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doi:10.2204/iodp.sp.319.2009

Sampling and sample coordination

Expedition 319, for the first time in ODP or IODP, will be sampling cuttings from riser drilling as well as a limited number of sediment cores. As a result, sampling and sample coordination will involve a new combination of shipboard analysis, sample collection, and sample archiving that, although outlined in the follow paragraphs, will probably evolve as samples are processed during the expedition. Sampling of retrieved cores will follow traditional IODP policy, including discrete samples, whole-round samples (both individual requests and "community whole rounds"), and sample clusters (see additional explanation of community whole rounds and sample clusters in "Sampling sediment cores"). In contrast, sampling cuttings from riser drilling will follow a preliminary set of guidelines developed, in part, from experience transferred from the oil industry and from the SAFOD drilling program. The core and cuttings sampling strategy was developed by the NT-PMT in consultation with the Sample Allocation Committee (SAC) (see "Sample requests and coordination") to best meet the drilling project's objectives and the needs of the science party. A short review of core sampling and archiving is provided below followed by a more detailed discussion of sampling and archiving of cuttings. Shipboard and shore-based researchers should also refer to the IODP Sample, Data, and Obligations Policy (www.iodp.org/program-policies).

Sampling sediment cores

Cores are typically split into a "working half" and "archive half" with the working half being available for sampling by shipboard and shore-based scientists. Although the archive half is also available for sampling in certain circumstances, it is primarily designed to preserve retrieved material while providing flexibility and broader access to important material postcruise. Samples of whole-round cores can also be requested following IODP policy.

The unique, multiexpedition nature of NanTroSEIZE has also required the modification of normal IODP sampling policy and routines in sampling sediment cores. Specifically, these include: (1) community whole-round cores that are archived (at the Kochi Core Repository) for postcruise distribution and (2) sample clusters taken as a suite of basic scientific measurements collected onboard from a much smaller (1–2 cm thick) whole-round core. These basic measurements consist of pore water, carbonate, moisture and density, and bulk X-ray diffraction (XRD). Community whole-round cores and sample clusters are typically collected from each section.

Community whole-round core samples

As usual, individual scientists will collect whole-round samples for shipboard analyses and their postcruise research. In addition, however, we intend to collect "community" archive whole-round samples, which will augment and/or provide redundancy for those requested by shipboard scientists. The goal is to preserve samples for a wide range of overall science objectives after the expedition and over the duration of the NanTroSEIZE project. Community whole-round cores are typically collected from each core.

Sample clusters

To ensure achievement of overall NanTroSEIZE scientific objectives and maximize the ability to correlate different shipboard data sets, it will be essential to co-locate suites of essential data types (pore water, calcium carbonate, moisture and density, bulk XRD, and bulk chemistry). This will be done with appropriate and consistent sample spacing throughout each site's stratigraphic succession. Sample clusters are normally collected from each section.

Sampling and archiving drill cuttings

Unwashed drill cuttings are delivered continuously to the shale shaker where they are sampled by the "Sample Catcher" at a frequency equivalent to every 5 m of drilling penetration (Fig. F14A). The Sample Catcher then splits the cuttings into two splits–one for the Mud Logger and the second for the IODP scientific analysis. The IODP cuttings sample has a volume of ~1.5 L, depending on the volume of total sample requests, and is transferred to the Laboratory Roof Deck (by a MQJ "Roustabout"), where it is again split into two portions: a 400 cm³ portion for archiving (the "archive portion") and a 1000 cm³ portion for analysis and sampling (the "working portion") (Fig. F14A, F14B). The working portion is available for scientific sampling and analysis at any stage of the cleaning, sieving, and preliminary analysis shown in Figure F14B (potential sampling intervals are noted with diamonds). A portion of the archived cuttings (designated as a "temporary archive") is also available for sampling and analysis after the moratorium and approval of the SAC. Shipboard analysis of the working portion normally includes:

• gamma ray,

• moisture and density,

• lithologic descriptions (through smear slides and thin sections),

• XRD and X-ray fluorescence analyses,

• magnetic susceptibility,

• total carbonate (using carbonate analyzer), and

• total carbon and nitrogen (using CHNS/O elemental analyzer).

Sample requests and coordination

Because NanTroSEIZE is a long-term multiexpedition drilling project that includes several linked expeditions over several years that share overarching scientific objectives, sampling and coordination of individual samples and data requests are somewhat different than for single expeditions. These differences include the recognition of Specialty Coordinators, unique data sharing opportunities, and a more integrated sample and data request program. Key aspects of these differences are described below.

Specialty coordinators

Unlike traditional stand-alone ODP/IODP legs and expeditions, unusual amounts of coordination and collaboration must occur among science parties across expeditions and within the framework of overall NanTroSEIZE goals. Specialty Coordinators, in collaboration with Co-Chief Scientists, will be responsible for facilitating collaborations between the participants on the two parts of Expedition 319, as well as identifying research or sampling gaps or collaborations in addition to those planned by shipboard science parties but needed to advance the overall NanTroSEIZE scientific goals. They will also provide technical and scientific guidance to each science party. The NT-PMT has identified six specific research areas that require special effort over the project's duration:

1. Lithology and sedimentary petrology,

2. Structural geology,

3. Geotechnical properties and hydrogeology,

4. Geochemistry,

5. Core-log-seismic integration, and

6. Paleomagnetism and biostratigraphy.
   

Data/Sample sharing

Data sharing across expeditions is normally accommodated through a formal data/sample request; that is, scientists from one expedition can apply as a shore-based scientist for shipboard data/samples from a completed or planned expedition. In this context, all Expedition 319 scientists are encouraged to submit a request for data/samples from other IODP expeditions, including Expedition 322, if they are interested in conducting postcruise research that furthers the science objectives of those expeditions. In the case of NanTroSEIZE, it is also possible that drilling or scientific objectives will overlap across two or more expeditions to such an extent that the expeditions will be considered one expedition in terms of shipboard data and samples. In these cases, data can be shared without a separate data/sample request. This may occur, for example, for scientific or logistical reasons during preexpedition planning or during the expedition, if contingency sites are drilled that overlap with a planned expedition. The decision as to whether an expedition is a stand-alone expedition in terms of data/samples or is part of a suite of expeditions is made by the NT-PMT in consultation with the SAC and the Co-Chiefs of the involved expeditions.

As a specific example, if proposed Site NT1-01A is drilled during Expedition 319 but partially or wholly analyzed during Expedition 322, the science parties of Expeditions 319 and 322 will be merged in order to best address the common theme of characterizing subduction inputs. In this scenario, scientists participating in either expedition will have full access to all samples and data from both expeditions, and sample requests will be reviewed and evaluated jointly by the two expedition SACs. This is somewhat different than most previous ODP/IODP expeditions, but will follow the precedent and procedures defined during NanTroSEIZE Stage 1 drilling (e.g., Ashi et al., 2008; Kimura et al., 2008).

Sample and data requests (research proposals)

All shipboard scientists must submit at least one data or sample request in advance of the drilling expedition. Additional requests also may be submitted during or after the expedition if appropriate. The initial sample requests provide the basis for the SAC and Specialty Coordinators to develop an integrated sampling program of both shipboard and postcruise sample requests. The initial sampling plan, of course, will be subject to modification depending upon the actual material/data recovered and on collaborations that may evolve between scientists before and during the expedition(s). Modifications to the sampling plan during the expedition require the approval of the SAC. To provide time for the SAC and Specialty Coordinators to develop a detailed and integrated sampling strategy, sample requests are due by the end of March 2009.

The IODP Sample, Data, and Obligations Policy (www.iodp.org/program-policies) outlines the policy for distributing IODP samples and data and defines the obligations incurred by both ship board and shore-based scientists. Both groups of scientists should also use the Sample/Data Request form (smcs.iodp.org) in submitting their requests.

Additional sampling guidelines

The SAC is composed of Co-Chief Scientists, Expedition Project Managers (EPM), the shipboard curatorial representative, and the IODP curator on shore; the SAC for the expedition(s) must approve access to data and core samples requested during the expedition and during the 1 y moratorium, which starts at the end of the drilling expedition. In the event that proposed Site NT1-01A is drilled during Expedition 319, the shared moratorium will then begin from the end of Expedition 322.

All sample frequencies and sizes must be justified on a scientific basis and will depend on core recovery, the full spectrum of other sample/data requests, the expedition objectives, and project-wide NanTroSEIZE objectives.

When critical or volumetrically limited intervals are recovered, there may be considerable demand for samples because of the limited amount of cored material. These intervals (e.g., highly deformed fault zone) may require special handling, a higher sampling density, reduced sample size, or continuous core sampling for a set of particular high-priority research objectives. The SAC may require an additional formal sampling plan before critical intervals are sampled.

All sampling to acquire ephemeral data types or to achieve essential sample preservation will be conducted during the expedition.

Sampling for individual scientists' postcruise research may be conducted during the expedition, or may be deferred to postcruise.

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