Site 1219 is located at 7°48.019´N, 142°00.940´W, 3° north of the Clipperton Fracture Zone (Fig. F1). The drill site represents the southernmost location of a north–south oriented transect drilled on 56-Ma crust. The distance from Site 1219 northward to Site 1220 is ~400 km, and the distance to Leg 8 Sites 70 and 71 is ~300–400 km (Tracey, Sutton, et al., 1971).
Site 1219 was evidently situated in the southern hemisphere until 29 Ma (late Oligocene equator crossing); equatorial and tropical conditions existed there between the middle Eocene and the early Miocene (Shipboard Scientific Party, 2002). These conclusions are based on reconstruction of equator passage and paleogeographic position using a fixed hotspot model (Gripp and Gordon, 1990; Engebretson et al., 1985).
Site 1219 sediments contain numerous levels of diatom-bearing sediments that are related to the high-productivity events at 40 Ma and during the equator passage (Fig. F2). Neighboring sites are not included in this pilot study, either because of the scarcity of diatoms in the smear slides from Site 1220 or because of the poor sediment recovery at neighboring sites. Floral and faunal changes in the corresponding diatom-rich unit at Site 1218 will be compared with the present results in a separate study.