Natural gamma-ray activity, magnetic susceptibility, gamma-ray attenuation porosity evaluator (GRAPE) density, and P-wave velocity were measured on whole-round core sections (see "Physical Properties" in the "Explanatory Notes" chapter). All measurements were made to the base of the cores in Holes 1098A, 1098B, and 1098C to depths of 44.98 mbsf (Core 178-1098A-6H), 44.1 mbsf (Core 178-1098B-5H), and 45.17 mbsf (Core 178-1098C-5H), respectively. At Site 1099, GRAPE density, susceptibility, and natural gamma radiation (NGR) measurements were made to the base of Holes 1099A and 1099B at depths of 62.38 mbsf (Core 178-1099A-7H) and 107.62 mbsf (Core 178-1099B-5H), respectively. P-wave velocity was measured to the base of Hole 1099A at 62 mbsf and to 69.0 mbsf in Hole 1099B (Core 178-1099B-1H).
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) for Sites 1098 and 1099. The raw data from Hole 1098C, which was the most continuous of the three holes and apparently covered the greatest stratigraphic range, and the record for Site 1099 are presented in Figures F26 and F27.
The susceptibility record shows broad intervals of alternating high and low susceptibility (Site 1098 highs are at 0-8 and 30-38 mbsf, and Site 1099 highs are at 0-8, 24-40, and 70-75 mbsf). The low values in the upper 8 m of Hole 1098C coincide with laminated (nonbioturbated) layers. Only one obvious magnetic susceptibility low (at ~4 mbsf) does not correlate with a nonbioturbated region; there is no visible lamination on the split-core surface. The GRAPE density correlates strongly with the magnetic susceptibility (Fig. F28; correlation coefficients of 0.81 and 0.72 for the records are shown in Figures F26 and F27, using programs from Paillard et al., 1996). Within this upper record are variations that have been correlated with climatic cycles of ~2500 and 200 yr by Leventer et al. (1996).
The variability in magnetic susceptibility seen in Core 178-1098C-1H disappears downcore at 9 mbsf, with values dropping steadily to 9 × 10-5 SI (Fig. F28). These lows in susceptibility and GRAPE density are again associated with the laminated (nonbioturbated) diatomaceous ooze. The diatom-rich laminae contain better preserved diatom chains and spines than the bioturbated units (see "Biostratigraphy"). It is therefore likely that the low values of density and susceptibility reflect a semi-interlocked skeleton of biosiliceous material. In such a material, porosity is not linearly related to overburden stress, and consolidation does not occur until the overburden stress reaches the yield strength of the diatom chain-links and spines that support the skeleton. The homogeneity of the diatom species and limited size range (see "Biostratigraphy") in these layers also allow a more porous structure to develop in the same manner as a well-sorted granular sediment. The high water content resulting from these processes reduces the bulk density and magnetic susceptibility. More importantly, susceptibility and magnetic intensity are influenced by the change in the composition of magnetic minerals (see "Paleomagnetism").
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) for Sites 1098 and 1099. Hole 1098C and Site 1099 data are shown in Figures F26 and F27, respectively.
The density increases down through the sediments at both sites and further increases steeply below 42 mbsf in Hole 1098C, where the lithology of the sediments changes (see "Lithostratigraphy"). Superimposed on this broad trend in Hole 1098C are a decrease in density variability and an increase in density and susceptibility between 24.4 and 28 mbsf, which correspond to a turbidite. However, the higher variability in GRAPE density below 30 mbsf at both sites may be an artifact of gas expansion in the sediments in the laboratory.
The raw data are given on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents). Hole 1098C data are presented in Figure F26. The P-wave velocities are low, as is typical of diatomaceous sediments with a high water content. Velocity decreases between 24.4 and 28 mbsf in Hole 1098C, coincident with increased GRAPE density and the greater sorting and dilution of diatomaceous material within a turbidite (see "Lithostratigraphy"). The P-wave data from Hole 1099A are of poor quality because of the extensive presence of gas in cores and show an increase of P-wave velocities only from 1540 to 1570 m/s between 2 and 20 mbsf.
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). Hole 1098C and Site 1099 data are given in Figures F26 and F27, respectively.
The NGR record is roughly constant (at 12-16 cps) in Hole 1098C, with an increase below 42 mbsf where the lithology changes significantly (see "Lithostratigraphy"). Site 1099 shows a broad trend of decreasing NGR emissions down to 73 mbsf, after which the emissions remain at ~7 cps. The variation may reflect charging of the sediments with radioisotopes as the basins became increasingly influenced by open-marine conditions at the seafloor with time (see "Biostratigraphy"). Alternatively, the variation may reflect a lithologic change in the composition of the terrigenous fraction or a diagenetic alteration of clays.
The NGR record shows little correlation with either GRAPE density (correlation coefficients of 0.52 and -0.29 for Hole 1098C and Site 1099, respectively) or magnetic susceptibility (0.48 and -0.16), although any strong correlation would be masked by the lower NGR sampling frequency.
Gravimetric and volumetric determinations of index properties were made for 17 samples in Hole 1098C, 20 samples in Holes 1099A, and 15 samples in Hole 1099B. Three to four samples were taken per core where appropriate.
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; see "Related Leg Data" in the Table of Contents for raw data). The results for bulk density, grain density, and porosity are given in Figures F29 and F30.
Bulk density from the GRAPE and the index properties bulk density (Figs. F29A, F30A) correlate strongly for both sites. The porosity remains constant in the upper 20 mbsf at Holes 1098C and 1099A, which may reflect the large, well-preserved biogenic component. Below this depth, porosity decreases. In Hole 1098C, grain density increases steadily below 20 mbsf, which suggests a lithologic change that may be reflected in the porosity (for example, a reduction in biogenic material). The relationship is less apparent at Site 1099.
Discrete P-wave velocity measurements were performed on all cores from Hole 1098C using the Hamilton Frame (PWS3) transducers of the velocity-strength system. The raw data set is provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents) and displayed in Figure F31A. The average spatial resolution of the measurements is 1.5 m. In general, the velocities are low (~1560 m/s) with no velocity contrasts in the upper two-thirds of the hole. The increase and stronger contrast in P-wave velocity in the lower part of Hole 1098C coincide with silty and sandy turbidite layers.
Discrete P-wave measurements were also made on Cores 178-1099A-1H through 7H and on Cores 178-1099B-1H and 2H. This data set is provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and displayed in Figure F31B. The average spatial resolution of the measurements is 1.4 m. The velocities in the upper part of Hole 1099A (0-20 mbsf) are low (below 1560 m/s) with only small variations. The increase in variability between 20 and 30 mbsf is related to interbedded thin graded silts (see "Lithostratigraphy"). The velocity peak between 37 and 40 mbsf is derived from measurements in thin (<4 mm) gray diatom laminae, suggesting a species- or concentration-dependent velocity response in the biogenic material as compared with the MST data. A "low velocity" zone between 42 and 55 mbsf correlates with more bioturbated sections in Cores 178-1099A-5H through 7H (see "Lithostratigraphy").
The exsolution of gas and consequent expansion of cores from below 70 mbsf caused a complete attenuation of the acoustic signal. This zone appeared to be one of slightly larger grain size.
Thermal conductivity was measured once per core, on average, for almost all holes at Sites 1098 and 1099, usually in the middle of Section 3 and always by the needle-probe method (see "Physical Properties" in the "Explanatory Notes" chapter). Thermal conductivity was used at these sites, in combination with downhole temperature measurements, to estimate heat flow and the temperature at the bottom of the hole.
Measured thermal conductivity values at both sites are extremely low. Porosities at these sites are very high (see "Split-Core Measurements", Figs. F29, F30), ~85% in the upper 20 m at both sites, so that low values of thermal conductivity, approaching that of salt water, are reasonable. However, values from cores in Hole 1099B, below 60 mbsf where porosities are ~70% (above), are among the lowest measured; it is therefore not clear whether all of these measurements are valid. From core images it is evident that free gas was present in these cores in the laboratory, which may have reduced thermal conductivity (see also "GRAPE Bulk Density" and "P-wave Velocities"). At this preliminary stage, bearing in mind the few temperature measurements made (below), an average value of thermal conductivity for each hole of 0.71 W/(m·K) has been assumed, which is reasonably compatible with the data (Figs. F32, F33).
Temperature measurements were made by the Adara temperature tool at the mudline of both sites, and at two other depths in Hole 1098B and one in Hole 1099A. The temperature gradients (assumed constant at both sites) are 0.103ºC/m at Site 1098 and 0.064ºC/m at Site 1099. With so few measurements of temperature and uncertainty in the thermal conductivity measurements, only approximate determinations of heat flow are possible. Nevertheless, they are clearly different: heat flow at Site 1098 is about 73 mW/m2, whereas at Site 1099 it is 45 mW/m2.