This chapter includes information on shipboard methods that will help the reader understand the basis for our preliminary interpretations and also help the interested investigator select samples for further analysis. Coring techniques and core handling, including the numbering of sites, holes, cores, sections, and samples (Fig. F1), are the same as those reported in previous Initial Reports volumes of the Proceedings of the Ocean Drilling Program (ODP) and are only briefly summarized.
The separate sections of the site chapters were written by the following shipboard scientists (authors are listed in alphabetical order; no seniority is implied):
Seafloor depths and cored intervals below seafloor (meters below seafloor [mbsf]) are determined by drill pipe measurement.
Drill sites are numbered consecutively from the first site drilled by the Glomar Challenger in 1968. A site refers to one or more holes drilled while the ship was positioned over a single acoustic beacon. The first hole drilled at a given site is assigned the site number modified by the suffix "A," the second hole takes the site number and suffix "B," and so forth. These suffixes are assigned regardless of recovery, as long as penetration takes place.
Each cored interval is generally 9.5 m long, which is the length of a core barrel. Coring intervals may be shorter and may not necessarily be adjacent if separated by intervals drilled but not cored. The depth interval assigned to an individual core begins with the depth below the seafloor at which the coring operation began and extends to the depth that the coring operation ended for that core.
A recovered core is typically divided into 1.5-m-long sections that are numbered serially from 1 through 7 (or less if partial recovery) beginning at the top. When the recovered core is shorter than the cored interval, the top of the core is equated with the top of the cored interval by convention in order to achieve consistency in handling analytical data derived from the cores. Also by convention, material recovered from the core catcher is placed in a separate section during the core description, labeled core catcher (CC), and placed below the last (bottom) section recovered in the liner. The core catcher is placed at the top of the cored interval in cases where material is only recovered in the core catcher.
Samples removed from a core section are designated by distance measured in centimeters from the top of the section to the top and bottom of each sample removed from that section. A full identification number for a sample consists of the following information: leg, site, hole, core number, core type, section number, and top to bottom interval in centimeters measured from the top of section. For example, a sample identification of "205-1253A-4R-2, 20-22 cm" represents a sample removed from the interval between 20 and 22 cm below the top of Section 2. Core 4R designates that this core was taken during rotary core barrel coring of Hole 1253A from Leg 205.
All ODP core identifiers indicate core type. The following abbreviations are used:
As soon as a core is retrieved on deck, the core liner with the core inside is marked into section lengths, each section is labeled, and the core is cut into sections. If a whole-round sample is to be taken, the desired interval is identified and cut out of the core, and then the section is cut. When possible, these samples are taken from the bottom of sections. During Leg 205, whole-round samples were taken for interstitial water analyses, organic geochemistry, and microbiology as well as for postcruise permeability and consolidation/strength measurements. For safety monitoring, small (~5 cm3) plugs of sediment are taken from the end of one section per core for headspace gas analysis. If pockets of gas are present, a vacutainer gas sample is taken through the core liner.
Each section is then sealed at the top and bottom using acetone to seal color-coded plastic caps to the plastic core liner. A blue end cap marks the top of a section, a clear cap marks the bottom, and a yellow cap marks the end of a section from which a whole-round sample has been removed. The sample code (e.g., IW for interstitial water) is written on the yellow cap. The core sections are then carried into the laboratory, and the length of the core sections (recovery) and any samples taken are logged into the shipboard database.
After the core sections equilibrate to ambient laboratory temperature (~2-4 hr), they are run through the multisensor track (MST). For soft sediments, thermal conductivity measurements are then made (see "Physical Properties"). Cores are subsequently split lengthwise into working and archive halves. The archive half is used for nondestructive measurements: visual core description, digital core imaging, paleomagnetism, magnetic susceptibility, and color reflectance. Samples are taken from the working half for shipboard physical property measurements (see "Physical Properties") before being sampled for additional shipboard and postcruise studies. The archive halves were photographed a whole core at a time, and close-up photographs were taken as requested. Finally, the core sections were put into labeled plastic tubes, sealed, and transferred to cold-storage space aboard the drilling vessel. Following the cruise, the cores were transported to ODP's Gulf Coast Repository in College Station, Texas. We did not sail a shipboard micropaleontologist during Leg 205. Samples were taken for postcruise biostratigraphy and will be integrated into the Scientific Results volume.
Igneous rock cores are handled differently from sedimentary cores. To minimize contamination of cores with platinum-group elements and gold, we requested that scientists and technicians remove all jewelry from their hands and wrists before handling the core on the core-receiving platform and wear latex gloves to minimize microbial contamination. Once on deck, samples for microbiological studies are taken immediately to minimize contamination. Then, the core catcher sample is placed at the bottom of the core liner, and total core recovery is calculated by pushing the rock pieces together and measuring the total length to the nearest centimeter. This information is logged into the shipboard CORELOG database program. Then the core is cut into 1.5-m-long sections and transferred to the laboratory.
The contents of each section are transferred into 1.5-m-long sections of split-core liner, where the bottoms of oriented pieces (i.e., pieces that clearly could not have rotated top to bottom about a horizontal axis in the liner) are marked with a red wax pencil. This ensures that orientation is not lost during splitting and labeling. Important primary features of the cores are recorded at this time. The core then is split into archive and working halves. A plastic spacer separates individual pieces and/or reconstructed groups of pieces in the core liner. These spacers may represent a substantial interval of no recovery. Each piece is numbered sequentially from the top of each section, beginning with number 1; reconstructed pieces are all assigned the same number but with a consecutive suffix letter (e.g., Piece 1A, 1B, etc.). Pieces are labeled only on the outer cylindrical surfaces of the core. If the piece is oriented, an arrow pointing to the top of the section is added to the label. Because pieces are free to rotate about a vertical axis during drilling, relative azimuthal orientation during Leg 205 was possible only by using paleomagnetic data. Prior to splitting the core, it is run through the MST system.
In splitting the core, every effort is made to ensure that important features are represented in both halves. The archive half is described visually. Most archive sections are run through the cryogenic magnetometer, except for cores with pieces that are too short or disrupted. The archive halves are then photographed with both black-and-white and color film, one core at a time. Nondestructive physical property measurements, such as magnetic susceptibility, are also performed on the archive half of the core. The working half is sampled for shipboard physical property measurements, paleomagnetic studies, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction, and thin section studies. Once the macroscopic description and shipboard analyses are fully integrated, the working half of the hard rock core is sampled for shore-based laboratory studies. After samples are taken, both halves of the core are shrink-wrapped in plastic to prevent rock pieces from vibrating out of sequence during transit, placed into labeled plastic tubes, sealed, and transferred to cold-storage space aboard the drilling vessel. As with the other Leg 205 cores, they are housed at ODP's Gulf Coast Repository at Texas A&M University.
1Examples of how to reference the whole or part of this volume can be found under "Citations" in the preliminary pages of the volume.
2Shipboard Scientific Party addresses can be found under "Shipboard Scientific Party" in the preliminary pages of the volume.
Ms 205IR-103