SAMPLING STRATEGY AND SAMPLING PLAN
General
Sampling of the recovered cores will be subject to the rules
described in the ODP Sample Distribution Policy (http://www-odp.tamu.edu/curation/sdp.htm). Based on the
sample requests received by 15 November 1998, the Sample
Allocation Committee (SAC) will prepare a temporary sampling
plan, to be revised on the ship according to actual coring
results. In the final shipboard sampling plan, sample requests
will be closely linked to proposed postcruise research.
Postcruise studies can also be proposed by shore-based
investigators who do not participate in the cruise.
Logistics
The core sampling logistics are three-fold: (1) shipboard
sampling for shipboard measurements, (2) shipboard sampling for
postcruise studies, and (3) postcruise sampling for postcruise
studies. Some sampling for shipboard measurement of ephemeral
properties must occur immediately, before stratigraphic
correlation information is available (see below). These
measurements include organic geochemistry for safety monitoring
(free gas and 20 cm3 sediment samples), interstitial water
chemistry (whole-round of 5-15 cm length), and moisture content
(10 cm3 sediment). In addition, core catchers will be analyzed
for biostratigraphic datums.
Shipboard sampling for postcruise studies will be kept to a
reasonable minimum, trying to balance the need for an initial set
of samples for immediate postcruise laboratory work against the
need for avoiding redundant or "frenzy" sampling before
the composite section and splice are constructed (see below). The
SAC may decide to sample the upper few cores on the ship because
high porosity sediments could be disturbed during transport to
the Texas A&M University (TAMU) core repository. Samples that
need to be frozen or sealed for shore-based analysis also must be
taken onboard. All shipboard scientists will participate in
shipboard sampling according to a shift schedule.
Because of the large number of requested samples that are
expected, most investigators will be encouraged to participate in
a postcruise sampling meeting in the core repository ~4 months
postcruise. The ODP repository staff will fill the remaining
requests.
Core
Material
Most of the material to be recovered is expected to be
hemipelagic mud with moderate carbonate content and low abundance
of organic material. Sedimentation rates are expected to range
typically between 2-20 cm/k.y., although some sites may have
substantially higher rates.
Stratigraphic
Coverage, MCD, and the Splice
Complete stratigraphic coverage will be attempted at all
sites. Because coring gaps occur, even between successive cores
with nominally 100% recovery, complete sections will be achieved
by triple coring with the APC system (typically the uppermost
150-250 m). Double XCB coring of the deeper intervals may be
considered, depending on the priority of the section and the
available time. In addition to ensuring complete coverage,
multiple-hole coring also provides significantly more core
material for sampling.
The shipboard stratigraphic correlators will be responsible for constructing a composite depth section for each site in near-real time. The "meters composite depth" (mcd) scale correlates the cores from multiple holes based on core logging data. All investigations from any hole can then be linked by using the mcd scale. A shipboard "splice" will be defined by the correlators, which is one continuous stratigraphic core section for a site composed of core intervals from different holes. The splice can be used by most investigators for sampling. However, because of the short distance from the final site to port, the "mcd splice" for the last few sites may not be available for sampling until the postcruise sampling party.
Special
Circumstances
At any time during the cruise, the SAC will determine whether
special circumstances for a certain interval warrant either a
sampling moratorium or solicitation of a special sampling
program.