Natural gamma-ray activity (NGR), magnetic susceptibility, gamma-ray attenuation porosity evaluator (GRAPE) density, and P-wave velocity were measured on whole-round samples (see "Physical Properties" in the "Explanatory Notes" chapter). All measurements were made to the base of the XCB cores in Hole 1101A, to a depth of 217.7 mbsf (Core 178-1101A-24X).
Whole-core magnetic susceptibility was measured at 2-cm intervals (averaged over 2 s). The raw data are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are shown in Figure F25 . The spurious data associated with the ends of sections (see "Physical Properties" in the "Site 1095" chapter) were minimized at Site 1101 by not measuring the upper and lower 6 cm of each section. After low-pass filtering (Fig. F26), depth-scaled susceptibility shows a positive correlation with the GRAPE density data (see "GRAPE Bulk Density"). Paleomagnetic events were used to convert the data to the age scale shown in Figure F27 (filtered after conversion to age scale).
The susceptibility of the sediments increases from ~250 × 10-5 to ~700 × 10-5 SI between 0 and ~67 mbsf (~0.93 Ma). Superimposed on this trend is a quasiperiodic variation in the amplitude of susceptibility with a wavelength of ~12 m. Susceptibility then remains at ~470 × 10-5 SI, although with a higher amplitude quasicyclic variability with a wavelength of ~2.5 m. This character extends down to ~122 mbsf (~1.80 Ma), where the susceptibility drops again, with less consistent variability, to ~300 × 10-5 SI. The above changes match variations in the sedimentology at the site and the broad lithostratigraphic division into three units (see "Lithostratigraphy"). In particular, the susceptibility lows throughout the sequence match higher levels of biogenic material in the sediments. A strong visible match between peaks in magnetic susceptibility and GRAPE density (see "GRAPE Bulk Density") is apparent, although there is no significant statistical correlation between the data sets (correlation coefficient of 0.56 using the program of Paillard et al., 1996).
Density was measured by gamma-ray attenuation (referred to as GRAPE density) at 2-cm intervals (averaged over 2 s at each point). The raw data are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are shown before (Fig. F25) and after (Figs. F26, F27) low-pass filtering.
GRAPE density increases from 1.5 g/cm3 to ~1.85 g/cm3 at 67 mbsf and shows some of the amplitude alternation of ~12-m wavelength seen within the susceptibility record to this depth. The density then varies at 1.85 g/cm3 until 140 mbsf. There is no change in variability of the signal across 67 mbsf, in contrast with the susceptibility signal, in which the amplitude of variation increases below 67 mbsf. Below 140 mbsf, the density varies around a value of 1.65 g/cm3.
The 15 troughs in the GRAPE density signal within lithostratigraphic Unit II (Fig. F26) all correlate with biogenic horizons in the sediments (see "Lithostratigraphy"). Lithostratigraphic Unit I also contains 15 troughs in which the amplitude of variation exceeds 0.05 g/cm3 after the data have been filtered. However, smaller variations are also present, and the troughs are more difficult to determine than in Unit II (Fig. F26).
Whole-core P-wave measurements were made at 2-cm intervals (averaged over 2 s at each point). The raw data are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are shown before (Fig. F25) and after (Figs. F26, F27) low-pass filtering. The data quality is reasonably good to down to 136 mbsf. Below 136 mbsf, biscuiting caused by XCB coring led to data gaps.
P-wave variation is high compared with that at Sites 1095 and 1096, and, for the record down to 136 mbsf, peaks in the data match peaks in the GRAPE density and magnetic susceptibility, although there is no significant correlation between the data sets (correlation coefficient of 0.61 with GRAPE density using the program of Paillard et al., 1996).
Whole-core natural gamma-ray emissions (averaged over 15 s) were counted at 15-cm intervals. The raw data are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are shown before (Fig. F25) and after (Figs. F26, F27) low-pass filtering.
The NGR signal drops from 11 cps at 0 mbsf to ~9 cps at 10 mbsf before rising again to 13.5 cps at 85 mbsf, falling to 8 cps at 170 mbsf, and rising again to 11 cps in the deepest core. This broad trend is interrupted between 63 and 85 mbsf by a drop to 8.5 cps, and between 130 and 200 mbsf by a rise to 14.5 cps.
The broad low-high-low profile of the NGR signal matches similar trends in the magnetic susceptibility and GRAPE density, which suggests that this trend reflects a variation in the content or origin of the nonbiogenic material in the sediments, rather than in any particular size fraction (which might show as a difference between NGR and the other records). Given that grain density (below) does not change in the upper 50 m of the hole, the initial rise in the MST measurements may reflect consolidation in the upper sediment column. There is no consistent relationship between smaller scale NGR variations and the other signals.
Gravimetric and volumetric determinations of index properties were made for 67 samples from Hole 1101A. One sample was taken every first, third, and fifth section of each core, where possible. Samples were not taken from reconstituted sediment surrounding biscuits or in regions of remolded core. Wet mass, dry mass, and dry volume were measured, and from these measurements, percentage water weight, porosity, dry density, bulk density, and grain density were calculated (see "Physical Properties" in the "Explanatory Notes" chapter; data are also provided on CD-ROM and the World Wide Web [see "Related Leg Data" in the Table of Contents]).
Bulk density follows GRAPE density closely (Fig. F28A). Porosity initially decreases downhole (Fig. F28C), as might be expected under consolidation, but rises again below 140 mbsf. Grain density (Fig. F28B) is constant downhole to ~140 mbsf, where it begins to decrease, which suggests a lithologic change that is probably also responsible for the increased porosity. There is a weak positive correlation between total biogenic content and porosity (Fig. F29), which was seen previously at Sites 1096, 1098, and 1099 (see "Physical Properties" in the "Site 1096" chapter, and "Physical Properties", in the "Palmer Deep [Sites 1098 and 1099]" chapter for further explanation).
Discrete P-wave velocity measurements using all three sensors (PWS1, PWS2, and PWS3) of the velocity-strength system were made on cores from Site 1101. The upper 50 m of Hole 1101A (Cores 178-1101A-1H through 6H) were soft enough to use the orthogonal penetrative transducer pairs of PWS1 and PWS2. Additionally, Hamilton Frame measurements (PWS3) were performed at the center of the cross formed by the PWS1 and PWS2 transducer imprints to compare results from all three transducers. Results of all three measurements (PWS1, PWS2, and PWS3) for the upper 50 mbsf are shown in Figure F30. The average spatial resolution of the measurements is ~1 m. The measurements made using transducer pairs PWS1 and PWS2 show very good agreement. No obvious velocity anisotropy is evident in the upper 50 m. The Hamilton Frame measurements (PWS3) taken subsequently at the same locations show higher velocities with a constant offset of ~40 m/s, which we cannot explain.
The velocity at Site 1101 increases linearly with depth (Fig. F31). Local excursions to much higher velocities occur when measurements are taken on small sand and silt layers (at 50.5, 81.0, 93.8, and 206.5 mbsf) or diamictite layers (at 202.3 mbsf). These layers also show the highest signal attenuation. The raw data are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents).
Thermal conductivity was measured once per core, on average, down to ~137 mbsf at Site 1101, usually in the middle of Section 3. Thermal conductivity was used in combination with downhole temperature measurements to estimate heat flow and hence the temperature at the bottom of the hole and the depth to the base of a theoretical methane hydrate stability zone and associated bottom-simulating reflector (BSR), for comparison with Site 1096. Since Site 1101 was drilled only to 217.7 mbsf, such comparison is limited.
All measurements were made by needle probe on the unsplit core, assuming that the core was undisturbed before insertion of the needle and would remain so afterward. For APC cores (i.e., down to 142 mbsf), this assumption is probably correct. No measurements were made in XCB cores (see "Physical Properties" in the "Site 1096" chapter). Thermal conductivity values are low above 22 mbsf and uniformly higher below 31 mbsf. The low values are lower than were measured in the uppermost section at Site 1096. This change does not reflect a lithologic change but may be related to porosity. In the absence of a certain explanation, and because values are mutually consistent, all are accepted as valid. A simple straight-line fit to the data below 31 mbsf (Fig. F32) provides an average thermal conductivity of 1.05 W/(m·K).
The first Adara temperature tool deployment at Site 1101, intended to determine mudline temperature, failed because the APC triggered early. Mudline temperature was measured before firing Core 178-1101A-2H. Additional Adara temperature measurements were made within the sediments after firing Cores 178-1101A-4H, 7H, 10H, and 13H. Temperatures are plotted vs. depth in Figure F33. A straight-line fit to all points except the seafloor measurement (to avoid the effect of the shallow, low-conductivity layer) provides a geothermal gradient of 89.4 ºC/km. With the thermal conductivity calculated above, this gives an average heat flow determination of 93.9 mW/m2, and the lower conductivity at shallow depth brings the temperature-depth curve into good agreement with the measured seafloor temperature. The corresponding depth to a methane hydrate BSR, calculated using Pollution Prevention and Safety Panel (PPSP) (1992) criteria (see "Physical Properties" in the "Site 1096" chapter), is 270 mbsf, well below the base of the hole.
Oceanic basement age at this site, determined from oceanic magnetic anomalies (Larter and Barker, 1991a), is 20.6 Ma, using the time scale of Cande and Kent (1995), although the site is very close to the Biscoe fracture zone, with ocean floor ~2 m.y. older on the other side (see Fig. F4, in Barker and Camerlenghi, Chap. 2, this volume). Allowing for time scale changes from the original work of Parsons and Sclater (1977), the theoretical heat flow for ocean floor of age 20.6 Ma is ~101 mW/m2, ~7% higher than observed. No allowance has been made at this site for the thermal blanketing effect of rapid sedimentation (e.g., Hutchison, 1985).