Shipboard physical properties measurements included determination of compressional (P-wave) ultrasonic velocity, wet bulk density, magnetic susceptibility, and natural gamma radiation with the MST system on whole-round sections of cores from each hole (see "Explanatory Notes" chapter, this volume).
Index properties (gravimetric wet bulk density, porosity, and moisture content) were measured on one or two samples (volume = ~10 cm3) per working-half section on all cores from Hole 1081A. Method C was used at this site (see "Explanatory Notes" chapter, this volume).
Discrete ultrasonic compressional (P-wave) velocity and undrained vane shear strength measurements were made at a resolution of about one or two sample points per section. For the discrete P-wave measurements, the modified Hamilton Frame was used to make ultrasonic measurements through the core liner.
Thermal conductivity was measured in every second section of each core at Hole 1081A.
GRAPE density (Fig. 42), P-wave velocities (Fig. 43), and magnetic susceptibility (Fig. 44A) were determined every 4 cm, and natural gamma radiation was measured with a sampling period of 30 s at 32-cm resolution (Fig. 44B). MST data are included on CD-ROM (back pocket, this volume). Compressional velocities were recorded at a threshold of 100 incremental units to automatically exclude weaker signals from the profile. Deepest measurements with the MST P-wave logger were recorded at 80 mbsf, even before the discrete velocity measurements were terminated (Fig. 43). MST veloc-ity and discrete velocities are not well correlated. An explanation cannot be given at this stage. At 70 mbsf, the MST profile merges with the discrete velocity profile.
Profiles of magnetic susceptibility and natural gamma radiation show a positive correlation throughout the entire depth range (Fig. 44A and Fig. 44B, respectively). GRAPE density values generally agree with the discrete wet bulk density data (Fig. 42), though GRAPE values are higher between 0 and 80 mbsf and lower or equal below 80 mbsf. Density core logs show a significant variability and a pronounced cyclicity in some intervals. Density anomalies (e.g., at 78 and 100 mbsf) coincide in many intervals with features observed in the logging and lithostratigraphic analysis (see "Downhole Logging" and "Lithostratigraphy" sections, this chapter). Natural gamma radiation shows a pronounced maximum at 240 mbsf. These features seem to correspond to dolomite horizons.
Discrete velocities range between 1535 and 1590 m/s, whereas P-wave logging with the MST shows lower values (Fig. 43). At 80 mbsf, a gradual increase of 50 m/s is observed over a depth range of 10 m. Below 25 mbsf, discrete velocity and the GRAPE density profiles correlate well.
Results of discrete measurements of wet bulk density, porosity, and moisture content are presented in Figure 45A, Figure 45B, and Figure 45C, respectively (also see Table 14 on CD-ROM, back pocket, this volume). The density values vary between 1250 and 2200 kg/m3. Very sharp peaks are noticed at 122 and 220 mbsf.
Porosities decrease from 82% in the top section to 55% at 300 mbsf (Fig. 45B), and moisture content varies between 68% at the top of Hole 1081A and 30% at 300 mbsf (Fig. 45C).
The thermal conductivity profile at Hole 1081A was measured in every second core section (see "Explanatory Notes" chapter, this volume). The profile shows a high degree of similarity with the magnetic susceptibility and natural gamma radiation profile (Fig. 44C), indicating major compositional changes.
In Hole 1081A, the Adara tool was deployed to measure formation temperature. A preliminary analysis provided four data points, which were used to estimate a geothermal gradient of 51°C/km, but further analyses will be required to confirm this result.
An undrained vane-shear measurement was performed in the bottom part of each core section. The profile shows a gradual increase in vane shear from the top of Hole 1081A to 120 mbsf (Fig. 44D). As at previous sites, higher values of shear strength were found primarily in the middle sections of each core, as can be seen from the position of the indicated core breaks. Scatter increases below 70 mbsf. The change from APC to XCB drilling is apparent below 160 mbsf by a decrease of vane shear strength. Data quality below 155 mbsf is significantly affected by drilling disturbances and coring.