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Expedition 323 Scientists2
Background and objectives
This chapter documents the procedures and methods employed in the shipboard work described in the Expedition Reports section of the Expedition 323 Proceedings of the Integrated Ocean Drilling Program volume. Methods for shore-based analysis of Expedition 323 samples and data will be described in individual scientific contributions to be published elsewhere. All shipboard scientists contributed to the completion of this volume.
Numbering of sites, holes, cores, and samples
Drilling sites are numbered consecutively beginning with the first site drilled by the Glomar Challenger in 1968. Integrated Ocean Drilling Program (IODP) Expedition 301 began using the prefix "U" to designate sites occupied by a U.S. Implementing Organization (USIO) vessel. For all IODP drill sites, a letter suffix distinguishes each hole drilled at the same site. The first hole drilled is assigned the site number modified by the suffix "A," the second hole takes the site number and the suffix "B," and so forth.
The cored interval is measured in meters below seafloor according to the core depth below seafloor, appended (CSF-A), depth scale (see "IODP depth scales terminology" at www.iodp.org/program-policies/). This depth scale is equivalent to the Ocean Drilling Program (ODP) depth scale meters below seafloor (mbsf) (see "Core depth below seafloor (CSF-A)" in "Stratigraphic correlation"). In general, depth below seafloor is determined by subtracting the water depth estimated from the initial drill pipe measurement to the seafloor from the total drill pipe measurement. The depth interval assigned to an individual core begins with the depth below seafloor at which coring began and extends to the depth to which coring advanced. Each coring interval is generally ≤9.5 m, which is the length of a core barrel; however, coring intervals may be shorter.
Cores taken from a hole are numbered sequentially from the top of the hole downward. Core numbers and their associated cored intervals are unique in a given hole. Generally, maximum recovery for a single core is 9.5 m of sediment in a plastic liner (6.6 cm internal diameter) plus ~0.2 m (without a plastic liner) of sediment in the core catcher, a device at the bottom of the core barrel that prevents the core from sliding out while the barrel is retrieved from the hole. In certain situations, recovery may exceed the 9.5 m maximum. In soft sediments, this is normally caused by core expansion resulting from depressurization.
Recovered cores are divided into 1.5 m sections that are numbered serially from the top. When full recovery is obtained, these sections are numbered from 1 to 7, with the last section usually being shorter than 1.5 m. Rarely, an unusually long core may require more than seven sections. When a recovered core is shorter than the cored interval, the top of the core is equated with the top of the cored interval by convention to achieve consistency in handling analytic data derived from the cores. All pieces recovered are placed immediately adjacent to each other in the core tray. Samples and descriptions of cores are designated by distance, measured in centimeters from the top of the section to the top and bottom of each sample or interval. By convention, when a core is described, material recovered from the core catcher is placed below the last section and labeled with the suffix "CC." In sedimentary cores, core catcher sections are treated as separate sections. The core catcher is placed at the top of the cored interval when material is recovered only in the core catcher. However, information supplied by the drillers or logging may allow more precise interpretation of the correct position of core catcher material within an incomplete recovered core interval.
Complete sample identification numbers include the following information: expedition, site, hole, core number, core type, and section number, with the interval in centimeters measured from the top of the section. For example, the sample identification "323-U1339A-26H-8, 4–7 cm" indicates a 3 cm sample removed from the interval between 4 and 7 cm below the top of Section 8 of Core 26 ("H" designates that this core was taken with the advanced piston corer [APC]) in Hole A at Site U1339 during Expedition 323.
Cores recovered during Expedition 323 were extracted from the core barrel in plastic liners. These liners were carried from the rig floor to the core processing area on the catwalk outside the core laboratory, where they were split into ~1.5 m sections. Liner caps (blue = top; colorless = bottom) were glued with acetone onto liner sections on the catwalk by the curator. The length was entered into the database as "created length" using the Sample Master application. This number was used to calculate recovery.
Each section was allowed to equilibrate to ambient room temperature (4 h for sediment) and scanned with the shipboard Whole-Round Multisensor Logger (WRMSL) (see "Physical properties"). Whole-round core sections were then measured with the Natural Gamma Radiation Logger (NGRL) (see "Physical properties") and transferred to the core splitting room, where the plastic liners were split lengthwise into archive and working halves.
The archive halves were described for lithology and structural features, and observations were recorded using the descriptive data capture application, DESClogik. Specialized templates and spreadsheets were developed for this application by the individual descriptive laboratory groups (for details, see individual disciplinary sections in this chapter). Digital images of the cut faces of the archive halves were captured with the Section Half Imaging Logger (SHIL). Measurements of point magnetic susceptibility and color reflectance were performed with the Section Half Multisensor Logger (SHMSL) on the archive halves. This instrument also includes a laser calibration system. Data from the laser (e.g., the location of core gaps and rubble intervals) were used to aid data filtering of multisensor measurements (see "Physical properties").
Finally, digital color close-up photographs were taken of particular features, as requested by individual scientists. The working halves were sampled for both shipboard core characterization and shore-based studies.
Samples were taken from the working halves for shipboard physical properties, paleomagnetism, thin section, X-ray diffraction (XRD), and geochemical analyses, as described below. Each extracted sample was logged in the Sample Master database program by location, sample type, and intended shipboard study (e.g., thin section, XRD, etc.). Records of all removed samples are kept by the IODP Curatorial Specialist. At the end of Expedition 323, all cores were transferred from the ship for permanent storage at the Kochi Core Center at Kochi University, Japan. A postexpedition sampling party was organized and carried out at the Kochi Core Center to take the bulk of personal samples requested by members of the science party.