Sediments were stored at <0°C prior to freeze-drying and homogenization. Aliquots of the dry sediment were taken for total carbon (TC) and sulfur (TS) analysis using a Leco carbon analyzer. A further aliquot of dry sediment was fired to remove organic carbon (500°C for 24 hr) and carbon content determined to give total inorganic carbon (TIC). It is assumed that all inorganic carbon consists of calcite so that CaCO3 = TIC × 8.3334. Organic carbon content (Corg) was determined by difference (Corg = TC - TIC). Further aliquots of dry sediment (~3 g) had a known quantity of an internal standard (n-C36 alkane) added for later quantification and were extracted into dichloromethane/methanol (3:1) (6 × 3 mL extractions) with ultrasonication (15 min). Samples were centrifuged following each extraction and decanted. Combined extracts were dried under N2 onto silica (0.5 g; 70-230 mesh) ready for column chromatography.
Column chromatography was conducted on each sample after the methods of Peltzer et al. (1984). The column was packed with deactivated (5%) silica (7 g of 70-230 mesh in a 9-mm internal diameter [ID] column) in hexane. Four fractions were collected following elution with (1) hexane (20 mL), (2) hexane/toluene (4:1; 30 mL), (3) hexane/ethyl acetate (37:3; 40 mL), and (4) hexane/ethyl acetate (4:1; 40 mL). Excess solvent was removed by rotary evaporation and fractions were transferred in dichloromethane to vials, dried under N2, and stored at ~4°C until analysis.
Fractions 1-3 were analyzed directly without prior derivatization. Fraction 4 contained alcohol and acid moieties that were derivatized to their trimethylsilyl ethers with bis-(trimethylsilyl) trifluoroacetamide (BSTFA) in dichloromethane (100 µL of each at 70°C for 2 hr in N2-purged vials). Quantification was made by gas chromatography with on-column injection and flame ionization detection (GC-FID) using an HP1 fused silica capillary column (60 m × 0.32 mm ID). Hydrogen was used as a carrier gas and the oven temperature program was 45° to 145°C at 10°C/min and 145° to 305°C at 4°C/min. Data acquisition and integration were made with an Atlas data system. Gas chromatography-mass spectrometry was performed using a Hewlett-Packard 5972 quadrapole mass spectrometer. Split-splitless injection was used with an HP1 fused silica capillary column (30 m × 0.32 mm ID; the subsequent loss of resolution by using a shorter column was compensated by minimizing column bleed above 280°C). Helium was used as a carrier gas with the same oven-temperature program as used for GC-FID. The mass spectrometer was operated in electron impact (ionizing energy of 70 eV; ion source temperature of 250°C) with a scan time (m/z 50-600) of 1 s. Compound identification was made by comparing mass spectra with authentic standards, literature sources, and relative retention times.
Mass accumulation rates were calculated as in Emeis et al. (1995) from gamma-ray attenuation porosity evaluator-derived dry-bulk densities (from Wefer, Berger, Richter, et al., 1998) and linear sedimentation rates (calculated from the biostratigraphic age model in Wefer, Berger, Richter, et al., 1998).