Physical properties measurements of whole-core sections from Hole 1137A using the multisensor track (MST) included magnetic susceptibility, gamma-ray attenuation porosity evaluator (GRAPE), bulk density, and natural gamma radiation (NGR) measurements. We determined compressional wave velocities (Vp) from the split cores in transverse x directions for soft sediments in liners and for hard-rock pieces without the liner. Measurements in the longitudinal (z) and transverse (x and y) directions on cut samples of consolidated sediment and hard rocks were done when possible. Index properties determinations included bulk density, water content, porosity, and grain density. We also routinely determined thermal conductivity for sediment and basalt. Finally, we compared velocities, bulk densities, and porosities with logging data and results.
We determined index properties using gravimetric methods (Table T16; Figs. F81A, F81B, F81C, F82B, F82C, F82D). The sedimentary sections of lithologic Units I and II yielded fairly smooth downhole trends in grain density, bulk density, and porosity. Grain densities in Units I and II are generally between 2.6 and 2.7 g/cm3; these are significantly more scattered than those of coeval units in other Leg 183 sites (see "Physical Properties" in the "Site 1135" chapter). In Cores 183-1137A-2R through 12R, radiolarians may cause the low grain densities, but because carbonate contents within Units I and II are consistently >90% (see "Lithostratigraphy"), we cannot conclude that variable grain densities are caused alone by differences in siliciclastic or siliceous biogenic components and patches of disseminated pyrite. Further investigation remains to be done. Bulk densities in these two units maintained nearly constant values of ~1.7 g/cm3, and porosities clustered between 50% and 63%.
At ~200 mbsf, there is a major change in lithology from pelagic ooze to glauconite-bearing sandy packstone (see "Lithostratigraphy". Major abrupt changes in bulk density and porosity are present at this depth (Fig. F81A). Bulk densities increase to 2.10 g/cm3. Grain densities range from 2.68 to 2.92 g/cm3, and porosities decrease sharply from ~50% to ~12%.
Lithologies in the basement at Site 1137 (219.5-370.2 mbsf) include basalt flows and interbedded fluvial and volcanic sediments (lithologic Unit IV). Bulk density for the basement units approaches 2.52 g/cm3, close to the mean grain density of 2.78 g/cm3, and the mean porosity is 16.8%.
The general trend exhibited by the index properties data at Site 1137 reflect downhole variations in lithology. In particular, carbonate contents of sediment vary from 50 wt% CaCO3 in Unit I (foraminifer-bearing diatom ooze) to ~90 wt% CaCO3 in Unit II (nannofossil ooze) and most of Unit III (sandy packstone), to as low as 3 wt% CaCO3 (near a depth of 219 mbsf) at the base of Unit III (see "Lithostratigraphy").
Bulk density was measured by the GRAPE every 4 cm on whole sections of cores. GRAPE data are most reliable in full-sized RCB cores and offer the potential for direct correlation with downhole bulk density of discrete samples (Fig. F83A). In pelagic ooze (Units I and II), GRAPE densities correspond well with wet bulk densities determined from discrete samples and logging data. Below ~220 mbsf, basalt and interbedded sediments exhibit much higher bulk densities than overlying sediments. The downhole bulk density profile, bulk density data obtained from discrete samples, and logging values generally correlate, except that logging and discrete sample data for the basement units consistently show higher values than the GRAPE density data. The GRAPE sensor is calibrated with a filled core liner. The larger scatter in the GRAPE bulk density data for the basement units results from the empty space between pieces of core and the fractured nature and narrow diameters of the cores, which, consequently, do not fill the core liner. As expected, the smaller diameter of the RCB cores results in lower bulk density values than if the core liner is filled. Best-fitting results of the logging and GRAPE density data yield a rather good fit between the two data sets, after removing spurious data points from the GRAPE density profile (for details, see "Downhole Measurements").
We measured NGR every 12 cm on unsplit sections of cores from Site 1137. Gamma-ray values are fairly constant in Units I and II (Fig. F83C). NGR count increases distinctly at a depth of ~200 mbsf, corresponding to the boundary between Units II and III. In lava flows of the basement units, the count increases to an average value of 15 cps. Between ~285 and 320 mbsf, within basement, gamma-ray values reached an average high value of more than 55 cps, corresponding to the volcanic siltstone, sandstone, and conglomerate in basement Units 5 and 6 (see "Lithostratigraphy"). The highest count (more than 70 cps) is present in the crystal-vitric tuff (basement Unit 9) between a depth of 344.0-360.7 mbsf. The downhole spectral gamma-ray logging data (see "Downhole Measurements") reveals fluctuations similar to those of downhole NGR profile, corroborating the shipboard measurements.
We determined magnetic susceptibility on all cores from Site 1137. In general, magnetic susceptibility values within the basement units are much higher than those in the sedimentary sections. Specifically, susceptibility values were higher in the flow tops of basement Units 7, 8, and 10. More detailed results are discussed in "Paleomagnetism".
We determined compressional wave velocity (Vp) of discrete samples using the contact probe system (PWS3). The compressional wave velocity data for Units I and II, which consist of foraminifer-bearing diatom and nannofossil ooze, respectively, show very little scatter, with a mean value of 1656 m/s (Table T17; Fig. F81). CaCO3 contents are consistently high in Units I and II (see "Lithostratigraphy"). The velocities for Units I and II should be lower than in situ velocities because soft sediments are disturbed when drilled by RCB. A notable velocity contrast at a depth of ~200 mbsf marks the boundary between Units II and III. Compressional wave velocity in Unit III increase abruptly from 1939 to 4342 m/s. These changes correspond to a decrease in porosity from 57% to 12%. Within the basement units, velocities typically exceed 3000 m/s (Figs. F81D, F82E); the highest velocity is 6565 m/s. Velocities within basement Units 7, 8, and 10 correlate with the degree of alteration estimated from visual inspection (see "Alteration and Weathering"). The least-altered samples have velocities greater than the most, and flow tops that are highly altered and brecciated.
Logging in Hole 1137A yielded good quality velocity data that can be used to compare with velocity results from physical properties measurements. Because the PWS3 technique does not allow velocity determination at in situ temperature-pressure conditions, velocity values from the sonic log should be higher than shipboard laboratory values. However, we obtained similar velocity values from the two techniques for sediments within Units I and II (Fig. F81). We think this agreement is coincidental because low ultrasonic velocities result from core disturbance, and lower sonic velocity values are caused by an enlarged borehole in Units I and II during logging (see discussion in "Results"). Within the basement units, discrete velocity results agree well with the sonic log data. However, within the basement Unit 6 (~300 mbsf) the discrete velocity values are much more scattered (Figs. F81D, F82E). This discrepancy is caused by the large size of clasts in the conglomerate (>3 cm), which prevents representative discrete sampling of this unit for shipboard physical properties measurements. The good agreement between logging and shipboard results at Hole 1137A provides a valuable tool for cross-checking core depths in those sections where core recovery was not 100%. For example, a log-derived compressional wave velocity increase is ~9 m lower than the curated core depth for Core 183-1137A-24R (219.4 mbsf) (Fig. F82E), suggesting that the correct depth for this core should be shifted ~9 m downward (see more discussion in "Downhole Measurements"). The highest velocities (~6000 m/s) in the lowermost massive basalt (basement Unit 10B) seem high and could be influenced by the calibration method, but relatively the trend is correct (see "Physical Properties" in the "Explanatory Notes" chapter).
We determined thermal conductivities for sediment cores and basement rocks, although we could not determine thermal conductivity in the sandy packstone (Unit III) (Fig. F84; Table T18). Thermal conductivity, physical properties, and lithology are strongly related. Thermal conductivity values for sediments from Units I and II are commonly between 1.0 and 1.2 W/(m·K), with a mean value of 1.1 W/(m·K). For the basement units, thermal conductivity values are generally >1.2 W/(m·K), but <2.0 W/(m·K), with a mean value of 1.5 W/(m·K).
At Site 1137, we observed more scatter of grain densities in the nannofossil ooze units than in Site 1135 and Site 1136 oozes. Radiolarians in the Site 1137 can partially account for the scatter, but further studies are needed to investigate other possibilities. Trends in index properties and MST measurements, coupled with changes in compressional wave velocity and thermal conductivity, compare well with the lithologic units and logging data for Hole 1137A. Velocities within basement Units 7, 8, and 10 also strongly correlate with the degree of alteration estimated from visual inspection. The least-altered samples have velocities greater than the highly altered flow tops.