Appendix B: Core Curation Terms and Definitions³⁴

In this appendix, ODP-related curatorial terms, concepts and requirements are defined and explained.

The "scientific party" includes all scientists who sail on the leg, as well as any shore-based scientists who were granted permission from the SAC to receive samples or data from the leg within the moratorium.

The period from the beginning of a leg through one year after the end of a leg is designated as the "moratorium" period for a leg. During this moratorium, certain restrictions are applied to cores and data generated during the leg. The purpose of the moratorium is to ensure adequate time is allotted for scientific party members to conduct leg-related research before the cores and data are made available to the general scientific community.

A cored interval is designated "unique" if it has been recovered only once at a drill site. The most common occurrence of a unique interval is one that results when only one hole is drilled at a site. If the cored interval is recovered from two or more holes, then the interval is considered "nonunique."

A critical exception to this definition occurs when drilling into igneous basement rocks, metamorphic rocks, or metalliferous deposits. Every hole drilled into these lithologies is considered unique because of their inherent lateral heterogeneity.

Lithostratigraphic analysis of advanced piston cores from multiple holes drilled at one site may reveal that short sedimentary intervals (generally less than two meters) are commonly missing between successive cores from any one drill hole, even where nominal recovery approaches 100%. These missing intervals can be ignored when considering whether or not an interval is unique.

Paleoceanographic cruises typically recover sediment cores from multiple holes cored side-by-side at a given site using an advanced hydraulic piston corer (APC) and/or an extended core barrel (XCB). A composite stratigraphic depth section is constructed by establishing correlations between adjacent drill holes, using the variations in properties ("wiggles") measured on cores by nondestructive sensors. A composite depth table describes the resulting (delta) depth-offsets between holes. These offsets represent the difference between the meters below seafloor (mbsf; i.e., cored depth) and the meters composite depth (mcd; i.e., composite depth) values that are derived from these correlations. Another table describes the unique intervals in specific holes at a given site, which have been used to construct the "ideal" section, also known as the "composite splice." The purpose of a composite splice is to describe the most complete sedimentary section at a given site, without gaps in core recovery (i.e., missing sediment), which then can be used for developing high-resolution sampling strategies and analyzing time series. Scientists often prefer to sample using the composite splice as a guide, rather than to sample down a single hole at a given site, because of these gaps in recovery between cores in a single hole.

Cores are split into halves for shipboard analysis to uniquely identify split-core halves for measurements and sampling. The halves are referred to as "working half" and "archive half." The entire working half is available for sampling. The concept and definition of an archive half (see below) is designed to enhance scientific flexibility and to enable greater access to important material. In certain circumstances the archive is available for sampling (see below).

Before 1997, the archive was preserved (unsampled) and conserved in the repository, available only for nondestructive examination and analysis. Samples for destructive analyses were taken exclusively from the working half. Since 1997, the entire core has been available for sampling. The procedure of splitting cores into working and archive halves will continue, for practical and database purposes, but the concept and definition of an archive half has now been expanded and modified. This will enhance scientific flexibility by enabling greater access to important and often coveted material.

A "minimum permanent archive" is established for each ODP drill site. Archive core earmarked "permanent" is material that is initially preserved unsampled and is conserved in the core repositories for subsequent nondestructive examination and analysis. In "unique intervals," this minimum permanent archive consists of at least one half of each core, excluding whole-round samples (e.g., for interstitial pore water analysis). If so desired, the SAC may choose to designate more, but not less, than this amount as the permanent archive. In "nonunique intervals," the permanent archive will consist of at least one half of one set of cores that span the entire drilled sequence, again, excluding whole-round samples. The permanent archive is intended for science needs that may arise five years or more after drilling is completed.

In practice, if holes are cored continuously, the minimum permanent archive may consist of one half of each core taken from the deepest hole drilled at a site. As such, the archive halves of cores from additional holes drilled to equal or shallower depths, which contain replicate copies of stratigraphic intervals constituting the minimum permanent archive, need not be designated as permanent archive, but can be, if so desired by the SAC. If not deemed permanent archive, they are "temporary archive." If a composite splice section is constructed and the sampling demand exceeds the working half, an alternative scenario may be required to make sure that all samples can be taken from the spliced section. In this case, the permanent archive can be defined from cores that are not part of the splice (e.g., from cores from different holes).

Sampling of the permanent archive is feasible five years postcruise if the working and/or the temporary archive halves of the core have been depleted, according to the ODP Curator and the CAB.

Cores taken from nonunique intervals that are not part of the "minimum permanent archive" will be considered "temporary archives," unless stipulated otherwise by the SAC in the Sample Strategy. If required for special shore-based analysis, some cores may be left unsplit on board and shipped to the laboratory as whole-core sections. If split (the common scenario), the temporary archive may be sampled just like the working halves when (a) either the working halves have been depleted by sampling, or (b) when pristine, undisturbed material is needed for special sampling needs, such as taking U-channels or slab samples.

Critical intervals are lithologic spans of such scientific interest that there is extremely high sampling demand for them. These intervals may vary from thin, discrete horizons to thick units, extending over an entire core or more. Examples include, but are not limited to: décollements, sediment-basement contacts, igneous contacts, impact/tektite horizons, gas hydrates, marker ash horizons, scaly fabric, magnetic reversals, and particular biostratigraphic levels. The SAC is responsible for anticipating the recovery of critical intervals and for developing a strategy for sampling and/or conserving them. For postmoratorium sampling, the ODP Curator will work with investigators to ensure that previously defined critical intervals are sampled only when necessary.

Requests to perform nondestructive analyses on cores (e.g., descriptions, imaging, X-rays) should be submitted to the ODP Curator after completing the ODP Sample Request Form. Investigators who carry out nondestructive analyses incur the same obligations as those scientists who request samples (see Section 4 and Section 5).