Dinoflagellate cysts and mid-Oligocene chronostratigraphy in the central Mediterranean region

Abstract

Two new dinoflagellate cyst zones are proposed, linking previously established zonal schemes for the Eocene–Oligocene and Oligocene–Miocene successions in the central Mediterranean region. The Hystrichokolpoma pusillum (Hpu) and Chiropteridium lobospinosum (Clo) interval zones are based on the Contessa Quarry and Monte Cagnero sections (central Italy), and are correlated with previously established magnetostratigraphical and biostratigraphical schemes. The base of the Chattian is considered to correlate with Chron Cl0n. In central Italy, the most distinct dinoflagellate cyst event associated with this chron is the first occurrence of Distatodinium biffii, marking the base of the Distatodinium biffii (Dbi) Zone. Indirect evidence also suggests that the first occurrence of Distatodinium biffii is above but close to the base of the Chattian Stage in its type area in northwest Germany, thus making it an important marker. Other possible markers for the base of the Chattian are the last occurrence of Areosphaeridium pectiniforme and the lowest acme of Chiropteridium spp. The latter may be related to the major mid-Oligocene sea-level fall (TA–TB Exxon supercycle boundary), also considered to represent the base of the Chattian and previously correlated with Chron Cl0n. However, in the Contessa Quarry section this dinoflagellate cyst event is associated with the older Chron C11.