Measurements of unsplit sections of core taken at Site 1136 were taken from magnetic susceptibility, gamma-ray attenuation porosity evaluator (GRAPE) bulk density, and natural gamma radiation (NGR). We also determined thermal conductivity for sediments and basement rocks. Compressional wave velocities (Vp) were determined on the working half of the core and in discrete samples with the contact/insertion probe system. We calculated index properties from wet and dry sample masses and dry volumes.
We obtained index properties data (bulk density, grain density, porosity, and water content) using gravimetric methods on discrete samples from Site 1136 (Table T11; Fig. F41). Average grain densities of 2.70 g/cm3 and 2.68 g/cm3 for lithologic Unit II (early to middle Eocene foraminifer-bearing nannofossil ooze) and Unit III (mid-Campanian calcareous ooze), respectively, are virtually the same as those of lithologic Units II and III in Hole 1135A (see "Physical Properties" in the "Site 1135" chapter). Between ~90 and ~120 mbsf, within Unit V, grain density decreases to mean value of 2.48 g/cm3. Water content and porosity are also quite uniform within Units II and III. Average porosities of 56.2% and 52.0% are present in Units II and III samples, respectively. Porosity values in Unit V increase to 65.5%.
Sediment and basalt units separate by marked differences in all index properties (Fig. F41). Porosity decreases sharply from an average of ~57% in the overlying sediments to ~16% in the basalt flows. The average grain density of 2.90 ± 0.04 g/cm3 for basaltic Unit VI is slightly less than the average grain density for basalt, 3.01 ± 0.14 g/cm3 (Johnson and Olhoeft, 1984). The slight discrepancy may be caused by less dense clays and calcite filling many of the vesicles and veins within the basalt, as well as alteration in the basaltic flows (see "Alteration and Weathering").
Bulk densities were also estimated from whole-core GRAPE measurements taken in sections recovered from Hole 1136A (Fig. F42). In the sedimentary section, the maximum GRAPE densities are in the uppermost 40 cm in Section 183-1136A-2R-1 at a depth of ~5 mbsf, which coincides with coarse mixed volcanic sand. These mixed sediments are interpreted as mixed ice-rafted debris and ooze that were highly disturbed during coring (see "Lithostratigraphy").
The maximum GRAPE densities give the best estimate for true bulk density of the sediment (Blum, 1997; Boyce, 1973). Maximum densities increase at the lithology boundary of the sediment and basalt units (Fig. F42C). In the sedimentary section, between 5.2 and 55.1 mbsf, the average estimated maximum density is 1.7 g/cm3. Below 70.3 mbsf, which is the boundary between lithologic Units II and III (see "Lithostratigraphy"), the estimated maximum bulk density increases to an average of 2.0 g/cm3. Between 118.4 and 120.6 mbsf, the bulk density decreases to a value of 1.8 g/cm3, corresponding to the highly fractured and altered volcanic sands in Core 183-1136A-14R. Below 128.1 mbsf, recovered cores are basalts that exhibit much higher bulk density with an estimated maximum value of 2.6 g/cm3. Comparison of the downhole maximum bulk density profile (Fig. F42C) and bulk density data obtained from discrete samples (Fig. F41A) shows that the two generally correlate, except that discrete sample data for the basalt units consistently show higher values than the GRAPE density data. The larger scatter in the GRAPE bulk density data for the basalt flows probably results from the fractured nature and narrow diameters of the cores, which consequently do not fill the core liner.
Where sufficient data were present, NGR data obtained from whole-round sections were filtered using a 5-m-wide boxcar function. As shown in Figure F42, NGR measurements on unsplit sections of Hole 1136A show local positive peaks of >20 counts at ~5, ~80, and ~150 mbsf, corresponding to the Pleistocene coarse sand, the Upper Cretaceous calcareous ooze (with minor disseminated volcanic material), and the flow top of basement Unit 2, respectively. In the rest of the section, NGR values vary little. In the sediments, the values drop from an average value of 8 to 2 cps. A local small increase at ~120 mbsf reflects the altered volcanic sand unit (Core 183-1136A-14R). In the basaltic basement (128.1-160 mbsf), NGR averages 5 cps (Fig. F42B).
We determined magnetic susceptibility on all cores from Site 1136, with whole-core sections measured at 4-cm intervals by the Bartington meter and split-half sections at 2-cm intervals by the point-susceptibility meter. The two magnetic susceptibility data sets compare well with each other. The characteristic susceptibility peaks and troughs correlate with flow boundaries, with peaks reflecting flow top and troughs corresponding to flow bottom and intervals with abundant vesicles (Fig. F43A). Detailed results are discussed in "Paleomagnetism", in conjunction with the NRM pass-through and discrete sample measurements.
Variations in compressional wave velocity downhole commonly correlate with changes in lithology. In general, compressional wave velocity bears a direct relation to wet bulk density and grain density and is inversely related to water content and porosity. At Site 1136, we calculated compressional wave velocity from both discrete measurements on split-core sections and cut samples (Fig. F41D). Measurements were generally made in the x direction, although some discrete samples were also measured in the other two directions to investigate velocity anisotropy (Table T12). We observed no clear anisotropy trend (Fig. F43; Table T12).
The compressional wave velocity data for the sedimentary sections show very little scatter (Table T12; Fig. F41D). A marked velocity contrast at a depth of 128.1 mbsf marks the boundary between the sediments and basement. Above 128.1 mbsf, compressional wave velocity are typically <1800 m/s. Within the basalt section, velocities typically exceed 4000 m/s (Fig. F43), with the highest velocities of 5000-6000 m/s corresponding to the bottom of the basement Unit 2 (see "Igneous Petrology"). The high compressional wave velocity close to 6000 m/s in the lowermost basalt unit are related to high bulk density and very low porosity values (Fig. F43). The velocities close to 6000 m/s appear to be unusually high; however, a comparable data range of 5000-6000 m/s was also observed (e.g., in Hole 917A basalts). These data could also be a consequence of the calibration method (see "Physical Properties" in the "Explanatory Notes" chapter).
We determined thermal conductivity on selected lithified sediments and basaltic rock samples from Site 1136 (Table T13). In the sedimentary section, thermal conductivity values show no significant changes with depth. Between 26.2 and 48.1 mbsf, thermal conductivity averages 1.22 W/(m·K), which agrees well with those of samples measured from Hole 1135A (see "Physical Properties" in the "Site 1135" chapter). The basalt, on the other hand, exhibits higher thermal conductivity values ranging between 1.48 and 2.02 W/(m·K) in the depth interval from 130.8 to 157.1 mbsf (Table T13).
The physical properties data obtained at Site 1136 are heterogeneous, reflecting variations in consolidation and lithology. The most significant change is at the contact between the basalts and overlying sedimentary units (Fig. F42A). Variations in physical properties in the overlying sediments suggest smaller-scale heterogeneities in lithology and/or consolidation, although core recovery was poor throughout the sedimentary section.