The physical properties program at Site 1171 included MST and thermal conductivity measurements of whole-round cores and compressional wave (P-wave) velocity, moisture and density (MAD), and vane shear-strength measurements of split cores. The Adara tool was deployed once each in Holes 1171A and 1171B for in situ temperature measurements.
All core sections from Holes 1171A, 1171B, 1171C, and 1171D were routinely measured on the MST (for magnetic susceptibility, P-wave velocity, and GRA density) at 2- to 3-cm intervals. P-wave velocities were recorded only in APC cores from Holes 1171A, 1171B, and 1171C.
Variations in magnetic susceptibility (Fig. F39A) correlate with lithologic changes downcore. Magnetic susceptibility remains low through high-carbonate intervals (lithostratigraphic Units I and II), while the glauconite-rich sediments of Unit III are characterized by a sharp increase in magnetic susceptibility. Units III and IV are characterized by alternating lithified and unlithified intervals, associated with high and low values of magnetic susceptibility respectively. Magnetic susceptibility increases through Subunit VC and remains high through Unit VI.
Density generally increases between the seafloor and 950 mbsf as a result of normal sediment compaction and dewatering trends (Fig. F39B). Although the first-order GRA and discrete density trends are similar, GRA-density and discrete density values show some downcore offset. GRA values are higher than discrete values in carbonate-rich sections (between ~40 and 270 mbsf). Because the MST is optimized for mixed sediments, the calibration procedure overestimates densities in carbonate-rich sediments. MAD measurements are higher than recorded GRA-density values from Hole 1171D (390 mbsf to total depth [TD]). The RCB cores in Hole 1171D did not fill the core liner; therefore, this difference in measured density is expected because GRA processing assumes the core diameter equals the liner diameter.
At ~520 mbsf, there is a large positive shift in GRA and discrete density that corresponds to an increase in P-wave velocities (Fig. F32 in the "Site 1172" chapter) and magnetic susceptibility, but does not appear to correspond to a compositional change. These changes in core physical properties correspond to variations seen in the downhole density, Th, and U logs (see "Downhole Measurements"), and dinocyst biostratigraphy (see "Biostratigraphy"), which all suggest a hiatus is present. At this same interval, low-TOC and high-HI values are observed (see "Organic Geochemistry"), suggesting the interval is a condensed section.
Compressional velocities were obtained on the split-core sections at a sampling interval of one per section through the Pliocene sediments, and three to four per core below the Pliocene sediments in cores from Hole 1171A, the XCB sections from Holes 1171C and 1171D to a depth of ~754 mbsf (PWS3; x-direction) (Figs. F40, F41). When possible, discrete velocity was measured in longitudinal directions (PWS1; z-direction down to ~ 220 mbsf in Hole 1171A).
A comparison of the MST velocity profile and the discrete velocity values for the interval between 0 and 120 mbsf is shown in Figure F40. All the data sets correlate fairly well, with most values within the range of 1550-1700 m/s. Velocities >3000 m/s correspond to intervals with well-lithified sediments (Units III and IV, Subunit VA, and Unit VI). Average velocities vary from 1550 m/s in the soft-surface sediments to 2400 m/s in the more consolidated sediments (PWS3; Table T21; Fig. F41).
Thermal conductivity was measured on Section 3 of each core in Hole 1171A to a depth at which induration prevented insertion of the needles (~110 mbsf) (Fig. F42; Table T22). Values increase rapidly at ~50 mbsf then slowly decrease with depth.
The Adara tools were deployed three times at Site 1171 and this deployment yielded two acceptable temperature records. The temperature at the seafloor (2.95°C) was determined using the mudline stops. Examination of the penetration temperature records indicates a normal deployment (see "Physical Properties" in the "Site 1168" chapter).
The geothermal gradient determined by least-squares regression is 62°C/km (Fig. F43), compared to 58°C/km at Site 1168 and 52°C/km at Site 1170 (see the "Physical Properties" in the "Site 1168" chapter and "Physical Properties" in the "Site 1170" chapter). Data for all sites show higher values than the Cape Sorell No. 1 exploration well (27°C/km) on the continental shelf 100 km to the northeast of Site 1168 (Willcox et al., 1989). The average of the thermal conductivities measured from 0 through 108 mbsf in Hole 1171C is 1.112 W/(m·K). Using the average conductivity and the geothermal gradient yields a heat flow of 68 mW/m2.
This heat-flow value is twice the values reported from sedimentary basins and slopes near western Tasmania north of Site 1168 and Mesozoic continental margins in the mid-Atlantic (~40 mW/m 2; see "Physical Properties" in the "Site 1168" chapter).
One measurement per section of vane shear strength was taken in Hole 1171A to the depth at which induration prevented insertion of the vane for shear strength (~120 mbsf; the ooze-chalk transition). A clear trend in shear strength is not observed (Fig. F44; Table T23). The values are variable and fluctuate around an average value of ~13 kPa from 0 to 90 mbsf and at ~8 kPa from 90 to 120 mbsf.
Bulk density generally increases with depth below seafloor, whereas porosity and water content decrease (Table T24). Several changes in the MAD gradients with depth are present throughout the section. These gradient changes are usually bounded by offsets that roughly correlate with the boundaries between lithostratigraphic units (see "Lithostratigraphy") and with changes in sedimentation rates (see "Biostratigraphy"). The discrete wet bulk density data (Fig. F45) correlate very well with the GRA data and can be used to calibrate and correct GRA density (see "Multisensor Track"; Fig. F39B). Large fluctuations occur in the MAD records in lithostratigraphic Unit IV, corresponding to alternating intervals of lithified and unlithified sediments (see "Lithostratigraphy").