The "Explanatory Notes" chapter documents the procedures and methods employed in the various shipboard laboratories during Leg 209. This information concerns only shipboard methods described in the Leg 209 Initial Reports volume of the Proceedings of the Ocean Drilling Program (ODP). Methods for shore-based analysis of Leg 209 samples and data will be described in the individual scientific contributions to be published in scientific journals and in the Leg 209 Scientific Results volume.
All shipboard scientists contributed to the completion of this volume. The separate sections of the chapters were, however, written by groups of scientists as given below (listed alphabetically):
- Leg Summary: Shipboard Scientific Party
- Background and Objectives: Kelemen, Kikawa
- Operations: Miller, Storms
- Igneous Petrology: Abe, Cipriani, Meurer, Seyler, Takazawa
- Metamorphic Petrology: Bach, Garrido, Harvey, Paulick, Rosner
- Structural Geology: Casey, Cheadle, Dick, Faul, Schroeder
- Geochemistry: Chambers, Godard, Graham
- Physical Properties: Carlson, Ildefonse
- Paleomagnetism: Garces, Gee
- Microbiology: Griffin, Josef
- Downhole Measurements: Iturrino
Drilling sites are numbered consecutively from the first site drilled by the Glomar Challenger in 1968. At a site, multiple holes can be drilled by removing the drill pipe from the seafloor, moving the ship a short distance, and then drilling a new hole. For all ODP 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 suffix "B," and so forth.
The cored interval is measured in meters below seafloor (mbsf). The depth below seafloor is determined by subtracting the water depth estimated from the initial drill pipe measurement, which gives the length of pipe from the rig floor to the seafloor (measured in meters below rig floor [mbrf]), from the total drill pipe measurement. During most ODP cruises, each cored interval is generally 9.5–9.6 m long, which is the length of a core barrel. However, one potential cause of poor recovery in hard rock coring is core jamming in the bit or the throat of the core. To enhance recovery, most cored intervals during Leg 209 were reduced to 4.5–5 m (half cores). A recovered core is divided into 1.5-m sections that are numbered serially from the top. When full recovery is obtained, the sections are numbered sequentially as recovered starting with 1 at the top of the core; the last section may possibly be shorter than 1.5 m (Fig. F1).
When the recovered core is shorter than the cored interval, the top of the core is equated with the top of the cored interval (in mbsf) by convention to achieve consistency in handling analytical data derived from the cores. Samples removed from the cores 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, piece number (for hard rock), and interval in centimeters measured from the top of section. For example, a sample identification of "209-1268A-2R-2, 30–32 cm" would represent a piece of core removed from the interval between 30 and 32 cm below the top of Section 2, Core 2 (R designates that this core was taken with the rotary core barrel) of Hole 1268A from Leg 209 (Fig. F1).
In rare cases, coring intervals were repeated when the bit failed to reach the bottom of the hole after a core was recovered. Since the rock recovered in these instances represented no new penetration, the core designator "M" was assigned. Cores recovered with the logging-while-coring assembly were assigned the core designator "A."
At the start of coring operations, we elected not to use plastic liners in the core barrels because of concern that fragments of core might jam in the liner, thus limiting recovery. During operations at Site 1272, we recovered a few cores with plastic liners and noted higher average recovery than we had achieved without liners in similar lithologies. All cores recovered at Sites 1273, 1274, and 1275 were therefore collected in plastic liners.
For cores recovered without plastic liners, core pieces were transferred to clean, labeled split core liners in the core splitting room. The top of the core was marked with a blue liner cap, and colorless liner caps were glued to the bottom of liner sections. When cores were recovered in plastic liners, liner caps (blue = top) were glued onto liner sections on the catwalk after splitting the liner into 1.5-m sections. The 1.5-m sections were transferred to the core splitting room, where the plastic liners were split lengthwise.
Nearly all pieces were marked with a red wax pencil before they were extracted from the core barrel or removed from the split core liner to preserve orientation. In some cases, the pieces were too small to be certain of orientation. Therefore, the red wax mark does not universally indicate that the core piece was oriented.
Pieces of the core were pushed together and the length of the core in each split core liner was measured to the nearest centimeter; this measurement was entered into the ODP curation data acquisition program. Whole-round samples for microbiology were sampled in the core splitting room prior to any other handling using techniques described in "Microbiology".
Core pieces that could be fit along fractures were curated as single pieces with letter suffix designations as subpieces. A plastic spacer was secured to the split core liner with acetone between individual pieces and/or reconstructed contiguous groups of pieces. These spacers may represent a substantial interval of no recovery.
The length of each section of core including spacers was entered into the curation database as the curated length. The curated length will commonly differ by a few centimeters from the liner length measured on the catwalk. Subsequently, the cores were marked by a structural geologist to indicate a split line, ideally maximizing the expression of dipping fabric (i.e., perpendicular to foliation) on the cut face of the core. The outer cylindrical surfaces of the whole-round pieces were scanned with the ODP digital core scanner, using the split line marking for registration. Each section was scanned using the shipboard multisensor track (MST) (see "Nondestructive Tests" in "Physical Properties"). Each piece of core was then split into archive and working halves, with the positions of spacers maintained for both halves. Pieces are 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.
The archive half of each core was described, and observations were recorded on ODP templates and spreadsheets developed by the shipboard scientific party (for details see individual disciplinary sections in this chapter). Digital images of the archive halves were made on the ODP digital imaging system. Archive-half sections were also passed through the cryogenic magnetometer for magnetic remanence measurements. Finally, the archive half was photographed using black-and-white and color film. Close-up photographs (color and black and white) were taken of particular features for illustrations in the summary of each site, as requested by individual scientists.
The working half of the core was sampled for both shipboard and shore-based laboratory studies. Samples were routinely taken for shipboard physical properties; paleomagnetic, thin section, and geochemical analyses; and microbiological and molecular investigations, as described in the sections to follow. Each extracted sample was logged into the sampling database program by the location and the name of the investigator receiving the sample or by the type of shipboard sample. Records of all removed samples are kept by the curator at ODP. The extracted samples were sealed in plastic vials, cubes, or bags and labeled.
Following the shipboard initial scientific measurements and sampling, both halves of cores were shrink-wrapped in plastic to prevent rock pieces from moving out of sequence during transit. The working and archive halves of cores were then put into labeled plastic tubes, sealed, and transferred to cold-storage space aboard the drilling vessel. At the end of Leg 209, the cores were transferred from the ship to cold storage at the ODP Repository in Bremen, Germany.
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.
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