Cretaceous Research (2000) 21, 479–505 doi:10.1006/cres.2000.0218, available online at http://www.idealibrary.com on Upper Turonian–lower Campanian planktonic foraminifera from southern mid–high latitudes (Exmouth Plateau, NW Australia): biostratigraphy and taxonomic notes Maria Rose Petrizzo Dipartimento di Scienze della Terra, Universita ` degli Studi di Milano, via Mangiagalli, 34, 20133 Milano, Italy; e-mail: mrose@e35.gp.terra.unimi.it Revised manuscript accepted 13 March 2000 A planktonic foraminiferal zonal scheme is presented for subdivision of the Upper Cretaceous pelagic carbonate sequence from southern mid–high latitudes. Definition of the zones is based on first and last occurrences of planktonic foraminifera from Ocean Drilling Program Holes 762C and 763B (Leg 122; Exmouth Plateau, south Indian Ocean). During the Late Cretaceous the studied holes were located close to 50S and for the first time a complete sedimentary record for the mid–high latitudes was obtained. A detailed biostratigraphic analysis has allowed recognition of two new zones (Falsotruncana maslakovae Zone and Marginotruncana marianosi Zone) for the interval extending from the last occurrence of Helvetoglo- botruncana helvetica to the first occurrence of Dicarinella asymetrica (upper Turonian–lower Santonian). From this study it is apparent that some low latitude (Globotruncana ventricosa, Hedbergella flandrini, Marginotruncana marianosi) and high latitude (Globigerinelloides impensus and Hedbergella sliteri) marker taxa display a vertical distribution at mid–high latitudes which is different from that known from low latitudes; moreover, one species (Heterohelix papula), overlooked at low latitudes, exhibits a restricted range that seems to be useful for chrono-biostratigraphic correlations: its appearance is suggested to coincide with the Coniacian/Santonian boundary. The proposed biozonation, which is integrated with calcareous nannofossil and magnetostratigraphic data available for the sections studied, is compared with both the low-latitude standard zonation and the planktonic foraminiferal zonal scheme for the circum-Antarctic region, in order to define a bio-chronostratigraphic scale that is useful for mid–high latitudes of the southern oceans.  2000 Academic Press K W: planktonic foraminifera; biostratigraphy; late mid-Turonian–early Campanian; southern mid–high latitudes; taxonomy. 1. Introduction Most of the biostratigraphic and palaeoenvironmental studies on the Cretaceous of the southern oceans have been hampered by no or poor sedimentary recovery, especially from the middle Turonian–lower Campanian interval. So far, the best Cretaceous record from southern latitudes deals with the upper- most Campanian–upper Maastrichtian interval, for which sedimentary record is almost complete (Huber, 1990, 1991a, b, 1992a, b). On the other hand, in most southern latitude drill-sites the record of the upper Turonian is scarce and discontinuous, and very poor for the Cenomanian–middle Turonian. The poor recovery and the incompleteness of the stratigraphic record along with the absence of several zonal marker taxa at these latitudes has prevented the establish- ment of a planktonic foraminiferal biostratigraphic zonation, even on a regional scale; consequently, any accurate correlation among the existing southern ocean deep-sea sites (Herb, 1974; Sliter, 1977; Krasheninnikov & Basov, 1983; Huber, 1990, 1991a, b, 1992b; Quilty, 1992). A more complete record of mid–high latitude Cretaceous planktonic foraminifera was obtained during Ocean Drilling Program (ODP) Leg 122 (Sites 762 and 763) than any encountered previously. It was also the first to be documented from the eastern Indian Ocean (Wonders, 1992). Relevant information from previous deep-sea drilling in this area (Deep Sea Drilling Project) is rather scanty. Herb (1974) described the fragmentary record of Cretaceous planktonic foraminifera from DSDP Leg 26 and pointed out the low diversity and the predominance of non-keeled species of the genera Archaeoglobigerina, Globigerinelloides, Hedbergella and Whiteinella in the 0195–6671/00/040479+27 $35.00/0  2000 Academic Press