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doi:10.2204/iodp.proc.330.102.2012 Methods1Expedition 330 Scientists2ProceduresNumbering of sites, holes, cores, and samplesDrilling sites are numbered consecutively from the first site drilled by the D/V Glomar Challenger in 1968. Integrated Ocean Drilling Program (IODP) Expedition 301 began using the prefix “U” to designate sites occupied by the US Implementing Organization (USIO) vessel (the R/V JOIDES Resolution). 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 on. Three Expedition 330 sites have only one hole (A). Sites U1375 and U1377 have two holes (A and B). The cored interval is measured in meters below seafloor (mbsf). 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. During Expedition 330, all core depths below seafloor were calculated according to core depth below seafloor Method A (CSF-A) (see “IODP Depth Scales Terminology” at www.iodp.org/program-policies/). To more easily communicate shipboard results, all depths are reported in this volume as mbsf unless otherwise noted. 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. When applicable, attempts were made during Expedition 330 to core the uppermost soft-sediment succession using a gravity-push technique with little or no rotation of the rotary core barrel assembly. When formation resistance was felt (at varied depths), the core barrel was retrieved before drill string rotation was initiated. In addition, depending on recovery rate and penetration speed in the hard rock portion of the hole, the core barrel was occasionally retrieved after only ~5 m of penetration, yielding a half-core. 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 rock or sediment contained in a plastic liner (6.6 cm internal diameter) plus an additional ~0.2 m in the core catcher, which is a device at the bottom of the core barrel that prevents the core from sliding out when 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. In hard rock cores this typically occurs when a pedestal of rock fails to break off and is grabbed by the core barrel of the subsequent core. Recovered cores are divided into 1.5 m sections that are numbered serially from the top downward. When full recovery is obtained, the sections are numbered 1–7, with the last section usually being <1.5 m. Rarely, an unusually long core may require more than seven sections. When the recovered core is shorter than the cored interval, by convention the top of the core is deemed to be located at the top of the cored interval for the purpose of calculating (consistent) depths. When coring hard rocks, 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, hard rock material recovered from the core catcher is placed below the last section. In sedimentary cores, the core catcher section is treated as a separate section (“CC”). When the only recovered material is in the core catcher, it is placed at the top of the cored interval. A complete identification number for a sample consists of the following information: expedition, site, hole, core number, core type, section number, piece number (hard rock only), and interval in centimeters measured from the top of the section. For example, a sample identification of “330-U1372A-26R-3 (Piece 5, 40–47 cm)” indicates a 7 cm long sample of Piece 5 taken from the interval between 40 and 47 cm below the top of Section 3 of Core 26 (“R” means this core was taken with the rotary core barrel assembly) in Hole A at Site U1372 during Expedition 330. All cores were drilled with the rotary core barrel assembly during Expedition 330. Core handlingAll cores recovered during Expedition 330 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. Hard rock pieces were pushed to the bottom of the liner, and total rock length was measured by the curator on the catwalk. The length was entered into the database as “created length” using the Sample Master application. This number was used to calculate recovery. The plastic liner was then cut into ~1.5 m sections. Liner caps were placed at both ends of each section (blue = top end, colorless = bottom end). The 1.5 m sections were transferred to the core splitting room. For soft sediment, the plastic liners were split lengthwise to expose the core. Hard rock core pieces were slid out of the liners and placed in order in new, clean sections of core liner that had previously been split in half. Pieces having a vertical length greater than the internal (horizontal) diameter of the core liner are considered oriented pieces because they could have rotated only around their vertical axes. Those pieces were immediately marked on the bottom with a red wax pencil to preserve their vertical (upward) orientations. Pieces that were too small to be oriented with certainty were left unmarked. Adjacent but broken core pieces that could be fit together along fractures were curated as single pieces. The structural geologist on shift confirmed the piece matches and corrected any errors. The structural geologist also marked a split line on the pieces, which defined how the pieces should be cut into two equal halves. The aim was to maximize the expression of dipping structures on the cut face of the core while maintaining representative features in both archive and working halves. Microbiology samples from soft sediment were taken as whole-round samples on the catwalk by cutting a ~5 cm piece of liner from the end of the core, just above the core catcher. For hard rocks, whole-round samples were taken in the splitting room immediately after the core was slid from the liner. The petrologist on duty monitored the microbiology sampling to ensure that no critical petrographic interval was depleted. All microbiology whole-round samples were photographed from both sides. After microbiology sampling was completed, a plastic spacer was secured with acetone to the split core liner between individual pieces or reconstructed contiguous groups of subpieces (hard rock sections only). These spacers may represent a substantial interval of no recovery. The length of each section of core, including spacers, was then entered as “curated length” into the curation database. Curated length commonly differs by a few to several centimeters from the created length measured on the catwalk (depending on the number of pieces/spacers). Accordingly, the assumed depth of each piece is recalculated in the database on the basis of curated length, and all further observations and measurements are taken against this recalculated depth. Each section was allowed to equilibrate for ~3 h to ambient room temperature before being scanned using the shipboard Whole-Round Multisensor Logger (see “Physical properties”). The whole-round core sections were next measured with the Natural Gamma Radiation Logger (see “Physical properties”). Each piece of core was then split with a diamond-impregnated saw (for hard rocks) into an archive half and a working half, with the positions of plastic spacers between individual pieces maintained in both halves of the plastic liner. Pieces were numbered sequentially from the top of each section. Separate subpieces within a single piece were assigned the same number but were lettered consecutively (e.g., 1A, 1B, 1C). Pieces were labeled only on the outer cylindrical surfaces of the core. If it was evident that an individual piece had not rotated around a horizontal axis during drilling, an arrow pointing to the top of the section was added to the label. The oriented character of the piece was then recorded in the database using the Sample Master application. Digital images of the dry, cut faces of the archive halves were captured with the Section Half Imaging Logger (SHIL). Images were taken with a line scan camera at intervals of 20 pixels/mm. 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. Laser data (e.g., locations of core gaps and rubble intervals) were used to aid data filtering of the multisensor measurements (see “Physical properties”). The archive half of each core (soft sediment or hard rock) was described for lithologic, sedimentologic, magmatic, and volcanic features, and structural observations and alteration characteristics were noted. All observations were recorded in the Laboratory Information Management System (LIMS) database 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). Finally, digital color close-up images (both from dry and wet surfaces) were taken of particular features of the archive or working halves, as requested by individual scientists. During the crossover between night and day shifts, a sample meeting was held at 1200 h to discuss the sections described and to select key sampling intervals for shipboard analysis. Discrete samples were taken from working halves for shipboard physical property, paleomagnetic, thin section, X-ray diffraction (XRD), and geochemical analyses (e.g., inductively coupled plasma–atomic emission spectroscopy [ICP-AES]), as described in the sections below. Nondestructive X-ray fluorescence (XRF) analyses were also conducted on the working halves using a portable XRF instrument (see details in “Geochemistry”). Each sample was logged into the Sample Master application by location, sample type, and intended shipboard study (e.g., thin section, XRD, XRF, etc.). Paleomagnetic measurements with stepwise alternating-field demagnetization were conducted on oriented archive-half pieces (approved by the curator) to guide (and thereby minimize) paleomagnetic discrete sampling of the working halves. The microbiology whole-round samples taken on the catwalk (sediment) or in the splitting room (hard rock) were used both for shipboard and personal postcruise studies (see details in “Microbiology”). Residual material was returned to the curator and made available for additional shipboard or personal sampling. Records of all removed samples are kept by the IODP curator. Sampling for personal postcruise research was conducted during several sampling parties over the course of the expedition. At the end of Expedition 330, all cores were transferred from the ship for permanent storage at the IODP Gulf Coast Repository in College Station, Texas (USA). |
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