Measurements with the multisensor track (MST) were obtained at 4-cm intervals for gamma-ray attenuation (GRA) bulk density, P-wave velocity, and magnetic susceptibility. Natural gamma radiation (NGR) was measured at 12-cm intervals. No P-wave velocity data were recorded on XCB cores (i.e., below 39.7 mbsf). MST results in XCB cores were degraded in quality because of drilling disturbance associated with coring and incompletely filled core liners. This disturbance is illustrated by a comparison of GRA bulk densities with discrete density determinations (see "Moisture and Density Measurements"). In Figure F28, we present edited MST data from Hole 1167A measured on APC cores (0-40 mbsf). Measurements from deeper intervals may also be useful in discerning lithologic changes but need extensive postcruise editing. This is exemplified by apparent 20-cm-scale cyclic changes in GRA bulk densities, which are pervasive in the XCB-cored part of the hole, and which are the result of spiraling gouges produced by the core catcher on the outer surface of the sample. The MST measurements are available (see the "Related Leg Data" contents list).
GRA bulk density, P-wave velocity, and magnetic susceptibility exhibit similar downhole patterns for the upper 40 mbsf at Site 1167. Throughout lithostratigraphic Unit I (0-5.72 mbsf), these parameters show a large variability (magnetic susceptibility: 90 × 10-5 to 310 × 10-5 SI, GRA bulk density: 1.55-2 g/cm3, P-wave velocity: 1500-1650 m/s), possibly reflecting latest Pleistocene and Holocene glacial-interglacial changes in hemipelagic sedimentation. The transition from Unit I to Unit II is characterized by an abrupt step to higher density (~2.2 g/cm3) and magnetic susceptibility (~300 × 10-5 SI) values. No P-wave data were recorded for this transition. Sediment at the top of lithostratigraphic Unit II (5.72-40 mbsf) displays relatively uniform physical properties with a slight trend to increasing values downhole, a response to gravitational sediment compaction. Offsets from a trend to higher magnetic susceptibilities (~400 × 10-5 SI) occur at 15-16 mbsf and below 35 mbsf. Farther downhole, the magnetic susceptibilities show a sawtooth-like trend that is also apparent in the discrete magnetic measurements (see "Paleomagnetism" for more details).
NGR measurements from Site 1167 vary between 1 and 3 cps (Fig. F29) throughout the hole. The 20-m moving average, however, shows some subtle changes. It is fairly constant for the upper 320 m, except for a slight increase at ~210 mbsf that may be a response to the clay beds found at this level (see "Lithostratigraphy"). Clays normally contain more radioactive elements than sands. The LWD tool (see "Downhole Measurements"), however, indicates a decrease in NGR at ~210 mbsf, a difference that may reflect either the inaccuracies in MST measurements over rather short intervals compared to the LWD tool or different instrumental sensitivities to the various parts of the gamma-ray spectrum. The changes observed at ~210 mbsf in many parameters prompted binning of the NGR spectra above and below 200 mbsf. No significant difference can be seen between these two spectra (Fig. F29). At ~320 mbsf, there is a slight decrease in the NGR values. There are no changes in other physical properties at this level, except for the offset in the ARM and IRM (see "Paleomagnetism").
Gravimetric and volumetric determinations of moisture and density (MAD) were made for 138 samples from Hole 1167A (Cores 188-1167A-1H through 49X). One sample was taken, where possible, from each section of each core. Wet mass, dry mass, and dry volume were measured and used to calculate percentage water weight, porosity, dry density, bulk density, and grain density (see "Physical Properties" in the "Explanatory Notes" chapter; also see the "Related Leg Data" contents list for available raw data).
The grain densities measured at Site 1167 are shown in Figure F30. Eight determinations of grain density were made in lithostratigraphic Unit I (0-5.72 mbsf), giving an average value of 2.70 g/cm3 with a range of 2.65-2.74 g/cm3. Within Unit I, the measured values show no trend with depth.
A total of 130 determinations of grain density were made in lithostratigraphic Unit II (5.72-443.70 mbsf). From 5.72 to 210 mbsf, the mean value is 2.70 g/cm3, with a range of 2.67-2.74 g/cm3 (67 measurements). Over this interval, there is no trend in the values with depth. At ~210 mbsf, the grain density abruptly decreases, and from 210 to 443.70 mbsf, the mean value is 2.69 g/cm3, with a range of 2.66-2.73 g/cm3 (63 measurements).
The porosities measured at Site 1167 are shown in Figure F30. Eight determinations of porosity were made in lithostratigraphic Unit I. Within the unit (0-5.72 mbsf), the porosity decreases sharply with depth, dropping from a value of 68.1% at 0.30 mbsf to 42.3% at 5.54 mbsf. The average value of porosity in Unit I is 59.7%. The decrease in porosity from the top to the bottom of Unit I is attributed to compaction under increasing effective overburden stresses.
A total of 67 determinations of porosity were made from the top of lithostratigraphic Unit II (5.72 mbsf) to 210 mbsf. Within this interval, the porosity decreases with depth, from 41.0% at 6.43 mbsf to ~31% at 210 mbsf. About half of this decrease occurs in the upper 10 m of the unit. At 210 mbsf, the porosity abruptly decreases; from 210 to 443.70 mbsf, the mean value is 27.6%, with a range of 22.7%-31.7% (57 measurements).
Other parameters that are derived from the measured data include bulk density, dry density, water content, and void ratio. Bulk-density and dry density values are presented in Figure F31. Eight determinations of bulk density were made in lithostratigraphic Unit I. Within the unit (0-5.72 mbsf), the bulk density increases sharply with depth, rising from a value of 1.55 g/cm3 at 0.30 mbsf to 2.01 g/cm3 at 5.54 mbsf. The average value of bulk density in Unit I is 1.70 g/cm3. The increase in bulk density from the top to the bottom of Unit I is attributed to compaction under increasing effective overburden stresses.
A total of 67 determinations of bulk density were made from the top of lithostratigraphic Unit II (5.72-210 mbsf). Within this interval, the bulk density increases with depth, from 2.00 g/cm3 at 6.43 mbsf to ~2.19 g/cm3 at 210 mbsf. About half of this increase occurs in the upper 10 m of the unit. At 210 mbsf, the bulk density abruptly increases to 2.21 g/cm3. From 210 to 443.70 mbsf, the mean value is 2.23 g/cm3, with a range of 2.16-2.31 g/cm3 (57 measurements). The bulk density gradually increases with depth, from ~2.21 g/cm3 at 210 mbsf to ~2.25 g/cm3 at 443.7 mbsf.
Water content (as a percentage of dry mass corrected for salt content) and void ratio are presented in Figure F32. These plots show trends similar to those observed in the porosity data.
The decrease in grain density and porosity—and hence in bulk density, dry density, water content, and void ratio—at 210 mbsf correlates with a sharp drop in magnetic susceptibility seen at about the same depth (see "Paleomagnetism"). Analysis of the clasts found in the diamict of Unit II shows that above 210 mbsf more granite and other igneous clasts are present, whereas below 210 mbsf more sandstone clasts are present (see "Lithostratigraphy"). This suggests that the physical property changes observed in the sediment at 210 mbsf are a result of a change of provenance of the diamict, and hence, differing ice-flow configurations.
As described previously in this section (see "Multisensor Track"), bulk-density data were obtained from the GRA bulk densiometer in addition to the discrete MAD measurements. To compare the GRA bulk-density data to the discrete MAD measurements, the GRA data set was cleaned by removing the data points at the top of each core section as well as any data points <1.0 g/cm3. Figure F33A presents the cleaned GRA data, superimposed on the bulk densities computed from the discrete MAD measurements. The plot demonstrates that there is good agreement between the two measurement methods to ~40 mbsf and that below this depth the discrete measurements are consistently higher than the GRA measurements. The ratio of the discrete bulk-density measurements to the GRA measurements for corresponding depths (Fig. F33B) is relatively constant and is equal to 0.975 for APC cores (0-39.7 mbsf) and 1.076 for XCB cores (39.7-443.7 mbsf). These ratios agree well with those determined at Site 1165 (see "Moisture and Density Measurements" in the "Site 1165" chapter). This indicates that different calibration constants should be used for the GRA bulk densiometer depending on the coring method being employed or that GRA measurements on different core types using the same GRA bulk densiometer calibration should be scaled to correct the measurements.
P-wave velocities on split cores were measured at a frequency of one measurement per recovered section. The velocity probes P-wave sensor (PWS1 and PWS2), which allow measurements in z- and y-directions in soft sediments, were used on Cores 188-1167A-1R through 3R. Below 24 mbsf, the sediments became too stiff to insert the probes and P-wave velocities were measured in the x-direction (through the core liner) by using probe PWS3. In some intervals blocks of consolidated sediment were cut out, and the P-wave velocity was measured in x-, y-, and z-directions by using PWS3. The laboratory velocity measurements presented here (Fig. F34) were not corrected to in situ temperature and pressure conditions. Velocity data are compiled in Table T8 (also see the "Related Leg Data" contents list).
From 2 to 60 mbsf (lithostratigraphic Unit 1 and the top of Unit 2), P-wave velocities at Site 1167 increase from 1503 to 1986 m/s, which results in a velocity gradient of 9.7 s-1 and is most likely related to sediment compaction. Below 60 mbsf, the homogeneous sediment composition in lithostratigraphic Unit II is reflected by a relatively uniform P-wave velocity, which increases slightly to values of ~2200 m/s close to the bottom of the hole (445 mbsf). The change in the velocity gradient at 60 mbsf correlates with a significant drop in magnetic susceptibility (see "Paleomagnetism"), which could indicate a general change in sediment composition. No corresponding change, however, is seen in the MAD parameters. The most prominent velocity feature in Unit II is a steplike increase in average velocity from 1986 to 2115 m/s below 181 mbsf, which correlates with a drop in porosity and a change to lower grain density. This feature is possibly caused by a higher quartz content below 181 mbsf, as indicated by XRD results.
A total of 27 automatic vane shear (AVS), 71 fall cone (FC), and 103 pocket penetrometer (PP) measurements were obtained, with results spanning the entire recovered interval (Table T9). Down to 50 mbsf, FC and AVS measurements were taken, whereas FC and PP measurements were made between 60 and 300 mbsf. Below 300 mbsf, the sediment strength was only within the range of PP measurements. The FC measurements gave higher shear strengths than either the AVS and the PP. AVS measurements may be too low because of the lack of confinement of the samples, allowing horizontal deformation and/or cracking of the sediment during vane rotation. The FC and PP gave similar shear strengths at Sites 1165 and 1166. The difference observed in Hole 1167A might therefore be a consequence of the sediment composition below 60 mbsf at this site.
The shear strengths (Cu) increase constantly with depth (Fig. F35), reaching ~600 kPa on sediments from the lower part of the hole. The high value of 1000 kPa at ~420 mbsf is a minimum value for a sample from the core catcher in Core 188-1167A-46X and may be from a carbonate cemented layer.
The ratio between shear strength and effective overburden stress (Cu/p´0) is expected to be between 0.25 and 0.35 for a normally compacted sediment (Fig. F36, shaded region) of intermediate plasticity (Brooker and Ireland, 1965; Andresen et al., 1979). The normalized shear strengths show that the sediments at Site 1167 are normally consolidated in the upper 50 mbsf of the hole. Below the core break between ~50 and 60 mbsf, the normalized shear strength values fall below the expected region and remain so for the rest of the hole. This transition is at the same depth as transitions observed in velocimetry and magnetic susceptibility (see "Paleomagnetism") and may therefore be a result of the composition of the sediments. High silt and sand contents and a predominance of kaolinite in the clay minerals (see "Lithostratigraphy") contribute to low plasticities and may therefore be conducive to reducing the expected normalized shear strengths at this site. Alternatively, the cores may have been slightly disturbed by the drilling and coring process. However, the change from APC to XCB coring at ~40 mbsf (Fig. F36) does not seem to have influenced the shear strength in this hole.
The sediments at Site 1167 reveal a compaction history that is not influenced by loads greater than those of the present sediment overburden.
Thermal conductivity was measured using a full-space needle probe (see "Physical Properties" in the "Explanatory Notes" chapter; also see the "Related Leg Data" contents list for available raw data). Where possible, thermal conductivity was measured twice per core on both APC and XCB cores, usually near the middle of the sections.
A total of 68 thermal conductivity measurements were made (Table T10; Fig. F37). The data show a rapidly increasing thermal conductivity profile through lithostratigraphic Unit I, starting at 1.071 W/(m·°C) at 0.75 mbsf and increasing to 1.395 W/(m·°C) at 3.75 mbsf. This rapid increase is attributed to a corresponding increase in dry density over the same depth interval (see "Moisture and Density Measurements").
At the top of Unit II, the thermal conductivity continues to increase to 2.026 W/(m·°C) at 21.45 mbsf. Similar to Unit I, this increase corresponds to the increase in dry density over the interval 5.95-21.45 mbsf. From 21.45 to 66.55 mbsf, the thermal conductivity decreases to 1.294 W/(m·°C). There is no corresponding change in dry density, nor is there a change in the grain density that might indicate a change in mineralogy.
Below ~70 mbsf, the thermal conductivity abruptly increases to ~1.62 W/(m·°C) and increases slightly with depth to ~1.69 W/(m·°C) at 198.9 mbsf. This trend is interrupted by a pair of thermal conductivities of ~1.86 W/(m·°C) at 151 and 155 mbsf.
At 210 mbsf, the thermal conductivity increases abruptly to 1.89 W/(m·°C). This value is maintained to a depth of 295 mbsf. The abrupt increase at 210 mbsf corresponds to an abrupt decrease in the grain density (see "Moisture and Density Measurements") and is therefore attributed to a change in the sediment mineralogy. This change of mineralogy is also indicated by an abrupt decrease in the magnetic susceptibility at 210 mbsf, associated with a downhole change from coarser (above 120 mbsf) to finer magnetite grains at this depth (see "Paleomagnetism"). Below 295 mbsf to 443.7 mbsf, the thermal conductivity decreases slightly to an average value of 1.77 W/[m·°C]) over the length of the interval.
There are two major changes observed in the physical properties at Site 1167. The first is at 5.9 mbsf at the transition between lithostratigraphic Units I and II and is associated with an abrupt increase in magnetic susceptibility and a change to a lower gradient in density. An increase in the P-wave velocity also appears at this depth, but the PWL data for the transition was not obtained on the MST. The other change is at 210 mbsf, where a downhole decrease in grain density and porosity and an increase in bulk density are found. The change at 5.9 mbsf most likely is due to the combined effect of gravitational compaction and the increasing content of sand down through Core 188-1167A-1H (see "Lithostratigraphy") and into the diamicts of Core 188-1167A-2H. The change of physical properties at 210 mbsf indicates a change in mineralogy as seen in the downhole shift to lower grain density. The bulk mineralogy (Fig. F29) suggests that there is a downward increase in quartz and a reduction in the plagioclase contents at this level. These changes imply that the sediment source area shifted, likely in response to reconfiguration of the glacier drainage on the Antarctic continent.