3. Explanatory Notes¹

Shipboard Scientific Party²

INTRODUCTION

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 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):

Principal Results: Shipboard Scientific Party

Operations: Pettigrew, Klaus

Lithostratigraphy: Fergusson, Hirano, Stuerer, Wilson, Underwood

Structural Geology: Maltman, Morgan, Sanchez-Gomez, Tobin, Ujiie

Biostratigraphy: Boeckel

Paleomagnetism: Dean, Hisamitsu

Inorganic Geochemistry: Kastner, Spivack

Organic Geochemistry: L. Becker

Microbiology: Cragg, Murakami, Smith

Physical Properties: Henry, Hunze, Saffer, Screaton

Downhole Measurements: Tobin

In Situ Temperature Measurements: K. Becker, Screaton

Seismic Stratigraphy: Moore

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 "190-1173B-26R-2, 20-25 cm" represents a sample removed from the interval between 20 and 25 cm below the top of Section 2. Core 26R designates that this core was taken during rotary core barrel coring of Hole 1173B from Leg 190.

All ODP core identifiers indicate core type. The following abbreviations are used: H = advanced hydraulic piston corer (APC); X = extended core barrel (XCB); R = rotary core barrel (RCB).

As soon as a core is retrieved on deck, a sample is taken from the core catcher and, if sedimentary, given to the paleontological laboratory for an initial age assessment. 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, cut out of the core, and then the section are cut. When possible, these samples are taken from the bottom of sections. During Leg 190, whole-round samples were taken for interstitial water (IW) 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 by 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) is written on the yellow cap. The core sections are then carried into the laboratory, and the length of the core sections and any samples taken are logged into the shipboard database.

After the core sections equilibrate to ambient lab temperature (~3 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, paleomagnetism, magnetic susceptibility, and color reflectance. Samples were taken from the working half for shipboard physical properties 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 the Gulf Coast Repository of the Ocean Drilling Program (ODP) in College Station, Texas.