Measurements of physical properties at Site 1130 followed the procedures outlined in "Physical Properties" in the "Explanatory Notes" chapter. These included nondestructive measurements of P-wave velocity (PWL) (every 4 cm; Table T10, also in ASCII format), GRA bulk density (every 4 cm; Table T11, also in ASCII format), magnetic susceptibility (MS) (every 8 cm; Table T12, also in ASCII format), and NGR (every 16 cm; Table T13, also in ASCII format) using the MST. The PWL was activated only on APC cores. Thermal conductivity was measured in unconsolidated sediment at a frequency of one per core (Table T14, also in ASCII format), increasing to three samples per core after deployment of the Adara and DVTP tools. A minimum of two discrete P-wave velocity measurements (PWS) per section were made on the working half of the split cores (Table T15, also in ASCII format). Measurement frequency was increased to five per section after the PWL was turned off. Standard index properties (Table T16, also in ASCII format) and undrained shear strength were measured at a frequency of one per section in unconsolidated sediments (Table T17, also in ASCII format). Difficulties occurred with the pycnometer used for determination of dry volume. For index properties measurements, see "Index Properties" in "Physical Properties" in the "Explanatory Notes" chapter.
The following sections describe the downhole variations in sediment physical properties and their relationships to lithology and downhole logging measurements. Variations in MS are described within "Paleomagnetism".
Sediment physical properties data at Site 1130 reflect the homogeneous nature of the recovered sediments. In contrast to Sites 1129 and 1131, Site 1130 has relatively low concentrations of methane and H2S, and PWL velocities were the only data set that showed interference caused by sediment degassing. The small voids and airspaces resulting from degassing caused interference in transmission of the sonic signal and unacceptable variability in the data set.
Physical properties data can be divided into three units on the basis of trends in the measured parameters. Physical properties Unit 1 (0-43 mbsf) is characterized by increasing NGR values with a sharp increase at the lower boundary of Unit 1. Porosity decreases sharply throughout the unit (55% to 30%; Fig. F20). Physical properties Unit 1 correlates well with increasing pore-water salinity, potassium, and strontium concentrations, indicating active sediment diagenesis (see "Inorganic Geochemistry"). P-wave velocity increases within PP Unit 1 from 1.5 to 1.7 km/s. An offset to higher values is seen between the PWS3 data because of compression-induced increases in P-wave velocity during analysis with the PWS3 probe (see "Sonic Velocity" in "Physical Properties" the "Explanatory Notes" chapter). Bulk density shows a steady increase within PP Unit 1 from 1.5 to 1.6 g/cm3 (Fig. F20).
Velocities of P-wave within PP Unit 2 (43-254 mbsf) remain constant near 1.75 km/s (Fig. F20). Bulk density increases slightly throughout the unit from 1.7 to 2 g/cm3, whereas porosity remains relatively constant (32%-37%) (Fig. F20). The increases in P-wave velocity and bulk density are likely to be a response to lithostatic compaction. The most intriguing result from PP Unit 2 is the cyclic variability in NGR data (Fig. F20). These variations are well correlated to changes in color reflectance and are likely to be driven by changes in the carbonate/terrigenous sediment ratio. The lower boundary of PP Unit 2 (254 mbsf; Fig. F20) is characterized by a marked drop in NGR (20-<10 cps). This boundary correlates with the lower boundary of lithostratigraphic Unit I, corresponding to a sediment change from packstone to nannofossil ooze (see "Lithostratigraphy").
Physical properties Unit 3 (254-330 mbsf) is characterized by low NGR (<10 cps), an increase in porosity (~30%-40%), and bulk density values between 1.4 and 1.75 km/s (Fig. F20). P-wave velocity data show no change from PP Unit 2 to PP Unit 3. Poor recovery precludes recognition of further PP units below 330 mbsf.
The trends in NGR values from both whole-core and downhole logging measurements are well correlated, although downhole values are greater (Fig. F21). This supports the integrity of both data sets. Moisture and density and GRA data are consistently lower than downhole logging density data (Fig. F21). This difference results from the fact that in situ density includes the influence of sediment overburden and hydrostatic pressure, whereas the laboratory measurements do not. A similar effect is seen in the P-wave velocities, particularly deeper than 140 mbsf, where in situ velocities are higher than those measured on discrete samples. Log data confirm the location of the boundary at 254 mbsf, as similar shifts are seen in both data sets (Fig. F21).
Undrained peak and residual shear strength were measured on unconsolidated sediments from 0 to 180 mbsf (Fig. F22; Table T17). Shear strength at Site 1130 increases linearly with depth (0-40 kPa), with peaks in the data corresponding to more indurated portions of the sedimentary section. Shear-strength variability increases downhole. In part, this is a result of differences in lithification, but it may also result from drilling disturbance or cracking of the sediment before failure.
Thermal conductivity values from Site 1130 range from 0.8 to 1.38 W/(m·K) (Fig. F23; Table T14). In general, thermal conductivity data increase with depth (0-254 mbsf) and correlate best with bulk density and discrete P-wave velocity (Fig. F23). The increase in thermal conductivity is primarily caused by lithostatic compaction and the resulting increase in bulk density. Thermal conductivity decreases below 270 mbsf (1.4-1.0 W/[m·K]) because of a lithologic change below the PP Unit 2/Unit 3 boundary.
Four in situ temperature measurements were made at Site 1130: three using the Adara tool and one using the DVTP (Fig. F24). A good linear fit can be obtained (r2 = 0.95, N = 10) if the lower estimates of mudline temperature are used. The geothermal gradient derived from this regression is 35° ± 3° C/km. As a result of the increase in thermal conductivity with depth, the geometric mean of the interval 0-150 mbsf was used for the determination of heat flow (0.968 ± 0.069 W/[m·K]). Using this value and the geothermal gradient determined above, heat flow is estimated at 33.9 mW/m2.