Gamma-ray attenuation (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 1093. 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 "Explanatory Notes" chapter). 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 T15 and Figure F22 summarize the physical properties measurements performed at Site 1093.
At Site 1093, as with Sites 1091 and 1092, downhole variations in physical properties are controlled largely by changes in the proportion of carbonate vs. siliceous sedimentary components. Intervals rich in carbonate show (1) high GRA bulk densities that are verified by discrete-sample (moisture and density [MAD] method) bulk densities (Fig. F23); (2) lower porosity (MAD method) and higher resistivity (OSU-SCAT) values; and (3) bright reflectance with little divergence between the blue, red, or near-infrared reflectance bands. In contrast, intervals that are rich in diatoms exhibit lower density, higher porosity, and a greater contrast between blue and red reflectance. Exceptions to the above generalization occur where terrigenous grains are a significant component of the sediment.
There are four major carbonate layers within the upper 140 mcd of Site 1093 that have a similar reflectance character (magnitude and red/blue values) and correlate with similar carbonate layers in the upper 60 mcd of Site 1091 (Fig. F24). These layers are also marked by high GRA bulk density intervals (Fig. F25). The preliminary shipboard age model (see "Chronostratigraphy" sections, this chapter and "Site 1091" chapter) indicates that these layers may represent the major interglacials of the late Pleistocene (MISs 5, 7, 9, and 11). At Site 1093, red/blue values, which appear to reflect the relative proportion of carbonate vs. silica, are slightly higher (lower carbonate content) than at Site 1091, probably because of lower production or preservation of carbonate at Site 1093. In ~10-m-thick intervals that occur immediately below each carbonate layer, the magnetic susceptibility signal shows high-frequency (period <1 m) oscillations (Fig. F25). One of these layers is present between 10 and 20 mcd. These layers appear to contain more mud, sand, and dropstones (see "Lithostratigraphy"), suggesting that intervals of greater ice rafting preceded the deposition of each carbonate layer.
In the upper 290 mcd of Site 1093, there are several maxima in the red/blue values (e.g., the two intervals between 110 and 120 mcd in Fig. F24) as a result of sediments that reflect strongly in the red (650-750 nm) band. These "red" sediments may result from the diatom Fragilariopsis kerguelensis, which dominates in some intervals (e.g., ~100-125, 164, and 174 mcd; see "Chronostratigraphy"), giving the sediment an orange-tan color (Fig. F25).
In the upper 280 mcd of Site 1093, GRA bulk density and resistivity show an overall increase downhole, but a similar trend is not apparent in reflectance (Fig. F22). Between 180 and 280 mcd, magnetic susceptibility shows a greater frequency of high susceptibility values than in the upper 180 mcd, suggesting an increase in terrigenous content (Fig. F25). Smear slides (see "Lithostratigraphy") show higher sand concentrations in this interval (particularly around 240 mcd) than at any other depths in the section.
Between 290 and 460 mcd, recovery was poor, resulting in large gaps in the record (Fig. F22). With improved recovery below 460 mcd, NGR, magnetic susceptibility, and bulk density show large amplitude fluctuations. This can be attributed to a general increase in mud concentration, alternations between laminated mud rocks and diatomites (see "Lithostratigraphy"), and large amplitude fluctuations in the concentrations of these constituents.
Figure F26 shows P-wave velocities measured with the PWS3 velocimeter and P-wave logger (PWL) at Site 1093. PWS3 velocities generally increased gradually and steadily downhole from values of 1550 m/s at the top to 1600 m/s at the bottom, reflecting the gradual increase in bulk density described above. High values around 3000 m/s were measured on clasts and mud rocks below 590 mcd (Fig. F26). The recurring problem with the PWL at previous Leg 177 sites was finally rectified (see "Explanatory Notes" chapter), resulting in much better agreement between velocity measurements obtained with the PWL and the PWS3. PWL velocities are, however, somewhat lower than PWS3 velocities by a mean difference of ~20 m/s.
A total of 142 thermal conductivity measurements gave values within a narrow range of 0.54 to 0.78 W/(m·K) (Table T16, also in ASCII format in the TABLES directory; Fig. F27B). This is consistent with the results from Site 1091, where the cores are also dominantly composed of diatom ooze. Correlation with trends in bulk density is poor because the lithologic variability is small when compared to the analytical error (Fig. F27B).
At Site 1093, eight downhole temperature measurements were taken using the APCT shoe (Adara tool), one in bottom water and seven in sediment between 37 and 151 mbsf. Two additional measurements were taken in stiffer formations (251 and 482 mbsf), using the Davis-Villinger temperature probe (DVTP). Measurements were slightly to severely affected by frictional heat noise and/or cold-water flux (presumably pumped inadvertently from uphole down the drill pipe) during deployment at all stations (Fig. F28). The temperature-time series was evaluated using shipboard processing programs to derive equilibrium temperatures. Relatively large errors, estimated from repeated model curve fitting over different intervals, range from ±0.5º to ±1.0ºC (Fig. F28).
Despite the compromised data quality, the depth-temperature relationship reveals an apparently consistent temperature gradient of 93º± 3ºC/km (Fig. F29). A second-order polynomial fit yields a better correlation coefficient than the linear fit, and is more compatible with the bottom-water temperature and the deepest measurement, both of which are considered to have relatively small errors. Using an average thermal conductivity of 0.7 W/(m·K) for the sedimentary section, a moderately high average heat flow of 65 ± 4 mW/m2 is calculated for the drilled interval.