Site 1138, located north of Site 747 (Leg 120) on the Central Kerguelen Plateau (Fig. F2), reached nearly 900 meters below seafloor (mbsf), retrieving Cretaceous basement rock and ~700 m of sediment, mostly chalk, clay, and ooze. This study is based on 30 sediment samples, taken at a resolution of ~1 per section from Cores 183-1138A-12R to 20R from the single hole drilled at this site (Fig. F3). The samples range in depth from ~105 to 230 mbsf, an interval initially determined to be of late Miocene and younger age (Shipboard Scientific Party, 2000). The sediment, described on board as diatom clay, foraminifer-bearing nannofossil clay, and foraminifer-bearing nannofossil ooze, is also rich in radiolarians and other siliceous microfossils (Shipboard Scientific Party, 2000). The interval chosen for this study includes the lowermost part of lithologic Unit I (diatom clay in Core 183-1138A-12R) and the upper part of lithologic Unit II (nannofossil clay and ooze; Cores 183-1138A-13R to 20R). Recovery of sediments in this interval was only moderate (~50%) because of the use of rotary coring technology, which limits the resolution of any biostratigraphic study of the section.