Physical properties evaluation at Site 1118 included nondestructive measurements of bulk density, bulk magnetic susceptibility, natural gamma ray, and P-wave velocity on unsplit cores using the MST. Discrete measurements of longitudinal and transverse P-wave velocities and index properties were collected on split cores. Because of the semi-indurated to well-lithified nature of the recovered sediment, thermal conductivity was measured solely from discrete rock samples. Neither undrained shear strength nor unconfined compressive strength were measured at Site 1118 because the level of sediment consolidation was too high.
Bulk densities at Site 1118 were derived from both gamma-ray attenuation porosity evaluator (GRAPE) measurements conducted on unsplit cores and discrete mass and volume measurements (Table T13; also in ASCII format). A full compilation of NGR values is presented with the MST measurement data set in ASCII format (see "Related Leg Data"). Composite profiles of these independently derived bulk densities indicate a similar trend in the two data sets with the discrete measurements defining an upper boundary of the GRAPE densities (Fig. F64). As observed at earlier Leg 180 sites (e.g., "Site 1115" chapter), GRAPE underestimation of bulk density is most likely related to small core diameters, a ramification of the RCB-coring method. Because of the high magnitude of scatter in the GRAPE data, our discussion will focus on the discrete bulk density profile.
Bulk densities at Site 1118 remain approximately constant for most of the borehole (Fig. F64). From the onset of significant core recovery at ~250 mbsf and extending to a depth of ~410 mbsf, bulk densities are characterized by minor scatter and average ~1.8 g·cm-3. Between ~410 and 440 mbsf, the bulk densities exhibit a marked offset, averaging 1.9 g·cm-3. This is observed within the claystones, siltstones, and sandstones of lithostratigraphic Unit II. Below 440 mbsf, the bulk densities remain fairly constant, ranging between 1.8 and 2.0 g·cm-3 until 670 mbsf. At 670 mbsf, bulk density decreases to less than 1.8 g·cm-3, which corresponds to the transition from lithostratigraphic Unit III to Unit IV. Following this decrease, the densities within lithostratigraphic Unit IV increase slightly with depth, reaching a value of 1.9 g·cm-3 at 812 mbsf. Within the top of Unit V, from 812 to 833 mbsf, bulk densities average 1.9 g·cm-3. In the lower interval of Unit V, however, the bulk densities increase significantly from 1.9 g·cm-3 at 833 mbsf to >2.0 g·cm-3 at 845 mbsf. From 845 to 862 mbsf, spanning the packstones of Unit VI and the paraconglomerates of Unit VII, densities further increase to 2.4 g·cm-3. High bulk densities (2.8-2.9 g·cm-3) at the base of the borehole correlate to the dolerite of lithostratigraphic Unit VIII. Bulk density outliers within the sedimentary units of the succession (i.e., 433, 503, and 767 mbsf) cannot be explained geologically and, instead, are likely a result of experimental or instrument-related error.
The profile of Site 1118 grain densities indicates a linear decrease in density with depth (Fig. F65A). Exceptions are found at ~440 mbsf, where a slight offset to lower grain densities is observed, and between 620 and 640 mbsf and 833 and 862 mbsf, where densities locally increase from ~2.6 to >2.7 g·cm-3. A minor increase in the magnitude of scatter is seen in lithostratigraphic Unit III, which may be related to the degree of sandstone and siltstone interbedding within these sediments. As with the bulk density outliers, the peak grain density values at 433, 503, and 767 mbsf most likely reflect experimental or instrument-related error. High grain densities of 2.9 g·cm-3 at the base of the succession are derived from the dolerite of lithostratigraphic Unit VIII.
Porosity-depth relationships are often a function of loading history and lithostratigraphic variations. At Site 1118, a combination of these factors may be responsible for the relatively high porosities observed throughout the depth profile (Fig. F65B). From the onset of coring at 205 mbsf, porosities within the sedimentary succession decrease gradually with depth, but exhibit a lower boundary of only 40%. For homogeneous sediments that are not overpressured, porosity loss typically follows an exponential relationship (e.g., Terzaghi, 1925; Athy, 1930). The porosities in the upper depths (<380 mbsf) of Site 1118 thus fall within an expected range. In contrast, the porosities observed at greater depths (i.e., 380-670 mbsf) decrease only slightly and are unusually high. Such a profile may reflect underconsolidation over this depth range, possibly induced by high sedimentation rates (435 and 485 m/m.y; highlighted zones in Fig. F65B). A sharp increase to porosities >50% is observed beginning at ~670 mbsf, after which the porosities gradually decrease but remain >40% to a depth of 850 mbsf. This abrupt increase corresponds to a thick, moderately calcareous sand unit (see "Downhole Measurements") and the transition into coarse, volcaniclastic sands (see "Lithostratigraphic Unit IV"). The higher porosities in the 670-850 mbsf interval may, therefore, be a function of both lithostratigraphic change and a high sedimentation rate (485 m/m.y.). At the base of the borehole, porosities decrease from ~35% at 850 mbsf to <5% at 899 mbsf, reflecting the transition from packstones and paraconglomerates (lithostratigraphic Units VI and VII, respectively) to dolerite conglomerate (lithostratigraphic Unit VIII).
Compressional wave, or P-wave, velocity was measured on split cores using the PWS3 contact probe system. All cores were sufficiently indurated for ~10-cm3 sample cubes to be prepared, thereby allowing for velocity measurement in the transverse (x and y) and longitudinal (z) directions. The velocity data are presented in Figure F66 and Table T14 (also in ASCII format).
Both transverse and longitudinal velocities show a generally linear relationship with depth with some smaller scale variations (Fig. F66). Superposed logging velocities on the longitudinal (z) velocity show reasonable agreement. In addition, the logging velocities provide information about the uncored interval. The logging data indicate a slight increase in velocities upsection between 210 and 260 mbsf and show a trend above ~210 mbsf that differs from that defined for ~260 to ~800 mbsf within the cored interval (see "Downhole Measurements").
Between 260 and ~450 mbsf, velocities range between ~1650 and 2000 m·s-1. A slight but abrupt decrease in both transverse and longitudinal velocities is found at ~660-670 mbsf, corresponding with the transition from lithostratigraphic Units III to IV. Lithostratigraphic Unit IV is a silty claystone/clayey siltstone interbedded with coarse-grained volcaniclastic sands and is consistent with the logging data interpretation that defined a relatively thick sand layer between 693 and 736 mbsf (see "Log Unit L8"). Velocities increase rapidly across the transition defined by lithostratigraphic Units V and VI; lithostratigraphic Unit V is characterized by variably interbedded, poorly sorted mixed sandy and silty claystones, siltstones, and cemented sandstones with coarse-grained sandstones rich in bioclasts toward the base of the unit. Lithostratigraphic Unit VI is a shallow-water limestone (see "Lithostratigraphic Unit VI"). Velocities continue to increase through lithostratigraphic Unit VII, exceeding 5000 m·s-1 in the dolerite at the base of the borehole. In general, neither the linear increase of velocity with depth nor the observed minor variations (e.g., at ~540 and ~660-670 mbsf) appear to be related to variations in carbonate content (see "CaCO3, Sulfur, Organic Carbon, and Nitrogen").
Although there is a considerable amount of scatter within the anisotropy data (Fig. F67), transverse and longitudinal velocities typically vary by less than ± 10%. From 220 to 280 mbsf, anisotropy is positive, which indicates that the transverse velocities are greater than longitudinal velocities. In contrast, longitudinal velocities generally exceed the transverse velocities between 280 and 380 mbsf. From 380 to 900 mbsf, the anisotropies are consistently skewed by ~5% toward higher transverse velocities. There is no obvious explanation for the positive-negative change in anisotropy at ~280 mbsf.
Thermal conductivity data were obtained as a series of two to four repeat measurements per interval (i.e., discrete samples) and are reported in Table T15 (also in ASCII format). Thermal conductivity data with depth are presented as mean averages of the repeat measurements shown in Figure F68.
Above 280 mbsf, thermal conductivities exhibit some scatter with values ranging from 1.00 to ~1.30 W·m-1·°C-1 (Fig. F68). Between 280 and 520 mbsf, thermal conductivity values increase slightly from ~1.00 W·m-1·°C-1 to ~1.25 W·m-1·°C-1. Within lithostratigraphic Unit III, values range between 1.15 and 1.20 W·m-1·°C-1 and remain fairly constant with depth. At 680 mbsf, the thermal conductivities are characterized by an offset, whereby the values decrease from ~1.80 to <1.00 W·m-1·°C-1. From 680 to 850 mbsf, spanning the claystones and siltstones of Units IV and V (see "Lithostratigraphic Unit IV" and "Lithostratigraphic Unit V"), conductivities increase to 1.40 W·m-1·°C-1. The lowermost rocks recovered from Site 1118 constituting packstones, grainstones, and dolerite, are thermally more conductive with values ranging between ~1.50 and 2.00 W·m-1·°C-1.
At Site 1118, estimates of magnetic susceptibility readings were routinely obtained as part of the MST measurement. The quality of magnetic susceptibility data is often poor in RCB-cored boreholes such as Site 1118, commonly because of a combination of reduced core diameter and core fracturing. The full magnetic susceptibility measurement data set can be found as part of the MST compilation in ASCII format on the accompanying LDEO CD-ROM.
The magnetic susceptibility of the recovered section is displayed in Figure F69A and is compared with the remanent magnetic intensity (Fig. F69B). A general correlation exists for the first-order variation in magnetic susceptibility and remanent magnetic intensity. This correlation implies that, in general, the mineralogy controlling the magnetic susceptibility is the same as that controlling the remanent magnetic intensity. At the grain-size scale and, thus, the distribution of sandstones and siltstones, there is no consistent relationship among magnetic susceptibility, remanent magnetic intensity, and grain size (see "Lithostratigraphy"). The compressed scale of Figure F69 allows only the general trends in the magnetic susceptibility to be identified. In particular, there exists a first-order difference between the high-amplitude susceptibility observed within the upper part of the section (240-580 mbsf) and the low-amplitude susceptibility within the lower part of the section (580-840 mbsf). The transition is found within lithostratigraphic Unit III. Second-order trends are represented by the relatively high amplitude susceptibility variations present at the base of lithostratigraphic Unit V and the transition between the packstones and grainstones of lithostratigraphic Unit VI and the paraconglomerates of lithostratigraphic Unit VII (~860 mbsf). Numerous local maxima were observed, the more prominent at 390, 410, 520, and 640 mbsf. With the exception of lithostratigraphic Units VI and VII, there is no clear relationship between lithology and magnetic susceptibility. Further, sedimentation rates determined from biostratigraphy (see "Sediment Accumulation Rate") exceed 400 m/m.y. for the stratigraphic succession spanning the first-order change in susceptibility. Therefore, we conclude that no obvious relationship exists between sedimentation rate and the variations in magnetic susceptibility.
Natural gamma ray (NGR) emissions were recorded on cores from Site 1118 as part of the continuous MST measurements. The corresponding emission count is plotted in Figure F70B with magnetic susceptibility (Fig. F70A) for comparison. Superposed on the NGR count is the total gamma-ray (HSGR) logging data. The agreement between the MST gamma-ray data and the logging gamma-ray data provides confidence in using the logging curves in regions of poor core recovery. A full compilation of NGR values is presented with the MST measurement data set in ASCII format on the accompanying LDEO CD-ROM.
Apart from a relative low NGR count between 240 and 285 mbsf and 860 and 880 mbsf, NGR is rather uniform down the borehole with values generally ranging between 15 and 30 c/s. Between 240 and 530 mbsf, there exist a number of small undulations in the NGR count. Local maxima are found at 310, 350, 400, 475, and 850 mbsf. Below ~530 mbsf, the NGR count remains essentially constant down to a depth of ~840 mbsf (Fig. F70B). No obvious relationship exists with the majority of the succession, although it might be reasonable to interpret the high-frequency variation in NGR count observed in both the MST and logging data to be a function of the continuous sequence of alternating sands and silty clays of lithostratigraphic Units I, II, III, and IV (see "Lithostratigraphy"). It is interesting to note that lithostratigraphic Unit IV, characterized by coarse-grained volcaniclastic sands, has no obvious response in the NGR count. The shallow-water packstones and grainstones of lithostratigraphic Unit VI (see "Lithostratigraphic Unit VI") correspond to a local maximum in the NGR count. Toward the base of the borehole, the NGR counts drop to nearly zero within the dolerite conglomerates of Unit VIII.