Measurements on whole-round core sections taken in Hole 1151A included magnetic susceptibility, gamma-ray attenuation (GRA) bulk density, NGR activity, and thermal conductivity. P-wave velocity and index properties measurements were made on what appeared to be the least-disturbed portions of split core sections. Hence, sampling was biased in favor of indurated sections. The P-wave logger (PWL) and vane shear apparatus were not used in Hole 1151A because RCB sediments are not of appropriate quality. Only multisensor track (MST) data were acquired on whole-round core sections from Holes 1151C and 1151D. Thermal conductivity, P-wave velocity, shear strength, and index properties were not measured because of time constraints, which also forced us to conduct the MST measurements before the cores had equilibrated to ambient laboratory room temperature. Descriptions of the experimental methods are in "Physical Properties" in the "Explanatory Notes" chapter.
Magnetic susceptibility was measured with a 2-cm sampling interval on all cores recovered in Hole 1151A and with a 5-cm sampling interval on cores from Holes 1151C and 1151D. The results of magnetic susceptibility measurements are discussed in "Paleomagnetism". GRA bulk density was measured with a 2-cm sampling interval on all cores from Hole 1151A, and with a 5-cm sampling interval on cores recovered in Holes 1151C and 1151D. In addition, a number of whole-round core sections from Hole 1151A (i.e., Sections 186-1151A-69R-4, 105R-2, 106R-5, and 108R-2) were rerun with a 1-cm sampling interval to aid the selection of suitable whole-round core samples for postcruise laboratory tests. Preliminary shipboard analyses included editing of density data by removing values <1.0 g/cm3. The maximum GRA bulk density is reported here because it is assumed to provide the best estimate of bulk density.
The maximum GRA bulk density in Hole 1151A has a total range from ~1.3 to 2.0 g/cm3 (Fig. F29). Corresponding ranges for the variation in Holes 1151C and 1151D are 1.2 to 1.8 g/cm3 and 1.2 to 2.1 g/cm3, respectively. Density increases from 1.2 g/cm3 at the mudline to 1.7 g/cm3 at 15 mbsf. After this local maximum, density decreases to ~1.4 g/cm3 at 190 mbsf. Lithologic Unit II (190-430 mbsf; see "Lithostratigraphy") is characterized by rather constant values, averaging at ~1.4 g/cm3. Density varies from 1.3 to 1.7 g/cm3 along an oscillating trend in lithologic Unit III (430-911 mbsf). Local peaks occur at ~450, 570, 590, 810, and 900 mbsf, and local troughs occur at ~530, 670, 800, and 850 mbsf. Similar oscillating trends are observed in lithologic Units IV and V (911-1007 mbsf and 1007-1113 mbsf, respectively). However, the range of values is greater in lithologic Unit IV (1.3-1.8 g/cm3) and greater and more scattered in lithologic Unit V (1.4-2.0 g/cm3).
P-wave velocity in the horizontal direction was acquired with the PWL on full sections for Holes 1151C and 1151D. The cores in this interval were severely disturbed by gas expansion, which resulted in mechanical stretching and micro- to macrofracturing of the cores. As a result, PWL measurements generally are of poor quality. After the preliminary shipboard processing (see "Physical Properties" in the "Explanatory Notes" chapter), the results of PWL measurements included data from the upper 20 and 22 m of Holes 1151C and 1151D, respectively. P-wave velocity ranges from 1450 to more than 5000 m/s, although most values vary between 1450 and 1600 m/s (Fig. F30). Higher velocities generally are obtained near the edges and voids of core sections and are assumed to be artificial.
NGR activity was measured every 20 cm with 20-s-long counting periods on all cores recovered at Site 1151 and reported in counts per second (cps) with the total background radiation subtracted (12.27 cps). The maximum values at each depth of NGR activity are reported here.
NGR activity has an overall range from 5 to 29 cps in Hole 1151A. Corresponding ranges for the variation in Holes 1151C and 1151D are 9-36 and 10-40 cps, respectively. The downhole variation generally has a width of scatter of ~5 cps (Fig. F31). The downhole trend correlates with that of GRA bulk density. NGR activity increases from 15 to 27 cps in the upper 15 m of Holes 1151C and 1151D and then begins a decreasing trend to 12 cps at 190 mbsf. From ~250 to 1114 mbsf, NGR activity generally increases with depth. NGR activity generally ranges from 10 to 15 cps in lithologic Unit II (190-430 mbsf). Lithologic Units III through V are characterized by oscillating trends. The former unit has lower and somewhat less scattered values that generally range from 11 to 21 cps compared to the two latter ones, for which the NGR activity ranges from 13 to 25 cps.
Thermal conductivity was measured at a frequency of one measurement per core from 79 to 413 mbsf in Hole 1151A using the full-space configuration. The mean error associated with these measurements is assumed to be 0.2 W/(m·K). The average thermal conductivity, which was obtained from three measurements, ranges from <0.4 to ~0.9 W/(m·K) (Fig. F32; Table T14, also available in ASCII format). The maximum and minimum values were obtained in the first two measurements of Hole 1151A cores. Below, a generally fluctuating downhole trend is measured, with breaks in the slope at ~150 and 300 mbsf. A poor correlation is obtained for thermal conductivity vs. porosity and bulk density, indicating that the quality of data is deteriorated by drilling disturbances.
P-wave velocity was mainly measured in split cores from Hole 1151A with the PWS3 system. We aimed at a sampling frequency of one measurement per section. However, because of scattering and attenuation of the signal in the sediment specimen, the PWS1 system yielded good data for only two measurements at ~80 mbsf (Table T15, also available in ASCII format), and the PWS3 system was used downhole only from ~250 mbsf. P-wave velocity values <1450 m/s were omitted. PWS3 measurements were made on indurated pieces (305-413 mbsf) and on cylindrical minicores (247 and 422-1113 mbsf). For the latter, P-wave velocity was measured in three directions, allowing estimation of acoustic anisotropy. P-wave velocity and index properties data were measured on the same sample.
In Hole 1151A, horizontal and vertical velocity has overall ranges from ~1540 to 5290 m/s and ~1450 to 5010 m/s, respectively (Fig. F33; Table T15). However, the majority of measurements indicate P-wave velocities <2150 m/s. Greater velocities were measured in thin beds of dolomite, dolomite concretions, and carbonate-rich sediments. Three measurements of horizontal and vertical velocity at ~80 mbsf yield the lowest values of Hole 1151A (<1480 m/s). Horizontal velocity increases from ~1550 at 305 mbsf to 1640 m/s at 425 mbsf in lithologic Unit II (Fig. F33A). Lithologic Unit III (430-911 mbsf) is characterized by steadily increasing horizontal velocity from ~1600 to 1800 m/s. Below 600 mbsf, the values generally are scattered by ~200 m/s. The vertical velocity shows a similar trend, but with lower values than the horizontal velocity, and generally increases from 1580 to 1750 m/s in lithologic Unit III (Fig. F33B). Below 911 mbsf, somewhat fluctuating trends in horizontal and vertical velocity were measured. Horizontal and vertical velocities increase to ~2100 and 2000 m/s, respectively, at the base of Hole 1151A. There are two zones with increased scatter and higher velocity values, namely from 893 to 970 mbsf, and from 1058 to 1113 mbsf. Maximum horizontal and vertical velocities in Hole 1151A (5290 and 5010 m/s, respectively) were measured on a dolomite concretion at 1108 mbsf.
Acoustic anisotropy was calculated from measurements of P-wave velocity in the x, y, and z directions on cylindrical minicores (see "Physical Properties" in the "Explanatory Notes" chapter). Three anisotropy values were determined, namely maximum vs. minimum horizontal velocity (AHh), maximum horizontal vs. vertical velocity (AHV), and minimum horizontal vs. vertical velocity (AhV). Anisotropy in the horizontal direction (AHh) ranges from 0 to 0.15, although the majority of values are less than 0.05 (Fig. F34A). Furthermore, the AHh anisotropy tends to become more scattered with depth. The ranges of AHV and AhV are -0.05-0.19 and -0.08-0.12, respectively. However, the vast majority of these measurements (>90%) have positive values. The results suggest that the sediments at minimum are transverse isotropic but that they probably are anisotropic. The preliminary shipboard analyses did not include investigations of the variation of horizontal anisotropy (AXY) with azimuth using paleomagnetic declination data.
Index properties were determined on discrete samples recovered from Hole 1151A using gravimetric methods. A dedicated program calculates the index properties from wet and dry mass and dry volume, using a salinity of 0.035 and a pore-water density of 1.024 g/cm3. At this site, the salinity and density of the pore water were significantly different (0.032-0.018 and 1.023-1.012 g/cm3, respectively). Index properties were recalculated using in situ values of salinity and pore-water density from linear extrapolation of 34 measurements on interstitial pore-water samples (see "Geochemistry"; see also "Physical Properties" in the "Explanatory Notes" chapter). Figure F35 shows variation with depth of the ratio of index properties corrected for in situ salinity and pore-water density over those determined with standard salinity and pore-water density. The different salinity and pore-water density values have only a minor influence on bulk density and grain density (the ratio ranges from 0.98 to 1.02); however, they have intermediate influence on dry density, porosity, and void ratio (the ratio ranges from 0.96 to 1.04), and significant influence on water content of total mass, and water content of mass of solids (the ratio ranges from 0.93 to 1.07). Index properties determined from in situ variations of salinity and density of pore water are reported here. Note that index properties included in the Janus database are calculated from standard values of salinity and pore-water density.
To cross-examine the internal quality of the data, porosity, dry density, and void ratio were calculated indirectly from the other index properties (see "Physical Properties" in the "Explanatory Notes" chapter). The direct and indirect calculations of dry density, porosity (i.e., Equation 9 in "Physical Properties" in the "Explanatory Notes" chapter) and void ratio overlap perfectly (i.e., 0% difference), whereas the difference between direct and indirect determination of porosity (i.e., Eq. 10 in "Physical Properties" in the "Explanatory Notes" chapter) is <2%. These differences lie within the estimated uncertainty of index properties measurements (±2%), which implies good quality of index properties measurements.
The overall plots of index properties vs. depth indicate that sediments at this site are porous and poorly consolidated. Exceptions from these trends are obtained from measurements of dolomite samples that appear to be well consolidated. The main results of the downhole variation in porosity, bulk density, and grain density are presented below. Water content and void ratio have downhole trends similar to that of porosity, and dry density has a downhole trend similar to that of bulk density (Fig. F36; Table T16, also available in ASCII format).
The overall ranges of porosity, bulk density, and grain density in Hole 1151A are 10%-77%, 1.32-2.42 g/cm3, and 2.09-3.91 g/cm3, respectively. Generally, samples with low porosity (<40%) and high bulk density (>1.8 g/cm3) consist of dolomite or carbonate-rich sediment. The section from 78 to 347 mbsf has scattered but slightly inverse trends of porosity and bulk density; porosity and bulk density generally range from 57% to 77% and from 1.3 to 1.6 g/cm3, respectively. At 190 mbsf, there is a small decrease in the width of the scatter of porosity and bulk density values and some of the measurements indicate slightly increasing porosity and decreasing bulk density from 190 to 347 mbsf (Fig. F36; Table T16). Grain density variation from 78 to 347 mbsf is more scattered and ranges from 2.09 to 2.67 g/cm3. Between 347 and 430 mbsf, index properties show normal downhole trends. Porosity decreases from ~76% to 65%, bulk density and grain density increase from 1.34 to 1.65 g/cm3 and 2.31 to 2.42 g/cm3, respectively. There is a drop to slightly more scattered and lower porosity and higher bulk density in the section from ~410 to 450 mbsf. Below ~450 mbsf, the trends of index properties show normal and uniform changes with depth. At 719 mbsf, porosity is ~60% and bulk density is ~1.6 g/cm3. Rather constant values of porosity (58%-65%) and bulk density (1.46-1.65 g/cm3) are measured from 719 to 812 mbsf. Index properties change significantly in the interval from 812 to 897 mbsf. Porosity reaches a local minimum of 50% at 812 mbsf and a local maximum of 69% at 849 mbsf. Bulk density and grain density values mirror the trend of porosity and show a local maximum at 812 mbsf (1.58 and 2.40 g/cm3, respectively) and a local minimum at 849 mbsf (1.38 and 2.20 g/cm3, respectively). Yet another section of constant index properties values is measured from 897 to 962 mbsf; porosity and bulk density averages are 58% and 1.6 g/cm3, respectively. This is followed by more scattered values. The section from 962 to 1007 mbsf has higher porosity, whereas the section from 1007 to 1114 mbsf has lower porosity. At the base of Hole 1151A, porosity, bulk density, and grain density are 49%, 1.75 g/cm3, and 2.46 g/cm3, respectively.
The total and effective vertical stress were calculated from bulk density and porosity data following Equations 13 and 8 in "Physical Properties" in the "Explanatory Notes" chapter. The bulk density data consisted of GRA bulk density data from 0 to 97 mbsf, discrete measurements of bulk density in cores from 78 to 1113 mbsf, and hostile environment lithodensity sonde (HLDS) bulk density from 111 to 858 mbsf. GRA and HLDS bulk density data were converted into porosity using Equation 9 in "Physical Properties" in the "Explanatory Notes" chapter. Grain density values were estimated from linear extrapolation of discrete grain density measurements in cores, and pore-water density was assumed to be 1.024 g/cm3. The total and effective vertical stresses increase uniformly with depth to 16.8 and 9.8 MPa at 1113 mbsf, respectively. The downhole trends of vertical stresses are rather linear, with subtle changes in the slope at ~100 and 730 mbsf (Fig. F37).
In general, the various shipboard analyses of physical properties show similar downhole trends. There is a good fit between GRA and discrete bulk density measurements in the upper 700 mbsf, whereas GRA measurements are 0.1 to 0.2 g/cm3 lower than discrete measurements below 700 mbsf. This could result in part from biased sampling of index properties samples. However, the discrepancy between GRA and discrete values probably also results from the fact that the deeper RCB cores did not completely fill the core liner. This would result in underestimation of GRA bulk density (Blum, 1997). The shallow RCB cores were disturbed by drilling and often comprised drilling biscuits. This has resulted in low quality of thermal conductivity data, which is confirmed by the poor correlation between thermal conductivity vs. porosity and bulk density. In Holes 1151C and 1151D, the quality of P-wave velocity (PWL measurements) is degraded by the presence of micro- and macrofractures in many of the APC cores. These fractures were formed by gas expansion in the cores when they were recovered to the drill floor. The remaining physical properties appear to correlate well with each other. Tests of internal consistency of index property data confirm the good-quality index properties.
Site 1151 is characterized by minor to moderate variations in physical properties reflecting the generally homogeneous lithology, with the exception of a few large excursions in the data. Apart from the excursions, which were taken from dolomite or other carbonate-rich layers or nodules, the downhole variations of physical properties are generally similar at Sites 1150 and 1151. Lithology in Site 1151 is dominated by varying amounts of greenish hemipelagic diatom-bearing clay and silt that become indurated with depth. The variation of physical properties data with depth is marked with anomolous values and/or changes in the downhole trend that generally can be correlated with lithologic units (see "Lithostratigraphy"). The breaks in physical properties data appear mainly to signal variations in mechanical conditions (i.e., induration of sediments) (Figs. F29, F31, F33, F36).
The upper 78 mbsf of the section was cored only in Holes 1151C and 1151D and not in Hole 1151A. Lithologic Unit I (0-190 mbsf) is largely composed of soft Pleistocene and Pliocene diatom-bearing silty clays. GRA bulk density variation in the upper 15 mbsf of this interval suggests decreasing values with depth, whereas increasing values are measured below 15 mbsf (Fig. F29). The base of lithologic Unit I coincides with a distinct change to higher NGR activity and a small decrease in the width of scatter of index properties data (Figs. F31, F36).
Lithologic Unit II (190-430 mbsf) consists of soft diatomaceous and spicule-bearing to diatomaceous silty clay. The unit is divided into three subunits based on the induration of the sediment (see "Lithostratigraphy"), of which NGR activity and index properties data (Figs. F31, F36) signal the boundary between Subunits IIA and IIB (295 mbsf) and index properties data signal the boundary between Subunits IIB and IIC (347 mbsf). The section from 78 to 347 mbsf generally has constant index properties, suggesting that the section is underconsolidated. Below 347 mbsf, normal trends (decreasing porosity and increasing bulk density) are measured.
The top of lithologic Unit III (430-897 mbsf) is marked by a local drop of porosity, which is followed by a small change to higher porosity; bulk density shows the inverse trend to that of porosity. This is followed by normal trends to 719 mbsf (i.e., boundary between lithologic Subunits IIIB and IIIC) where the induration of cores changes from a mix of soft and firm sediment to firm sediment. The gradients of downhole change of index properties is similar in the sections from 347 to 430 mbsf and ~450 to 719 mbsf, suggesting that the section from 347 to 719 mbsf is normally consolidated. This sequence is mainly composed of firm diatom-, spicule-, and glass-bearing silty clay of early Pliocene to late Miocene age. Existing P-wave velocity data in this interval show uniformly increasing values to ~600 mbsf (Fig. F33). P-wave velocity becomes significantly more scattered below, probably reflecting increasing influence of brittle deformational structures (see "Lithostratigraphy"). Lithologic Subunit IIIC (719-897 mbsf) is mainly composed of upper Miocene diatom-, glass-, and spicule-bearing silty claystone. The porosity and bulk density is rather constant throughout the unit, suggesting that this section is underconsolidated. Dewatering of the section is probably hindered by the rapid deposition (250 m/m.y.) and impermeable nature of the overlying sediment section (see "Sedimentation Rates").
Sediments of lithologic Unit IV (897-1007 mbsf) are classified as hard, and they are mainly composed of upper Miocene silty claystone that is diatom-, glass-, and/or spicule-bearing (see "Lithostratigraphy"). The upper 63 m of the unit is characterized by almost constant porosity and bulk density, whereas the sediment is less consolidated (higher porosity, lower bulk density) in the lower section of lithologic Unit IV. The interval between 962 and 1007 mbsf does not correspond to changes in lithology, chemistry, or biostratigraphy. However, the core recovery was very low (1.1-m-long core), and the bedding dips increase significantly near this depth (see "Bedding"). This indicates that there is an unconformity at this depth.
Lithologic Unit V (1007-1114 mbsf) is characterized by significantly lower porosity and higher bulk density and P-wave velocity (Figs. F33, F36).