Identification of the base of the lower-to-middle Campanian Globotruncana ventricosa Zone: Comments on reliability and global correlations Maria Rose Petrizzo * , Francesca Falzoni, Isabella Premoli Silva Dipartimento di Scienze della Terra “A. Desio”, Università degli Studi di Milano, via Mangiagalli 34, I-20133 Milano, Italy article info Article history: Received 11 April 2010 Accepted in revised form 28 January 2011 Available online 4 February 2011 Keywords: Planktic foraminifera Taxonomy Biozonation Campanian Tethys Southern Ocean abstract The reliability of the first appearance datum of Globotruncana ventricosa as biozonal marker for the Campanian is discussed. The taxonomy and species concept of G. ventricosa and of Globotruncana tricar- inata, that has been either regarded as junior synonym of Globotruncana linneiana or of G. ventricosa, are examined to avoid misidentifications, and one species is here formally described as new, Globotruncana neotricarinata nov. sp. The tropical and subtropical planktic foraminiferal assemblages from the Bottac- cione section (Gubbio, Italy), from Deep Sea Drillig Project (DSDP) Site 146 (Caribbean Sea, central Atlantic Ocean), and from Ocean Drilling Program (ODP) Hole 1210B (Shatsky Rise, northwestern Pacific Ocean) are analyzed for the presence of biostratigraphic markers. Lowest and highest occurrence data have been checked in thin sections and washed residues in the Bottaccione section. The comparative biostratigraphic analysis of the planktic foraminiferal distribution highlights: 1) the absence of G. ventricosa at the strati- graphic level at which it is supposed to first occur in the Tethyan area, 2) the presence of transitional specimens resembling G. ventricosa and thus erroneously used to identify the base of the G. ventricosa Zone, 3) the presence of a good sequence of bioevents that appear to be promising for regional and global correlations such as the appearance of Globotruncanita atlantica, Contusotruncana plummerae and the disappearance of Hendersonites carinatus. The correlation potential of these bioevents has been verified across latitudes by studying the Campanian planktic foraminiferal assemblage in pelagic sediments drilled on coastal Tanzania (western Indian Ocean), and at the deep-sea ODP Hole 762C (Exmouth Plateau, western Indian Ocean), that were located at 30  S and 47  S in the Late Cretaceous, respectively. Besides the known diachronous first appearance of G. ventricosa in the Southern Ocean sites, results confirm the difficulty in using G. ventricosa as zonal marker in the tropical and subtropical areas, and the validity of the first appearance datum of C. plummerae for regional and global correlations. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Lower-to-middle Campanian tropical and subtropical bio- zonation based on planktic foraminifera prevents a high strati- graphic resolution when compared with other Cretaceous intervals. In the Tethyan planktic foraminiferal biozonation the stratigraphic interval between the extinction level of Dicarinella asymetrica and the appearance of Radotruncana calcarata is subdivided in two biozones (Globotruncanita elevata and Globotruncana ventricosa Zones) based on the first occurrence of G. ventricosa (Premoli Silva and Sliter, 1995; Robaszynski and Caron, 1995). Specifically, the G. elevata and G. ventricosa Zones correspond to a time interval of 3.5 my and of 4.0 my, respectively (Gradstein et al., 2004). Some difficulties in using the first occurrence datum of G. ven- tricosa have been observed in the low latitude sections from the Tethyan Realm (Tunisia: Robaszynski et al., 2000), in the Central Atlantic Ocean (Bahamas Islands: Caron, 1972; Caribbean Sea: Premoli Silva and Bolli, 1973), and in the Pacific area (Shatsky Rise: Bralower et al., 2002; Caron, 1975). Moreover, it is well known that the appearance of G. ventricosa in the southern mid-high latitudes is recorded in sediments yielding marginotruncanids, extending its vertical range down to the Santonian (Rexilius, 1984; Wonders, 1992; Petrizzo, 2000, 2001, 2003) and probably Coniacian (Herb, 1974). Thus, this bioevent is diachronous across latitudes. The primary aim of this paper is to investigate the reliability of the first appearance datum of G. ventricosa by comparing lower-to- middle Campanian sections from different localities across lati- tudes (Fig. 1). The taxonomy and the stratigraphic range of G. ventricosa and of some index species that are often overlooked or * Corresponding author. Tel.: þ39 02 50315531; fax: þ39 02 50315494. E-mail address: mrose.petrizzo@unimi.it (M.R. Petrizzo). Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes 0195-6671/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2011.01.010 Cretaceous Research 32 (2011) 387e405