The samples studied are mainly clays from a ~479-m-thick section of cores recovered from Holes 1148A and 1148B (Sections 184-1148A-40X-1 through 76X-6 and 184-1148B-39X-CC through 56X-1).
Sampling intervals at Site 1148 are ~2–3 m, and 289 samples were processed. However, because of time constraints, only 105 samples were investigated microscopically. Each dried sample, weighing ~10 g, was processed at the Key Laboratory of the Ministry of National Education, Tongji University, using standard palynological processing (Wood et al., 1996). Maceration was achieved using hydrochloric acid (10%) and dissolution in concentrated hydrofluoric acid (40%, cold). Oxidation with nitric acid or Schulze's solution was omitted to avoid damage to delicate cysts. No heavy liquid separation was applied because of the small amounts of residue remaining after acid maceration. Instead, a Nitex sieve of 7 µm mesh size, coupled with ultrasonic vibration technique, was used to remove tiny inorganic particles. Exotic Lycopodium spores were added to the samples before acid maceration to allow calculation of dinoflagellate concentration (abundance). Permanent slides, made with glycerin jelly with a wax seal, are stored in the Key Laboratory of the Ministry of National Education, Tongji University.
Microscopic investigation for each sample was commonly carried out on one to two permanent slides (each slide with two 20-mm x 20-mm coverslips). Abundance of dinoflagellate cysts was determined by the number of dinoflagellate cysts recorded in casual scanning when 200 exotic Lycopodium spores were encountered. The same method was used for other palynomorphs (Table T1). However, for samples in which dinoflagellate cysts are very rare, it was necessary to scan four to five slides in order to document more representative assemblages. In such cases, the number of cysts registered may be smaller than the total number of species observed in a given sample. Relative abundance of each taxon is designated by the following ranking:
"P" indicates "present" when the total counts of dinoflagellate cysts/200 grains of exotic Lycopodium spores are <50 (Table T2). Unless specified otherwise, the dinoflagellate cyst taxonomy used in the present work follows the Lentin and Williams Index of Fossil Dinoflagellates (Williams et al., 1998), in which the full citations and authorships can be found.