This leg offers an opportunity to reconstruct continuous records of Southern Ocean paleoclimate variability using core and log data. Sediments encountered at these sites will consist of periodically alternating layers of biosiliceous and carbonate sediments, with variable amounts of fine (clays) and coarse (ice-rafted debris) terrigenous clastics. Because of the strong density and porosity variations associated with this lithologic variability, core and log physical property indices will very likely be extremely valuable proxy measurements for reconstructing sediment composition time series. Some sites have very high sedimentation rates, so there is great potential for generating very high resolution records of regional paleoclimatic and paleoceanographic variability. Previous ODP logging in the region (e.g., Site 704) indicate that strong physical property variability related to the paleoclimatic opal-carbonate-terrigenous bedding cycles will be observed.

Downhole logging is scheduled for all holes deeper than 400 m, which currently includes Sites TSO-2B and TSO-6A. At these sites, the Triple Combo, Formation MicroScanner (FMS), and Geological High-resolution Magnetometer (GHMT) will be deployed to develop continuous high resolution paleoclimate records and augment the results of coring. The Triple Combo tool string provides measurements of spectral gamma ray, porosity, density, and electrical resistivity. 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, hiatuses, and cyclicity recorded by sediments. A sonic tool will be run with the FMS to provide acoustic data useful in establishing synthetic seismograms and seismic line calibration. The GHMT provides both continuous in situ magnetic susceptibility and the vertical component of the total magnetic field data. If the remnant magnetization of the sediments is sufficiently stong, the total field measurement of the GHMT can provide magnetic reversal stratigraphy.

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