As soon as a core is retrieved on deck, a sample is taken from the core catcher and given to the paleontological laboratory for an initial age assessment. Then the core is placed on a long horizontal rack, and gas samples may be taken by piercing the core liner and withdrawing gas into a vacuum tube. Voids within the core are sought as sites for gas sampling. Some of the gas samples are stored for shore-based study; however, others are analyzed immediately as part of the shipboard safety and pollution-prevention program. Next, the core is marked into section lengths, each section is labeled, and the core is cut into sections. Headspace gas samples are scraped from the ends of cut sections on the catwalk and sealed in glass vials for light hydrocarbon analysis. Each section is then sealed at the top and bottom by gluing on color-coded plastic caps, blue to identify the top of a section and clear to identify the bottom. A yellow cap is placed on the section ends from which a whole-round sample has been removed. The caps are usually attached to the liner by coating the end liner and the inside rim of the cap with acetone, and then the caps are taped to the liners. Additionally, during Leg 191, sediment samples were taken on the deck for microbiology studies. Special handling of these samples is specified in "Microbiology and Inorganic Geochemistry".
Next, the cores are carried into the laboratory, where the sections are labeled again, using an engraver to mark the full designation of the section permanently on the core liner. The length of the core in each section and the core-catcher sample are measured to the nearest centimeter; this information is logged into the shipboard CORELOG database program. After cores have equilibrated to room temperature (~3 hr), they are run through the multisensor track (MST), thermal conductivity measurements are performed on relatively soft sediments, and the cores are split.
Cores of soft material are split lengthwise into working and archive halves. The softer cores are split with a wire or saw, depending on the degree of induration. Harder cores are split with a band saw or diamond saw. During Leg 191, the wire-cut cores were split from the bottom to top; thus, investigators should be aware that older material may have been transported up the core on the split face of each section.
The working half of the core is sampled for both shipboard and shore-based laboratory studies. Each extracted sample is logged into the sampling computer database program by the location and the name of the investigator receiving the sample. Records of all removed samples are kept by the curator at ODP. The extracted samples are sealed in plastic vials or bags and labeled. Samples are routinely taken for shipboard physical properties analysis, magnetic studies, and for calcium carbonate (coulometric analysis) and organic carbon (CNS elemental analyzer) analyses.
The archive half is described visually (see "Sediment Description"). Smear slides are made from sediment samples taken from the archive half. Most archive sections are run through the archive multisensor track (AMST), for magnetic susceptibility and color reflectance spectroscopy measurements, and the cryogenic magnetometer. The archive half then is photographed using black-and-white and color film. Close-up photographs (color and black and white) are taken of particular features for illustrations in the summary of each site, as requested by individual scientists.
Both halves of the core then are placed into labeled plastic tubes, sealed, and transferred to cold-storage space aboard the drilling vessel. At the end of the leg, the cores are transferred from the ship in refrigerated airfreight containers to cold storage at ODP's Gulf Coast Repository at Texas A&M University.
Igneous rock cores are handled differently from sediment cores. Once on deck, 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 to the nearest centimeter. This information is logged into the shipboard CORELOG database program. The core then is cut into 1.5-m-long sections and transferred into the laboratory.
The contents of each section are transferred into 1.5-m-long sections of split core liner, where the bottom 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 is done to ensure that orientation is not lost during the splitting and labeling processes. Important primary features of the cores also are recorded at this time. The core then is split into archive and working halves. A plastic spacer is used to separate 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 groups of pieces are assigned the same number but are lettered consecutively. Pieces are labeled only on the outer cylindrical surfaces of the core. If the piece is oriented, an arrow is added to the label pointing to the top of the section. Because pieces are free to turn about a vertical axis during drilling, determination of azimuthal orientation during Leg 191 was possible only by using paleomagnetic or downhole logging data.
In splitting the core, every effort is made to ensure that important features are represented in both halves. The working half is sampled for shipboard physical properties measurements, magnetic studies, X-ray fluorescence (XRF), X-ray diffraction (XRD), and thin-section studies. Nondestructive physical properties measurements, such as magnetic susceptibility, are performed on the archive half of the core. Where recovery permits, samples are taken from each lithostratigraphic unit. Some of these samples are minicores. Records of all samples are kept by the curator at ODP. The archive half then is photographed using black-and-white and color film. Close-up photographs (color and black and white) are taken of particular features for illustrations in the summary of each site, as requested by individual scientists. Both halves of the core then 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 191 cores, they are housed at ODP's Gulf Coast Repository at Texas A&M University.