Sediment samples were taken at each proposed drill site to characterize the nature of the seafloor and shallow subsurface, using pipe dredges, chain dredges, a Van-Veen grab, and a 1-ton gravity corer with 10-cm-diameter barrels. Gravity cores collected during the cruise were examined on a Geotek multisensor track at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, prior to splitting. This instrument measures gamma ray attenuation (GRA) bulk density, P-wave velocity, and magnetic susceptibility. Data were empirically calibrated using aluminum and water standards.
After measuring physical properties, core liners were cut in two halves and examined visually. Sediment color was determined using a color chart, major lithologies were recorded using the Dunham classification of carbonates as modified by Embry and Klovan (1971), and primary sedimentary structures were indicated (Heck et al., 1999). Smear slide analysis was used to determine grain and mud content of the sediment. Nannofossils from three cores were studied to obtain age information of the cored sediments at an average frequency of four to five smear slides per core. Smear slides were examined visually with a microscope at 1000x magnification. Nannofossils were identified and counted on a randomly chosen 40-mm-wide band. A total number of 100 fossils per slide was counted.
Total carbon and inorganic carbon (IC) contents were measured using a CO2 coulometer attached to either an autosampler furnace for total carbon or an acidification module for inorganic carbon. Bulk sediment was powdered using an agate mortar, and 12 mg was placed into 0.15-mL Sn capsules. Samples were loaded into an autosampler wheel, where they were combusted at 950°C.
Sample acidification was performed with HClO4 (2 N) and measured according to standard coulometric techniques (see Shipboard Scientific Party, 2002). IC was subtracted from total carbon to obtain total organic carbon (TOC) concentrations. With the coulometric methods described above, a standard deviation of 0.2 wt% was obtained both for IC and TOC content. A fingertip of the dried powdered sediment prepared for coulometric analysis was used for stable isotope measurement. Carbonate isotope standards are measured with a typical standard deviation of 0.06‰.