Index properties were measured on discrete samples taken from most of the cores recovered at Site 1186. We also ran whole sections of these cores through the multisensor track (MST) to measure magnetic susceptibility, gamma ray attenuation (GRA) bulk density, and natural gamma radiation (NGR). Sonic compressional (P-wave) velocities were measured on cut samples and, where possible, in more than one direction, on oriented cubes to investigate velocity anisotropy. Thermal conductivity was measured on split rock samples from most of the cores. Variation in the physical properties measured in the core sections from both sedimentary and basement units at Site 1186 are very similar to those observed at Site 1185.
We measured the wet mass, dry mass, and dry volume of each sample taken from the cores and calculated wet and dry bulk density, water content, grain density, and porosity (Table T12; Fig. F53). The general increase in wet bulk density downhole in the sedimentary sequence corresponds to a decrease in porosity and water content with depth of burial. As shown in Figure F53, porosity decreases from 58% to 46% in the limestone of Unit II and chalk of Subunit IIIA (see "Lithostratigraphy"), to 49%-23% in the light gray and dark brown limestone of Subunit IIIB, and finally to 14%-4% in the basalt of the basement units. In Unit II, between 697.4 and 812.7 mbsf, grain densities generally are between 2.2 and 2.4 g/cm3, with a mean of 2.3 g/cm3, and the mean bulk density is 1.7 g/cm3 (Fig. F53). In Subunit IIIA, the general increase in bulk density observed downhole reflects the effects of increasing depth of burial. The mean grain and bulk density for the subunit are 2.5 and 1.8 g/cm3, respectively. The white to brownish white limestone of Unit IIIB between 930.6 and 966.9 mbsf is characterized by the highest grain and bulk density (2.6 and 2.0 g/cm3, respectively). Below 966.85 mbsf, in the basalt of basement Unit 1, bulk density increases to an average of 2.7 g/cm3. Bulk densities in basement Unit 3 are slightly lower than in other basement units. In general, both grain and bulk density decrease downhole in Unit 3, corresponding to a lithologic change from dense basalt to heavily veined basalt. Below the top of Unit 4 (Section 192-1186-36R-4), an increase in bulk density correlates with a change from the veined basalt back to dense basalt.
We determined magnetic susceptibility with the Bartington meter at 4-cm intervals along whole-core sections from most of the cores. The results are shown in Figure F54 and discussed in "Paleomagnetism" in conjunction with the NRM pass-through measurements. Magnetic susceptibility was also independently measured every 2 cm on the archive multisensor track (AMST) with the point-susceptibility meter (see "Lithostratigraphy"). Although susceptibility peaks in sedimentary units commonly correlate with lithologic changes, such as the ash layers in Unit II (near 803 mbsf) and at the boundary between Subunits IIIA and IIIB (at ~930 mbsf), comparison of the two magnetic susceptibility data sets revealed several intervals where magnetic susceptibility spikes in the MST record were absent from the AMST profile (Fig. F55). Close examination of the archive-half core liners revealed that, in each instance, the spikes in the MST record corresponded to an accumulation of grit in the liner at the interval in question. This was probably caused by lost core catcher "dogs" that were ground up on the bottom. Although the source of the grit is unknown, we strongly caution future leg participants to be aware of this problem, especially on sediment drilling legs with paleoclimate objectives.
We estimated bulk densities from whole-core GRA measurements (Fig. F54). In Unit II, in the limestone with chert between 697.5 and 803.8 mbsf, the average estimated maximum density is 1.6 g/cm3, slightly lower than that determined from the index samples obtained from this unit (Fig. F53). In Subunit IIIA, between 832.2 and 930.5 mbsf, bulk density ranges from 1.1 to 2.0 g/cm3, with a mean value of 1.7 g/cm3 (Fig. F54). Below 930.6 mbsf, the bulk density increases downhole to an average of 1.8 g/cm3 in Subunit IIIB. In basement, the mean bulk densities of the sparsely veined basalt (>2.4 g/cm3) in Units 2 and 4 are higher than those of the veined pillow basalt (<2.4 g/cm3) in Units 1 and 3 (Fig. F54). These results are similar to those for Site 1185, where the dense, massive basalt also exhibited higher GRA densities than the more altered and abundantly veined basalt.
Although NGR measurements on unsplit sections of cores from Hole 1186A generally show only minor fluctuations downhole (usually below ~2 counts per second [cps]), a few peaks are present in the NGR profile (Fig. F54). For example, in sedimentary Unit II, peaks of >3 cps at ~698 and ~804 mbsf appear to correspond to the ash layers in Cores 192-1186A-3R and 13R, respectively. In Subunit IIIA, a slight peak ~840 mbsf may correlate with a peak in the gamma logs of the wireline-log data (see "Downhole Measurements". In Subunit IIIB, several peaks >3 cps probably correspond to the brown claystone layers observed (see "Lithostratigraphy"). In the basement units, NGR variations are minor, with the highest count rate (>5 cps) occurring in the pillow basalt of Unit 3 (Fig. F54).
We calculated P-wave velocity from discrete measurements on both split-core sections and cut samples (Table T13; Fig. F54). P-wave velocities in the chert and limestone of Unit II and the nannofossil chalk of Subunit IIIA average 1757 and 1731 m/s, respectively. A velocity increase occurs at 947.9 mbsf in the brown limestone of Subunit IIIB (Fig. F54). Between 931.1 and 966.6 mbsf in Subunit IIIB, P-wave velocities range from 1875 to 2649 m/s, with a mean of 2197 m/s. In the basement units, P-wave velocities are typically >5000 m/s in the less veined basalt of Units 1, 2, and 4 and generally <5000 m/s in the more veined basalt of Unit 3 (Fig. F54). The high P-wave velocities (>5000 m/s) in the relatively unveined basalts are also associated with high bulk and grain densities and low porosity values (Fig. F53).
We determined thermal conductivity in unsplit soft-sediment cores and on selected samples of lithified sediment and basalt (Table T14; Fig. F53). In Units II and III, thermal conductivity generally is <1.2 W/(m·K). In the basalt from the basement units, thermal conductivity remains fairly constant downhole (Fig. F53). The average thermal conductivity for the basement units is 1.8 W/(m·K), similar to the basement basalt of Site 1185.