ma) and H3 at 34.03 (between 19.21 Ma and 18.40 Ma). All three hiatuses were correlated with regional megahiatuses identified in the North Atlantic Ocean and in the Paratethys area. Furthermore, the First Occurrence of the calcareous nannofossil Helicosphera ampliaperta is recognised within Chron C6An.2n at 19.77 m from the base (6 m above the volcaniclastic Raffaello Level). This event provisionally defines the Aquitanian/Burdigalian boundary according to the literature. Thus, the Contessa Section is a possible candidate for the definition of the Burdigalian Global Stratigraphic Section and Point. Finally, the age of the Raffaello Level (a regional marker horizon for the early Miocene) is discussed in this new integrated stratigraphic framework, falling in Chron C6AAn and dated between 21.09 Ma and 21.08 Ma.

Early Miocene, integrated biostratigraphy, planktonic foraminifera, calcareous nannofossils, Mediterranean, magnetostratigraphy, GSSP.