The Bartonian-Priabonian transition in the Mossano section (Colli Berici, north-eastern Italy): a tentative correlation between calcareous plankton and shallow-water benthic zonations

The revision of the benthic and planktic biostratigraphic events across the Bartonian-Priabonian boundary is in progress in the frame of the I. G. C. P. project no. 393 (Neritic events at the Middle-Upper Eocene boundary). Here we present the biostratigraphic correlation between calcareous plankton (planktic foraminifers and calcareous nannofossils) and larger foraminifers at the Bartonian/Priabonian boundary in the Mossano section (Colli Berici, Vicenza), which has been proposed as a possible parastratotype for the Priabonian (Colloque sur l'Eocene, Paris, 1968). The Bartonian-Priabonian boundary has been so far defined on the basis of the first occurrence of Nummulites fabianii. In the Mossano section, this event occurs at the Calcari Nummulitici-Marne di Priabona boundary. We have investigated a stratigraphic section spanning the first 11 m of the Marne di Priabona. According to the planktic foraminiferal assemblages, the interval studied is referable to the upper part of the P15 Zone and to the basal part of the P16 Zone. The calcareous nannofossil study allows to refer the interval studied to the NP17/18 and NP19/20 Zones. The calcareous plankton zones correlate to the larger foraminifers SBZ19 (Late Eocene). The calcareous nannofossil Isthmolithus recurvus (identifying the NP19/20 Zone) was observed a few metres above the base together with the most evolved form of the planktic foraminiferal cerroazulensis lineage. These findings and the absence of Globigerinatheka semiinvoluta (P16 Zone) in the upper part of the segment analysed at Mossano suggest that it is referable to the uppermost Priabonian. Unfortunately, the absence of calcareous plankton in the Calcari ummulitici underlying the Marne di Priabona prevents the direct identification of possible bioevents coinciding with the FO of N. fabianii. As a consequence, condensation or hiatus cannot be excluded. The correlation with planktic microfossil and larger foraminiferal events appears to be in agreement with the data from shallow-water successions of northern Egypt. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.