GRA bulk density, magnetic susceptibility, natural gamma-ray (NGR) emission, and P-wave velocity were measured with the MST on whole-core sections recovered from Site 1090 (Table T14). 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). Color reflectance was also measured with the Minolta CM-2002 spectrophotometer on cores from Hole 1090B (Table T14). Other physical properties measurements conducted on discrete core samples included moisture, density, and P-wave velocity. Measured parameters were initial wet bulk mass (Mb), dry mass (Md), and dry volume (Vd). Velocity was measured on split-core sections using the P-wave velocity sensor 3 (PWS3). Table T14 summarizes the physical properties measurements performed and their sampling frequency.
There is good agreement between discrete-sample (determined using the moisture and density [MAD] method) and GRA bulk densities (Figs. F25, F26, F27). Densities range between 1.2 and 1.8 g/cm3. The trend in bulk density at Site 1090 is mainly controlled by downhole variations in carbonate vs. biogenic opal concentrations. Highest densities are associated with carbonate oozes in the top 70 and bottom 100 m, and lowest densities occur between 250 and 320 mcd, corresponding to an interval that is particularly rich in diatom ooze. There is a sharp drop in density across a disconformity that occurs around 70 mcd, below which biogenic opal becomes a significant component of the sediment and carbonate content decreases (see "Lithostratigraphy"). GRA bulk density generally covaries with magnetic susceptibility and NGR records. The dominant period of this cyclicity is approximately 50-60 m, and superimposed on this signal is a higher frequency cyclicity with a period of ~5 m.
In the uppermost 40 mcd, resistivity, GRA bulk density, NGR emission, and reflectance show a cyclicity with a period of ~5 m (Fig. F26), which is not well represented in the magnetic susceptibility record. Reflectance and NGR show an inverse correlation, probably as a result of dilution of the more radiogenic terrigenous minerals by carbonate (i.e., low NGR emission and high reflectance). The low porosity of the carbonate results in the high resistivity and GRA bulk density observed.
There is one notable exception to the otherwise good correlation between resistivity, GRA bulk density, magnetic susceptibility, and NGR below 350 mcd, where the magnetic susceptibility record becomes particularly noisy, possibly related to large fluctuations in carbonate content or introduction of gravel contamination during the drilling process (see "Lithostratigraphy").
P-wave velocities measured with the PWS3 velocimeter were slightly greater on average than those logged by the P-wave logger (PWL) of the MST. In both records, velocities were fairly constant with depth (Fig. F25). The greater scatter in PWL data is probably an artifact of the quality of the contact between the core liner and the sediment or of a wrong threshold setting (see "Physical Properties" in the "Explanatory Notes" chapter). This may result in a lower signal level and the second rather than first wavelet being auto-picked by the PWL. This leads to longer traveltimes and lower velocities being recorded.
Porosity determined gravimetrically
on discrete samples (MAD method) ranged from 87% to 62% at Site 1090. Porosities were
actually greatest in the deeper part of the hole between 250 and 300 mcd (Fig. F25), the same interval in which bulk densities were
smallest. This reflects the greater water content of siliceous ooze as well as the lower
grain density of biogenic opal, as compared with carbonate. Resistivity shows the expected
inverse relationship with porosity, with the greater average values (0.224 
m) that are associated with high
carbonate concentration occurring within the upper 70 mcd. Resistivity decreases sharply
below this depth, with the exception of discrete spikes of ~2 m within the tephra layer at 71 mcd
(Figs. F25, F26).
Below the tephra layer, resistivity values range from 0.1 to 0.5 m, with average values around 0.2 m.
Diffuse reflectance of APC recovered sediments from Site 1090 was measured with the OSU-SCAT system at 4- to 6-cm resolution. The XCB sediments from Hole 1090B were scanned with the handheld Minolta CM-2002 spectrophotometer at a nominal resolution of 5 cm to avoid fractures and coring disturbance. For comparison with the OSU-SCAT data, averages in the blue (450-550 nm) and red (650-700 nm) bands were calculated.
Sediments from Site 1090 exhibit rhythmic variations in reflectance on depth scales ranging from decimeters to several meters (see Fig. F4). Down to the hiatus at 70 mcd, cyclic changes in sediment color are reminiscent of classic Southern Ocean carbonate stratigraphic sections such as those recovered at ODP Site 704 (Shipboard Scientific Party, 1988b). Below the hiatus, there is evidence of cyclic color variability in both the APC (see Fig. F4) and XCB (Fig. F28) sediments recovered, although postcruise analysis with firm age control will be required to elucidate the exact nature of this variability.
Comparison of OSU-SCAT blue and red reflectance to carbonate measurements (see "Geochemistry") indicates a clear relationship (Fig. F29). This pattern is similar in character to that observed in North Atlantic sediments at ODP Site 984 (Shipboard Scientific Party, 1996) and is observed for Pliocene-Pleistocene sediments from Sites 1088-1090, as well as early Miocene sediments below the hiatus at Site 1090. Interestingly, whereas red reflectance and carbonate data from Pliocene-Pleistocene sediments plot along a single trajectory, lower Miocene to middle Eocene sediments from Site 1090 are systematically redder. This increase in red reflectance is presumably caused by the downhole increase in red-clay content as indicated by visual observation and XRD analysis (see "Lithostratigraphy"). This systematic behavior can be clearly seen in a plot of blue and red reflectance vs. depth. Sediments above the hiatus exhibit a smaller red/blue contrast than those below (Fig. F30).
A total of 166 thermal conductivity measurements were made on cores from three holes at Site 1090 (Table T15, also in ASCII format in the TABLES directory; Fig. F31). The measured values range from 0.65 to 1.22 W/(m·K). The highest values (>1.15 W/[m·K]), measured from the bottom of the hole, are associated with the highest carbonate values. The lowest values measured (<0.7 W/[m·K]) correlate with distinct diatom ooze layers. Therefore, the first peak mode in the distribution of thermal conductivity values at 0.8 W/(m·K) appears to represent lithologies dominated by siliceous oozes, and the second peak mode at 1.0 W/(m·K) is associated with calcareous oozes (Fig. F31). Thermal conductivity is expected to be controlled mainly by interstitial water content and grain density, and the measurements from this site exhibit a significant linear relationship between thermal conductivity and bulk density measurements, yielding a correlation coefficient of 0.88 (Fig. F31).
