PHYSICAL PROPERTIES

GRA bulk density, magnetic susceptibility, natural gamma-ray (NGR) emission, and P-wave velocity were measured with the MST on most whole-core sections recovered from Site 1088 (Table T13). Color reflectance and resistivity were measured on the working half of all split APC cores using the Oregon State University Split Core Analysis Track (OSU-SCAT) (see "Lithostratigraphy" in the "Explanatory Notes" chapter). Other physical properties measurements conducted on discrete 10-cm³ samples in-cluded moisture, density, and P-wave velocity (Table T13). Samples for moisture and density determination were taken at an average of two per section. Measured parameters were initial wet bulk mass (M_b), dry mass (M_d), and dry volume (V_d). Velocity was measured on split-core sections using the P-wave velocity sensor 3 (PWS3). Comparisons between the whole-core MST data and physical properties measured on discrete samples are shown in Figure F20.

Multisensor Track

P-wave velocity, GRA bulk density, magnetic susceptibility, and NGR were determined every 2 cm for all cores from each hole. Sampling time was 4 s at every point for each sensor. Data were reduced with a 10-point running average for presentation in this report (Fig. F20). P-wave velocities were not measured for the XCB cores from Hole 1088C. Magnetic susceptibility shows characteristic downhole fluctuations, although the intensity was very low with only small variations. NGR values generally correspond to the variations of magnetic susceptibility (Fig. F20).

P-wave Velocity

Velocity data gathered by the MST P-wave logger (PWL) were of poor quality. This was partly the result of coarse-grained foraminifer ooze in the upper part of the holes that resulted in high signal attenuation. In cores from the lower parts of the holes, there was insufficient contact between the sediment and the core liner, resulting in poor signal transmission. This can cause, for example, the second rather than first wavelet to be auto-picked by the PWL, which may result in the bimodal velocity distribution (80 m/s difference) seen in Figure F20. Average velocities were around 1500 m/s. P-wave velocities measured with the PWS3 velocimeter were consistently greater than those logged by the PWL. Shallow cores had average velocities around 1700 m/s. Scatter in the data increases downhole because of anomalously high velocities (~1900 m/s) in the center of some core sections. The density data show a smooth increase downhole (Fig. F20). In both the PWL and PWS3 data sets the overall trend in velocity was a decrease downhole.

Moisture and Density

Moisture content and density were determined on two samples per core section in Hole 1088B and in the APC cores from Hole 1088C. The results are shown in Figure F20. The overall trend of the wet bulk density profile is a downhole increase caused by compaction. There is good agreement in this trend with GRA densities, although GRA densities are consistently ~0.05 g/cm³ greater (Fig. F21). Grain density increased gradually downhole, coincident with increasing carbonate concentrations (Fig. F22).

Resistivity and Porosity

Resistivity measurements at Site 1088 show greatest values at the top of the cored interval and gradually decrease downhole. Resistivity values range from 0.35 to ~0.8 m, with discrete spikes exceeding 1.0 m. In general, resistivity is inversely proportional to sediment interstitial water content for a given lithology and is, therefore, expected to increase with depth as porosity decreases because of compaction. The resistivity profile at Site 1088 is atypical in that resistivity actually decreases downhole, whereas porosity measured on discrete samples decreases (Fig. F20). This may be an artifact resulting from failure of the thermistors on the landing board of the OSU-SCAT, giving unreliable core temperatures. Figure F20 was produced using an assumed core temperature of 20°C. Calibrated thermistors were installed for later sites and this atypical relationship between resistivity and porosity was not observed at Site 1089. An alternative explanation could be the decreasing grain size of the terrigenous and carbonate fraction with depth (see "Lithostratigraphy") at Site 1088. Greater total grain surface area with ionic clouds around the grains may lead to greater "surface" conductivity than normal interstitial water.

Diffuse Spectral Reflectance

Diffuse spectral reflectance variations in four 100-nm bands correlate well with each other at Site 1088, and the overall trend is a downward increase (Figs. F23, F24). A long-term trend toward higher reflectance that begins at the top of Hole 1088B and continues through ~60 mbsf is apparent in each of the 100-nm color bands. Values in the red band range from lows of ~30% to highs of ~70%. Superimposed on the long-term trend is cyclic behavior with a depth scale of ~1 m. At depths below ~60 mbsf, reflectance exhibits relatively constant mean values. This pattern is also observed in the GRA density measurements (Fig. F24) and the carbonate measurements from Site 1088 (see "Geochemistry"). The positive correlation between high reflectivity and high density, and low reflectivity and low density sediments, suggests that color and density variations at Site 1088 are largely driven by variations in sediment carbonate content.

Heat Flow

A total of 23 thermal conductivity measurements conducted on core sections gave values ranging from 0.83 to 1.21 W/(m·K) (Fig. F25; Table T14, also in ASCII format in the TABLES directory).

Five downhole temperature measurement attempts were made at Site 1088: one in bottom water about 20 m above the seafloor, and four in sediment with Cores 177-1088-4H, 7H, 11H, and 14H (Table T15). Four measurements yielded very noisy data which could not be used to estimate the temperature (Fig. F26). This is probably the result of considerable ship heave, which created random frictional heat. One attempt had an electronic failure and did not collect any data. A meaningful determination of the heat flow was therefore impossible at Site 1088.