Site 1143 (9.362°N, 113.300°E) was drilled during Ocean Drilling Program (ODP) Leg 184 in the southern SCS in a water depth of 2772 m (Fig. F1). The sediment thicknesses were 400 m in Hole 1143A, 258 m in Hole 1143B, and 500 m in Hole 1143C.
A total of 410 samples were investigated. Sample intervals were 0.2 m above 23.6 meters composite depth (mcd) and averaged 0.5 m from 23.7 to 95.3 mcd. One sample was taken per 9.6 m from 94 to 290.1 mcd, and one sample was taken per 1.5 m from 290.1 to 513 mcd.
Every sample was dried, weighed to yield 1 g, and then treated with 10% hydrochloric acid to remove the calcium carbonate. The acid was removed with deionized water; 10% hydrogen peroxide was added; and the sample was boiled for 30 min to remove organic matter, cleaned, and dried. Diatoms were concentrated in a heavy liquid with a density of 2.4, and the heavy liquid was removed by rinsing with deionized water. The concentrated diatoms were then spread on a 20 mm x 20 mm coverslip, dried on a hot plate, and mounted in Canada balsam.
More than 200 specimens were counted and identified at a magnification of 600x, and a smaller number of specimens were identified at 1000x. The entire microscope slide was scanned if diatom specimens were absent or numbered <200. Identification of marker species for the stratigraphy is based on Akiba and Yanagisawa (1986) and Schrader (1973). Biostratigraphic zones were selected from Barron (1985a, 1985b) (Fig. F2). A total of 150 species from 55 genera were identified. The abundance of each species and the total abundance of diatoms for every sample are listed in Table T1 and are shown in Figures F3 and F4.