Ultra-high Resolution Sites
There is a possibility that varves will be encountered in some sites, notably in Walvis Basin. Detailed sampling will be necessary to achieve objectives in such sections. The sampling allocation committee ([SAC], consisting of the Co-chiefs, Staff Scientist, and Curator's representative) will determine details of the sampling pattern in these cases.
Sampling Time Table
Detailed sampling of cores from a given site will proceed after a composite stratigraphy is constructed from cores from the two or more holes drilled at the site. The splice will be constructed, and the stratigraphic information will be distributed to the scientific party in advance of post-cruise sampling to facilitate planning and scientific collaboration. Requests to sample on board, for pilot studies or for projects requiring lower stratigraphic resolution, will be considered by the SAC.
General Sampling Procedure
Investigators should avoid sampling the center of core halves. Sample plugs should be taken as close to the edges of a core half as is feasible, given the purpose of sampling. Samples may also be taken with the "scoop" tool, which inherently takes samples from the edges of the core half. Large samples taken with the "cookie-cutter" tool, for example for lamina-scale studies, should be shared among interested scientific party members.
The permanent archive will be the ODP-defined "minimum permanent archive." Once the working half of a section is depleted, the temporary archives for that section will be accessible for sampling. Wherever possible, one quarter of such temporary archives should be preserved by sampling off-center to one side.
Special Core Handling
Large numbers of samples for organic geochemistry analysis may be taken and may need to be frozen.
Only holes deeper than 250 m will be logged with a combination of geophysical sensors: Triple
combo tool, the Formation MicroScanner (FMS) associated with the sonic tools, and the
geological high-sensitivity magnetic tool (GHMT). The Triple-combo provides measurements of
gamma ray, porosity, density, and electrical resistivity, which will be used to describe the
lithology, sedimentary fabric, degree of lithification, and fluid composition. The FMS tool string
produces high-resolution electrical resistivity images of the borehole wall that can be used to study
the structure of bedding, diagenetic features, hiatus, and cyclicity recorded by sediments. The sonic
tool coupled to the FMS can be useful to establish synthetic seismograms. By combining acoustic
velocity with density evaluations and then convolving them with appropriate wavelet techniques,
we can accurately calibrate the seismic lines. The GHMT provides continuous measurements of
magnetic susceptibility and the vertical component of the total magnetic field. This latter
measurement provides a magnetic reversal stratigraphy, if the magnetization of the sediments is
To 175 References
175 Table of Contents