In this chapter, we have assembled information that documents our scientific methods. This information concerns only shipboard methods described in the site reports in the Leg 178 Initial Reports volume of the Leg 178 Proceedings of the Ocean Drilling Program (ODP). Methods for shore-based analysis of Leg 178 data will be described in the individual scientific contributions to be published in scientific journals and in the Scientific Results volume. Coring techniques and core handling, including the numbering of sites, holes, cores, sections, and samples, were the same as those reported in previous Initial Reports volumes of the Proceedings of the Ocean Drilling Program (e.g., Shipboard Scientific Party, 1998b).
Site chapters should be treated as a publication contributed by all the scientists listed at the front of this volume. Each scientist, however, had one or more areas in which he or she was one of the primary contributors. These are listed below (authors are listed in alphabetical order; no seniority is necessarily implied):
- Principal Results: Barker, Camerlenghi
- Background and Scientific Objectives: Barker, Camerlenghi
- Operations: Acton, Grout
- Lithostratigraphy: Cowan, Daniels, Escutia, Eyles, Maldonado, Pudsey, Wolf-Welling
- Biostratigraphy: Iwai, Osterman, Weinheimer, Winter
- Paleomagnetism: Acton, Brachfeld, Guyodo
- Organic Geochemistry: Sjunneskog
- Inorganic Geochemistry: Kyte, Schuffert
- Physical Properties: Barker (heat flow), Evans, Moerz, Vigar
- Composite Depths: Iorio
- Sedimentation Rates: Brachfeld, Iwai, Weinheimer, Winter
- Seismic Stratigraphy: Escutia, Moerz
- Downhole Measurements: Lauer, Moerz, Williams
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. 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 drilled intervals.
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 from 1 to 7; the last section may be <1.5 m (rarely, an unusually long core may require >7 sections). When less than full recovery is obtained, there will be as many sections as needed to accommodate the length of the core recovered. By convention, material recovered from the core catcher of a sedimentary core is placed in a separate section during the core description, labeled core catcher (CC), and placed below the last 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.
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, 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, and interval in centimeters measured from the top of section. For example, a sample identification of "178-1096A-3H-1, 10-12 cm" would be interpreted as representing a sample removed from the interval between 10 and 12 cm below the top of Section 1, Core 3 (H designates that this core was taken during hydraulic piston coring) of Hole 1096A from Leg 178.
All ODP core identifiers indicate core type. The following abbreviations are used: H = hydraulic piston core (HPC; also referred to as APC, or advanced hydraulic piston core); X = extended core barrel (XCB); R = rotary core barrel (RCB); and M = miscellaneous material.
As soon as a core is retrieved on deck, it goes through a sequence of processing steps. First, a sample is taken from the core catcher and given to the paleontological laboratory for an initial age assessment. The core is then placed on a long horizontal rack, and gas samples may be taken by piercing the core liner and withdrawing gas into a vacuum tube ("Vacutainer"). Voids within the core are sought as sites for gas sampling. Next, the core is marked into section lengths, each section is labeled, and the core is cut into sections. Interstitial water (IW) whole-round samples are then taken as a matter of ODP policy (typically on every third core); whole-round samples for organic geochemistry may also be taken at this stage if they have been requested. After initial IW and gas samples had been collected during Leg 178, small holes were drilled into the core liners for some of the cores to allow gas to escape.
Each section is then sealed at the top and bottom by attaching color-coded plastic caps, blue to identify the top of a section and clear for the bottom. A yellow cap is placed on the section ends from which a whole-round sample has been removed, and the sample code (e.g., IW) is written on the yellow cap. The caps are usually attached to the liner by coating the end liner and the inside rim of the cap with acetone (or a mixture of acetone and propanol), and then the caps are taped to the liners. The core sections are then carried into the laboratory, where the individual sections are again labeled using an engraver to mark permanently the full designation of the section. 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 JANUS database.
Cores of soft material are split lengthwise into working and archive halves. The softer cores are split using a wire or saw, depending on the degree of induration. Harder cores are split using a band or diamond saw. The wire-cut cores are split from bottom to top; thus, investigators should be aware that older material could have been transported up the core on the split face of each section. Following the initial scientific measurements, both halves of the core are put into labeled plastic tubes, sealed, and transferred to cold-storage space aboard the drilling vessel. At the end of Leg 178, the cores were transferred from the ship in refrigerated containers to cold storage at the ODP Core Repository in Bremen, Federal Republic of 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 "Leg 178
Participants" in the preliminary pages of the volume.
Ms 178IR-104