All eight sites (1207–1214) drilled on Shatsky Rise during Ocean Drilling Program (ODP) Leg 198 recovered Cretaceous sediments that range in age from Berriasian to Maastrichtian. Maastrichtian–Campanian sediments predominantly composed of pure, white nannofossil ooze were recovered at six of the sites (1207–1212); drilling at three of these (Sites 1209–1211) was terminated due to increasing amounts of chert, and at four sites (1208 and 1212–1214) hiatuses were encountered that incorporate much of the pre-Campanian Upper Cretaceous. Turonian and Coniacian sediments appear to have been recovered at Sites 1207 and 1212, but recovery was extremely poor due to pervasive chert beds and apparent hiatuses. At five sites (1207, 1208, and 1212–1214) chert, porcellanite, and nannofossil ooze-dominated mid-Cretaceous sections (Aptian–Cenomanian) were cored, and at Site 1213 a complete Berriasian–Hauterivian section was additionally recovered (Bralower, Premoli Silva, Malone, et al., 2002; Bown, this volume). The Shatsky Rise sites include a number of scientifically significant Cretaceous intervals, including four complete Cretaceous/Tertiary (K/T) boundary sections, four mid-Maastrichtian Event (MME) sections, three Oceanic Anoxic Event (OAE) 1a sections, and two OAE1b sections (Bralower, Premoli Silva, Malone, et al., 2002; Bown, this volume; Frank et al., 2005; Robinson et al., 2004).
This paper presents the results of shore-based calcareous nannofossil biostratigraphy of the Upper Cretaceous sites (1207–1213), represented by 409 samples. The paper particularly focuses on the Campanian– Maastrichtian interval that forms the bulk of the Upper Cretaceous sediments recovered during Leg 198. Nannofossil assemblages are abundant, diverse, and relatively well preserved throughout, but biostratigraphy is problematic in places due to missing or rare and sporadically distributed marker species. The assemblages are distinctly different in composition from those of the better known Atlantic Ocean and its marginal basins but show similarities with certain Indian Ocean nannofloras. Consequently, the sections provide important insights into the paleobiogeography and paleoecology of Late Cretaceous nannoplankton. The Lower to mid-Cretaceous nannofossil biostratigraphy (Berriasian–Cenomanian) is documented in Bown (this volume), the MME in Frank et al. (2005), and the K/T boundary section in Bown (in press) and Premoli Silva et al. (this volume).