Shatsky Rise is a moderate-sized large igneous province that erupted episodically at a hotspot triple-junction intersection between 146 and 133 Ma (Tithonian–Valanginian) at equatorial latitudes (Bralower, Premoli Silva, Malone, et al., 2002). Subsidence of the rise occurred soon after its construction, and Cretaceous water depths were probably on the order of 1.0–2.3 km (Bralower, Premoli Silva, Malone, et al., 2002). The sites were thus above the calcite compensation depth throughout the Cretaceous. Shatsky Rise was located close to the equator in the Early Cretaceous but drifted northward through the Late Cretaceous, and the cessation of chert deposition in the Campanian has been used to argue that Shatsky exited a broad, high-productivity equatorial divergence zone at this time (Bralower, Premoli Silva, Malone, et al., 2002).
Site 1207 is located on the previously undrilled Northern High, Site 1208 on the undrilled Central High, and Sites 1209–1214 on the Southern High of Shatsky Rise (Fig. F1). The Southern High was previously drilled during Deep Sea Drilling Project (DSDP) Legs 6, 32, and 86 and ODP Leg 132, with some Upper Cretaceous sediment recovered at Sites 47, 48, 305, 577, and 810. The Cretaceous sections recovered at all sites during Leg 198 were characterized by pure nannofossil ooze in the Campanian and Maastrichtian and chert with nannofossil ooze and porcellanite in the older Cretaceous sections. The presence of ubiquitous and abundant chert greatly affected core recovery below the Campanian (Bralower, Premoli Silva, Malone, et al., 2002). Nevertheless, almost every core produced some sediment, usually chert or porcellanite, accompanied by layers or vugs of variably lithified nannofossil-rich carbonate. Accordingly, a continuous nannoplankton record was generated through these intervals, but sample spacing is often limited to 9–10 m, and the paucity of carbonate sediment available generally prohibited the recovery of foraminifers (Bralower, Premoli Silva, Malone, et al., 2002).