Measurements of physical properties at Site 1129 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 T9, also in ASCII format), gamma-ray attenuation (GRA) bulk density (every 4 cm; Table T10, also in ASCII format), magnetic susceptibility (MS) (every 8 cm; Table T11, also in ASCII format), and natural gamma radiation (NGR) (every 16 cm; Table T12, also in ASCII format) using the multisensor track (MST). The P-wave velocity was activated only on APC cores. Thermal conductivity was measured in unconsolidated sediment at a frequency of one determination per core (Table T13, also in ASCII format), with two additional samples analyzed after deployments of the Adara temperature tool and Davis-Villinger temperature probe (DVTP) (Table T14, also in ASCII format). For this site, thermal conductivity measurements were also made on lithified sediments using the half-space needle-probe method on split cores (see "Thermal Conductivity" in "Physical Properties" in the "Explanatory Notes" chapter). Four in situ measurements of formation temperature were made (Table T15, also in ASCII format). A minimum of two discrete P-wave velocity measurements per section were made on the working half of the split cores (Table T15), and measurement frequency was increased to five per section after the P-wave velocity was turned off. Standard index properties (Table T16, also in ASCII format) and undrained shear strength (only in unconsolidated and semilithified sediments) were measured at a frequency of one per section (Table T17, also in ASCII format).
The following sections describe the quality of the data obtained, downhole variations in sediment physical properties, and their relationships to lithology and downhole logging data (see "Lithostratigraphy" and "Downhole Measurements"). Variations in MS data are described within "Paleomagnetism".
The MST provided high-quality NGR and GRA bulk density data, although problems occurred with P-wave velocity and MS measurements (see "Paleomagnetism" in the "Site 1132" chapter). Discrete P-wave velocity measurements were affected by the presence of voids between core and liner because of the high gas content of the recovered sediment. Magnetic susceptibility measurements were hindered by a low signal:noise ratio. Affected data were omitted from figures in this report but are included in the raw data tables. Difficulties also 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).
Physical properties measurements at Site 1129 correlate well with lithologic changes observed in the sedimentary section and provide an important data set for core-log correlation. Values of NGR from both whole-core and downhole logging measurements show an excellent correlation that supports the integrity of both data sets. Moisture-and-density and GRA data have similar patterns to the downhole logging data, although values are generally lower. This difference likely results from the fact that in situ density includes the influence of sediment overburden and hydrostatic pressure, whereas the laboratory measurements do not. In general, Site 1129 is characterized by significant variations in P-wave velocity, NGR, and bulk density. Variations are much less marked in porosity and MS (Fig. F24). A well-defined cyclicity is seen in the NGR record (Fig. F24) that can be correlated to downhole gamma-ray data and NGR records of Sites 1127 and 1131. Three physical properties units (PP units) can be recognized at Site 1129 on the basis of trends in measured parameters (Fig. F24).
Physical properties Unit 1 (0-40 mbsf) is characterized by an increase in NGR (from 0 to 20 cps), as seen at many other Leg 182 sites (Fig. F24). The base of PP Unit 1 coincides with the top of three bryozoan mound sequences, which form the lower part of lithostratigraphic Unit I (see "Lithostratigraphy"). Bulk density and P-wave velocity also increase toward the base of the unit (from 1.57 to 1.66 km/s and from 1.27 to 1.62 g/cm3, respectively), whereas porosity decreases from ~60% to 50% (Fig. F24).
Physical properties Unit 2 (40-270 mbsf) is characterized by high NGR values (12-52 cps) with cyclic variations. These cyclic variations correlate with coarsening-upward bryozoan floatstone-rudstone sequences (Fig. F24; see "Lithostratigraphy"). Within Unit 2, a significant P-wave velocity peak can be seen at 90 mbsf (2.02 km/s) that may correlate with a strong seismic reflector designated as Horizon 2A (see "Seismic Stratigraphy" in the "Site 1127" chapter). Between 123 mbsf and the base of Unit 2, discrete P-wave velocity data are relatively variable (Fig. F24), corresponding to alternations between unlithified and partially lithified sediments. This variability is also seen in the shear strength data (see below) (Fig. F25). A peak in P-wave velocity (2.5 km/s; Fig. F24) can be seen near 150 m, which correlates with the boundary between lithostratigraphic Units I and II (see "Lithostratigraphy") and also with the disappearance of HMC (see "Inorganic Geochemistry"). Within PP Unit 2, bulk density has low variability averaging 1.5 g/cm3 for moisture and density (MAD) and 1.7 for GRA data (Fig. F24). Some density excursions are seen that correlate with more indurated sediments (Fig. F24). Porosity decreases throughout PP Unit 2 from ~58% to 40% at the base of the unit.
Physical properties Unit 3 (270-604 mbsf) is defined by lower and generally decreasing NGR (18-12 cps) with increasing depth (Fig. F24). In contrast, P-wave velocity (1.8-2.5 km/s) and MAD bulk density (1.6-2.0 g/cm3) within Unit 3 increase with a significant shift to higher values near 390 m (Fig. F24). This change does not correlate with any noted lithologic change (see "Lithostratigraphy") but does roughly correlate with seismic Horizon 2C (see "Seismic Stratigraphy" in the "Site 1127" chapter). Porosity decreases (42%-34%) throughout Unit 3.
Undrained peak and residual shear strength were measured on unconsolidated sediments from 0 to 227 mbsf (Fig. F25). Shear strength at Site 1129 shows an overall downhole increase (2-30 kPa), resulting from sediment compaction, with high variability below 50 mbsf resulting from alternations between partially lithified to lithified sediment (Fig. F25). In some intervals, variability may also result from drilling disturbance or cracking of the sediment before sediment failure, resulting in lower values for peak strength.
Thermal conductivity values at Site 1129 range from 0.71 to 1.75 W/(m·K) (Fig. F26; Table T13). From the seafloor to 440 mbsf, thermal conductivity data define a regular increase with depth that correlates well with variations in bulk density (Fig. F26). Below 440 mbsf, thermal conductivity values increase and become more variable.
Four in situ temperature measurements were made at Site 1129, three using the Adara tool and one using the DVTP. There was relatively little variation in estimates of mudline temperature (16.24-16.97°C; average = 16.51° ± 0.22°C) (Fig. F27). Two additional estimates of seafloor temperatures (13.56° and 13.15°C) were obtained from Holes 1129B and 1129C using an expendable bathythermograph. Both yielded values lower than those obtained from the in situ temperature tools, possibly as a result of calibration differences. None of the in situ temperature measurements was affected by postemplacement movement of the probe, and differences between early and late data fits resulted in only minor differences in temperature (Table T14).
The in situ measurements define a linear temperature relationship with an intercept of 15.02° (r2 = 0.99, N = 6) (Fig. F27). This intercept is significantly less than the average mudline temperature, suggesting that there may be circulation of seawater within the upper 30-40 mbsf (cf. evidence for a 40.3-m-thick fluid advection zone noted in geochemical data; see "Inorganic Geochemistry"). However, this interpretation depends on the higher estimates of seafloor temperature from mudline readings being correct. The geothermal gradient derived from the regression equation is 41.4° ± 0.9°C/km (all uncertainties are 1 standard deviation). The geometric mean of the thermal conductivity data between 0 and 188 mbsf (1.0 ± 0.086 W/[m·K]) and the geothermal gradient determined above were used to estimate heat flow at the site. The resultant value of 41.4 mW/m2 is very similar to that determined at other sites at a similar depth on the shelf margin, although it is less than the value determined in much deeper water off the platform margin at Site 1128.