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Stratigraphic correlation and composite section

Physical property measurements of whole-round sections are strongly impacted by the high concentration of diatoms in the sediments as well as pervasive gas expansion and release. Therefore, density (Fig. F43) and velocity data are of very poor quality (or lacking). In addition, magnetic susceptibility is at or below the instrument noise level. Stratigraphic correlation between the three holes at Site U1357 is problematic because of the nature of the available shipboard data (Fig. F43).

Some core sections from Hole U1357A and all core sections from Holes U1357B and U1357C were run through the NGRL (see “Physical properties”). The NGR data from cores from Holes U1357A, U1357B, and U1357C from a comparable depth range (~40–70 mbsf) exhibit very low counts, on the order of 3–5 cps. Nevertheless, a possible characteristic feature (sudden step from relatively higher to relatively lower values) was recorded in all holes, which may serve as a tie point for correlation between the holes (Fig. F44).

A complete composite section may not be possible with these shipboard data and may have to be resolved with shore-based data such as color, core imaging, and X-ray fluorescence scanning.