Index properties, including wet bulk density, grain density, dry bulk density, water content, void ratio, and porosity, were all measured on discrete samples taken from each core recovered in Hole 1183A. Whole sections of all cores were run through the multisensor track (MST), which measured magnetic susceptibility, gamma ray attenuation (GRA) bulk density, and natural gamma radiation (NGR). We measured sonic compressional (P-wave) velocities on cut samples and, where possible, in more than one direction on oriented cubes to investigate velocity anisotropy. Thermal conductivity was measured in unsplit sediment sections and on split rock samples from each core.
We measured the wet mass, dry mass, and dry volume of each sample taken from the core and calculated wet and dry bulk density, water content, grain density, and porosity (Table T14; Fig. F94). The general downhole increase in wet bulk density corresponds to a decrease in porosity and water content with depth of burial. As shown in Figure F94, porosity decreases from 64% to 56% in the ooze and chalk of lithologic Subunits IA and IB (see "Lithostratigraphy"), to 56%-42% in the ash-bed-bearing chalks of Subunit IC, to 52%-25% in the chert- and zeolite-bearing limestone of Unit II, to 45%-14% in the white and gray limestone of Unit III and, finally, to 19%-3% in the basalts of the basement. Little variation in grain density (between 2.6 and 2.8 g/cm3, with a mean value ~2.7 g/cm3) occurs in the sedimentary units (Fig. F94), which agrees with the high and relatively constant CaCO3 content observed downhole (see "Lithostratigraphy"). Bulk density increases sharply near 987 mbsf (the boundary between Subunits IIB and IIIA). This increase appears to correlate with a zeolite-rich chalk zone in the lowest part of Subunit IIB, near the Cretaceous/Paleogene boundary (see "Lithostratigraphy"), where both water content and porosity (Table T14; Fig. F94) also decrease.
We determined magnetic susceptibility with the Bartington meter at 4-cm intervals along all whole-core sections. The results are shown in Figure F95. Magnetic susceptibility was also measured independently every 2 cm on the point-susceptibility meter (see "Lithostratigraphy"). The two magnetic susceptibility data sets compare well with each other. Susceptibility peaks in sedimentary units commonly correlate with lithologic changes, such as the ash layers found in Subunits IC and IIIB. Detailed results are discussed in "Paleomagnetism" in conjunction with discussion of the NRM pass-through and discrete paleomagnetic sample measurements.
We estimated bulk densities from whole-core GRA measurements, which were made in all sections (Fig. F95). The maximum GRA densities give the best estimate for the true bulk densities of the sediments (Blum, 1997). In the ooze and chalk interval of Unit 1, between 328.1 and 836.8 mbsf, the average estimated maximum density is 1.6 g/cm3. Below 838.6 mbsf, which is the boundary between lithologic Units I and II (see "Lithostratigraphy"), the estimated maximum bulk density increases to an average of 1.8 g/cm3 in Unit II. Maximum density abruptly increases at the lithologic unit boundary between sediment and basalt (Fig. F95). In basement, below 1131 mbsf, estimated maximum bulk density reaches an average of 2.6 g/cm3. Comparison of the downhole maximum GRA bulk density profile (Fig. F95) with bulk density data obtained from discrete samples (Fig. F94) demonstrates that the two measurements generally correlate, despite the consistently lower values of the GRA density data. The larger scatter in the GRA bulk density data for the basalts probably is a result of the fractured nature and narrow diameter of the basalt cores, which do not completely fill the core liner. Based on comparison with discrete sample measurements, GRA values <1.6 g/cm3 generally can be disregarded.
NGR measurements on unsplit sections of cores show local peaks of >120 cps, centered at ~420, ~800, and ~965 mbsf (Fig. F95), in the Miocene ooze to chalk of Subunit IB, the Oligocene chalk with ash beds of Subunit IC, and the Paleocene-Eocene zeolite-rich limestone of Subunit IIB. A slight but noticeable increase in NGR counts (256 cps) occurs at 986.3 mbsf, above the Cretaceous/Paleogene boundary in Core 192-1183A-39R. In the basement basalts (1130.4-1211.1 mbsf), the NGR counts generally average 35 cps.
Downhole variations in P-wave velocity commonly correlate with changes in lithology. In general, P-wave velocity varies directly with increasing wet bulk density and grain density and varies inversely with water content and porosity. We calculated P-wave velocity from discrete measurements obtained on both split-core sections and cut samples (Fig. F95) using the contact probe systems. Measurements were generally made in the x-direction, although some oriented cube samples were also measured in the y- and z-directions to investigate velocity anisotropy (Table T15). P-wave velocities in the ooze and chalk sections of Unit I gradually increase from a mean of 1699 m/s in Subunits IA and IB to a mean of 2236 m/s in Subunit IC. A marked velocity increase occurs in Unit II at ~950 mbsf, marking the boundary between the chert-rich limestone of Subunit IIA and the zeolite-rich limestone of Subunit IIB. Above 950 mbsf, P-wave velocities are typically <2500 m/s. Except for portions of Subunit IIIA, velocities below 950 mbsf are typically >3000 m/s (Fig. F95), with the highest values of 3500-4400 m/s at the bottom of Unit II. Although no clear trend in anisotropy is recognizable in Unit I (anisotropy generally is <5%), sediments in Units II and III display velocity anisotropies up to 20% (Table T15). The high P-wave velocities (>5000 m/s) in the basement basalts are associated with high bulk and grain densities and very low porosity values (Fig. F94).
We determined thermal conductivity in unsplit soft sediment cores and on selected samples of lithified sediments and basalt (Table T16). In Subunits IA and IB, thermal conductivity generally is <1.2 W/(m·K), with a median value of 1.1 W/(m·K). In Subunit IC, thermal conductivity generally is >1.5 W/(m·K), with a median value of 1.6 W/(m·K). In the limestone of Subunits IIA, IIB, IIIA, and IIIB, thermal conductivity, although highly variable, generally increases with depth, exhibiting a maximum value of 2.9 W/(m·K) in the bottom of Subunit IIB near the Cretaceous/Paleogene boundary. In basement, the basalts are characterized by somewhat lower thermal conductivity values, ranging between 1.4 and 2.5 W/(m·K) in the depth interval from 1130.3 to 1210.0 mbsf (Fig. F94).