UNDERWAY GEOPHYSICS

SAMPLING STRATEGY

Sample requests may be submitted by shore-based and shipboard scientists, preferably three months before the beginning of the cruise via the electronic form (http://www-odp.tamu.edu/curation/subsfrm.htm). About two months precruise, the SAC will prepare a temporary sampling plan, which will be revised on the ship as needed. Minimizing redundancy of measurements among the science party, both shipboard and shore-based scientists, will be a factor in evaluating sample requests. The sampling plan will be subject to modification depending upon the actual material recovered and collaborations that may evolve between scientists during the leg.

Shipboard and Shore-Based Samples
We wish to emphasize that given our paleomagnetic objectives, maintaining the orientation of core pieces is critical for the success of the leg. Therefore, special labeling and sampling procedures may be developed to ensure that core handling and sampling does not compromise core piece orientations. We plan to RCB core a single hole at each site and to drill rather than core part of the sedimentary section at the Meiji Guyot and Detroit Seamount sites as indicated in Table 1. Samples for shipboard studies will be collected following core labeling, nondestructive whole-core measurements (multi-sensor track measurements and core images taken for core reorientation), core splitting, and further labeling of individual pieces of core (including orientation labeling). The shipboard samples will be collected from working halves of cores by the shipboard party.

Given the paleomagnetic objectives for the leg, we anticipate collecting a large number of oriented samples for reconnaissance shipboard paleomagnetic measurements. The paleomagnetic data from these shipboard samples will be used to assess on site whether secular variation has been averaged by the recovered lava flows. However, shipboard samples should not be taken in a way that compromises (or destroys) the orientation of the core piece. Other shipboard samples will also be collected at this time for shipboard geochemical and mineralogical analyses, for making polished thin sections, and for physical properties measurements. Similarly, these samples must be taken in a way that does not compromise the unambiguous orientation of core pieces.

Samples for shore-based studies will be collected toward the end of the cruise to devise sampling strategies that take advantage of the information obtained from the shipboard measurements. Generally, shipboard scientists may obtain up to 100 samples in volcanic units, with the size of individual samples being <15 cm³ in most cases. In special cases, additional or larger samples may be obtained with the approval of the SAC. Soon after the cores return to the ODP Gulf Coast repository, additional samples may be obtained upon written request.

Short intervals of unusual scientific interest (e.g., K/T boundary sections, veins, ores, glass, and dikes) may require careful handling, higher sampling density, reduced sample size, continuous core sampling by a single investigator, or use of sampling techniques not available on board the ship. These intervals will be identified during the core description process, and a specific sampling protocol will be established by the interested scientists and the shipboard SAC.