Drilling 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 one acoustic beacon. 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. Each cored interval is generally 9.5 m long, which is the length of a core barrel. Cored 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 one through seven, with the last section possibly being shorter than 1.5 m (Fig. F1); rarely, an unusually long core may require more than seven 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 sediment 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, piece number (for hard rock), and interval in centimeters measured from the top of section. For example, a sample identification of "191-1179C-3H-5, 80-85 cm" would be interpreted as representing a sample removed from the interval between 80 and 85 cm below the top of Section 5, Core 3 (H designates that this core was taken during hydraulic piston coring) of Hole 1179C from Leg 191 (Fig. F1).
All ODP core identifiers indicate core type. The following abbreviations are used: