The standard zonal scheme of Okada and Bukry (1980), with some additional bioevents, was applied to Leg 189 Miocene sediments (Fig. F2). Several low-latitude species used as zonal markers by Okada and Bukry (1980) are rare to absent in Leg 189 sediments, which forced the combination of several zones. Additional Miocene biostratigraphic events have been recognized by many workers (Raffi et al., 1995, 1998; deKaenel and Villa, 1996; Backman and Raffi, 1997; Maiorano and Monechi, 1998), and some of these events were included to improve biostratigraphic resolution and estimate zonal boundaries where marker species were absent.