At Site 1114 one borehole was advanced to a total depth of 352.8 mbsf, with a cumulative recovery of 12.4%. Physical properties evaluation at the site included nondestructive measurements of bulk density, bulk magnetic susceptibility, natural gamma ray, and P-wave velocity on unsplit core using the MST. Discrete measurements of longitudinal and transverse P-wave velocities and index properties were collected on split cores. Depending on the level of sediment induration, thermal conductivity was measured from either unconsolidated whole cores or discrete rock slices. Poor recovery and fragmented cores at the top (Core 180-1114A-1R), middle (Cores 16R through 19R), and at the base of the borehole (Cores 33R through 37R) precluded use of the MST for continuous measurements at these locations. Measurements of compressive strength and undrained shear strength were also restricted because of a high level of lithification from Core 180-1114A-2R to the bottom of the succession.
Bulk densities at Site 1114 were derived from both GRAPE measurements conducted on unsplit cores and discrete density measurements on sediment and rock samples (Table T12 and in ASCII format in the TABLES directory). A full compilation of gamma-ray attenuation porosity evaluator (GRAPE) data (in ASCII format) is presented with the MST measurement data set on the accompanying Lamont-Doherty Earth Observatory (LDEO) CD-ROM. Composite profiles of these independently derived bulk densities indicate a fair agreement between the two, with the discrete measurements correlating to the upper boundary of the GRAPE densities (Fig. F45). However, because of the high magnitude of scatter in the GRAPE data, our discussion will focus primarily on the discrete bulk density profile.
Bulk densities change abruptly from ~1.60 g·cm-3 at ~7 mbsf to >2.00 g·cm-3 at ~17 mbsf (Fig. F46A). This discontinuity in the density profile likely reflects an erosional unconformity that resulted in high sediment bulk densities at shallow depths (see "Biostratigraphy" and "Lithostratigraphy"). Below the discontinuity bulk densities remain fairly constant to a depth of 55 mbsf, ranging only between 1.95 and 2.05 g·cm-3. This depth range corresponds to the siltstones and claystones of lithostratigraphic Unit II. Between 60 and 90 mbsf, the bulk densities are also characterized by little scatter and average ~2.05 g·cm-3. This interval corresponds to litho-stratigraphic Unit III, which comprises sandstones, siltstones, and claystones. At 90 mbsf, the bulk densities abruptly increase from 2.00 to greater than 2.20 g·cm-3 and remain between 2.10 and 2.20 g·cm-3 to 120 mbsf. The increase does not correspond to a change in lithology or a unit boundary, and, unfortunately, poor core recovery hinders an interpretation of the density change. From 120 to 140 mbsf, the bulk densities show another increase with values ranging between 2.20 and 2.40 g·cm-3. These measurements may reflect the carbonate-rich intervals within lithostratigraphic Subunit IIIA.
Below a region of no recovery (140-180 mbsf), the bulk densities average ~2.30 g·cm-3 from 180 to 190 mbsf, reflecting the thin conglomerate and coarse sandstone of lithostratigraphic Subunit IIIB. Below 190 mbsf, the bulk densities average ~2.10 g·cm-3 before increasing to nearly 2.40 g·cm-3 at 240 mbsf. This trend in density corresponds to a lithostratigraphic change from siltstones, sandstones, and claystones to a sandstone containing sulfides and smectite (Core 180-1114A-26R; see "Lithostratigraphy"). The presence of these minerals may be conducive to the observed higher bulk density. Below 275 mbsf to the base of the borehole, bulk densities increase from <2.10 to >2.60 g·cm-3. The abrupt increase correlates with the change in lithology from silty claystone (lithostratigraphic Unit V) to tectonic breccia (lithostratigraphic Unit VI) and metadolerite (lithostratigraphic Unit VII).
Grain density data were derived from the same discrete samples from which bulk densities were measured. Grain densities average ~2.70 g·cm-3 from the seafloor to 240 mbsf (Fig. F46B). However, slightly higher densities at 75 and 135 mbsf may be representative of noted carbonate input (see "Organic Geochemistry" and "Lithostratigraphy") and the high at 180 mbsf corresponds to the presence of carbonate-cemented conglomerates. Deviation in the grain density begins ~270-280 mbsf, where low grain densities reflect the presence of silty claystone. Below 290 mbsf, grain densities of the tectonic breccia (lithostratigraphic Unit VI) and metadolerite (lithostratigraphic Unit VII) increase to nearly 3.0 g·cm-3.
The porosity profile strongly reflects bulk density variations, as expected from the measurement method (see "Physical Properties" in the "Explanatory Notes" chapter). At Site 1114, porosities average ~41% from 18 to 56 mbsf and then generally decrease to an average of 22% from 56 to 133 mbsf. Below 180 mbsf, porosity averages 26%. Deeper than 260 mbsf, porosities increase to an average of 42% before abruptly decreasing to ~9% (Fig. F46C). The porosity minima correlate to distinct lithostratigraphic units, with the lows from 120 to 130 mbsf and 275 to 353 mbsf corresponding to the carbonate-cemented sandstones and siltstones of lithostratigraphic Subunit IIIA and the tectonic breccia and dolerite at the base of the succession, respectively.
Surprisingly, the values throughout the entire porosity profile are low, as illustrated by seafloor and near-seafloor values of 65% and 58%, respectively, and an average porosity of 41% even in the shallow depth range of 17-56 mbsf. Low porosities toward the base of the profile are understandable and are likely the result of extended compaction and burial. The anomalous seafloor porosities may reflect an environment in which sediment deposited on the top of Moresby Seamount has been removed. More difficult to interpret, however, is the abrupt decrease in porosity from near-seafloor values of 58%-40% at 17 mbsf. As discussed in the bulk density section, this discontinuity is likely representative of an unconformity within the upper 10 m of the succession. To investigate this hypothesis further, it must first be noted that even though the porosity profile is comprised of values lower than those seen in earlier Leg 180 boreholes, the structure of the profile below 17 mbsf is generally consistent with a negative exponential variation often seen in normally compacting sediments (Athy, 1930). Fitting a least-squares curve to the porosity profile supports the presence of an unconformity because the relationship between depth and porosity in the deeper sediments of the succession is not consistent with the surface porosity (Fig. F47A). Moreover, sediment erosion is consistent with (1) the absence of the upper part of micropaleontologic Zone N21 and Subzones NN19E-F within the upper 10 m of the borehole, which indicates a hiatus in the sedimentary record between at least 0.46 and 1.25 Ma (see "Biostratigraphy") and (2) the interpretation of reflection seismic data suggesting the truncation of reflectors (see "Miocene-Quaternary Arc and Forearc" in the "Background and Regional Setting" chapter). To estimate the thickness of sediment that may have been eroded, a least-squares exponential curve was fit to a porosity profile that included only the data between 17 mbsf and the transition into metamorphic rock (Fig. F47B). The curve fitting predicts an initial porosity of 42.4% and a compaction decay constant of 0.0026 m-1. Extrapolating this porosity-depth relationship to the surface, assuming initial porosities between 65% (i.e., seafloor porosity values from Site 1114) and 75% (i.e., seafloor porosities from other Leg 180 sites), implies that as much as 220 m of sediment has been removed from the upper stratigraphic units at the site. As this estimate is derived from a sparse data set, further analysis was conducted with the density-porosity logging data set (see "Downhole Measurements"). Superposing index properties porosities onto the logging data, removing washout zones, and extrapolating the porosity depth relationship to the surface indicates that more than 400 m of sediment may have been eroded from Site 1114 (Fig. F47C).
Compressional wave, or P-wave, velocity was measured on whole cores using the MST P-wave logger (PWL). On split cores, the PWS3 contact probe system was used to measure velocities. In Cores 180-1114A-1R and 2R, only transverse velocities were measured with the split core remaining in the core liner. From Core 180-1114A-3R to the bottom of the borehole, the level of induration was sufficient for ~10-cm3 cubes to be cut from the cores, thereby allowing for velocity measurement in the transverse (x and y) and longitudinal (z) directions. Discontinuous and fractured cores yielded poor-quality PWL results, and thus this discussion will be limited to PWS velocity data.The PWS data can be found in Table T13 and in ASCII format in the TABLES directory.
Velocities obtained in the upper 100 m of the borehole range from ~1700 to ~2600 m·s-1, which are slightly higher values than expected for shallow-marine sediments. However, higher velocities correspond to the low porosity values observed in shallow sediments at this site and may also reflect the influence of recent erosion, as discussed in "Density and Porosity" and "Depositional History." The x, y, and z velocities from below the seafloor to 100 mbsf all show a fairly linear increase with depth (Fig. F48). Between 120 and 130 mbsf, the linear trend is disrupted by a point spike to nearly 4000 m·s-1, after which the velocities return to values less than 3000 m·s-1. This abrupt increase coincides with lithostratigraphic Subunit IIIA, which is comprised of carbonate-cemented siltstones and sandstones as well as packstones. Below 180 mbsf within lithostratigraphic Units III, IV, and V, the triaxial velocities remained relatively constant, ~2500 m·s-1. In the lower 60 m of the borehole, the velocities increase to between 4300 and 6600 m·s-1 within the tectonic breccia and metadolerite of lithostratigraphic Units VI and VII, respectively.
Further evaluation of the triaxial velocity measurements indicates that transverse velocities are faster than longitudinal velocities when velocities remain below 2600 m·s-1 (Fig. F49A). On the contrary, longitudinal velocities are faster than transverse velocities in a velocity range of 3200 to 6600 m·s-1. Such a trend suggests that transverse velocities generally dominate in the sandstones, siltstones, and claystones, whereas the longitudinal velocities dominate in the calcite-cemented unit and the low-porosity metamorphic units. Maximum velocity anisotropies range from 5% to 8% (Fig. F49B). A reversal in the aniso-tropy occurs at 90 mbsf, where the anisotropy changes abruptly from 4.6% to -1.3%, thereby indicating faster transverse velocities compared with longitudinal velocities. The depth of the reversal is slightly below the first documentation of shear deformation in the sediment section (56 mbsf) and corresponds to an interval characterized by high bedding dip (see "Structural Geology").
Thermal conductivity measurements were conducted primarily on split cores from Site 1114. The needle method was used only on the first core and the half-space method was used thereafter. The thermal conductivity values presented in Figure F50 are averages of repeat measurements in the same interval. A full compilation of the data is presented in Table T14 and in ASCII format in the TABLES directory.
Thermal conductivity values are governed primarily by pore space, and thus the thermal conductivity profile (Fig. F50) parallels that of the porosity (Fig. F46C). The abrupt change in thermal conductivity from the seafloor value of 0.7-1.2 W·m-1·°C-1 at 17 mbsf reflects a stratigraphic hiatus occurring within the upper 10 m of the borehole. Below the unconformity, the thermal conductivity values remain >1.0 W·m-1·°C-1, probably being a function of the unusually low porosities noted in the porosity-depth profile. On average, the thermal conductivity values increase slightly with depth, with values ranging from <1.2 W·m-1·°C-1 to an average of 1.4 W·m-1·°C-1. Two isolated thermal conductivity highs, 1.6 W·m-1·°C-1 at 123 mbsf and 1.8 W·m-1·°C-1 at 324 mbsf, correspond to calcareous siltstone (lithostratigraphic Subunit IIIA) and metadolerite (lithostratigraphic Unit VII), respectively.
At Site 1114 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 1114, commonly because of a reduced core diameter and a propensity for fracturing that usually accompanies RCB-coring methods. The low recovery throughout the succession at Site 1114 also limits the degree of interpretation that can be placed on the magnetic susceptibility data. The full data set can be found as part of the MST compilation (in ASCII format) on the accompanying LDEO CD-ROM.
The magnetic susceptibility data comprise three segmented profiles separated by zones of poor recovery: 18 to 135 mbsf, 180 to 240 mbsf, and 275 to 300 mbsf (Fig. F51A). Within the first section the average magnetic susceptibility decreases slightly from 5 to 4 × 10-3 SI before increasing to a maximum of 10 × 10-3 SI between 70 and 80 mbsf. Below the susceptibility maximum, the average returns to less than 5 × 10-3 SI before increasing to a final peak average ~6 × 10-3 SI between 120 and 135 mbsf (Fig. F51A). The minimal fluctuation in magnetic susceptibility from 20 to 55 mbsf corresponds to the siltstones and claystones of lithostratigraphic Unit II, whereas the remainder of the profile parallels a unit of interbedded sandstone, siltstone, and claystone. Correlating documented grain size (see the "Core Descriptions" contents list for core images) with the magnetic susceptibility profile indicates that even though the fine to medium sands correspond to the two peaks, both sands and clays can exhibit apparent susceptibility highs and susceptibility lows. This observation agrees with the findings from Sites 1108 and 1109.
From 180 to 240 mbsf, magnetic susceptibility values increase from an average of 2.5 to >6 × 10-3 SI at a depth of 210 mbsf. The susceptibility then generally decreases with depth to <4 × 10-3 SI. This depth interval corresponds to the interbedded siltstones, sandstones, and claystones of Unit III. Correlating grain size to magnetic susceptibility in this interval indicates that, like the 0-140 mbsf interval, both sands and clays exhibit apparent highs, although the susceptibility peaks here correspond to predominantly clay units. Magnetic susceptibility values in the lower section of the borehole decrease from an average of 4 × 10-3 SI to nearly 0, paralleling the transition from silty claystone to tectonic breccia and ultimately to metadolerite.
Natural gamma ray (NGR) emissions were recorded on cores from Site 1114 as part of continuous MST measurements. A full compilation of NGR values is presented with the MST measurement data set (in ASCII format) on the accompanying LDEO CD-ROM.
The NGR data indicate a fairly constant NGR count between 10 and 20 counts/s from the seafloor to 100 mbsf (Fig. F51B). Below this depth interval from 100 to 142 mbsf, the counts abruptly increase to ~30 counts/s. From the typical relationship between radioactive elements and lithology type (i.e., an increasing NGR count with increasing clay content), one might expect this trend to indicate a transition from sandy units to clay-dominated units. Instead, the increase in NGR count corresponds to the transition from the sandstones in lithostratigraphic Unit III to the carbonate-rich sandstones of lithostratigraphic Subunit IIIA. The interpreted interval of lithostratigraphic Unit III and Subunit IIIA was based on low recovery (see "Lithostratigraphy"), and thus it may be argued that the units do not represent data sufficient for a comparison with physical properties NGR values. However, conventional logging data and FMS interpretation effectively supplement the lithostratigraphic interpretation and strongly suggest a continuous succession of alternating sand and silty clays over the entire length of the lithostratigraphic Unit III and Subunit IIIA interval. Further evaluation of grain-size distribution for Unit III and Subunit IIIA (see the "Core Descriptions" contents list) indicates that the increase in NGR count is a function of increasing sand content. This trend suggests the presence of radioactive sands, which is confirmed by increasing uranium, thorium, and potassium observed from 122 to 140 mbsf in the logging data (see "Downhole Measurements").
Below 180 mbsf, NGR values decrease from ~25 counts/s at 180 mbsf to ~12 counts/s between 200 and 220 mbsf. From 220 to 240 mbsf, the gamma-ray count increases to nearly 30 counts/s. The 180 to 240 mbsf depth interval corresponds primarily to lithostratigraphic Unit III, with the sandstone Unit IV spanning the lower 5 m of the interval. Once again, the apparent NGR trend cannot be related to lithostratigraphic changes or unit boundaries, although comparison to grain-size distribution and logging data indicates the presence of radioactive sands at 180 and 240 mbsf. Toward the base of the borehole, the NGR count drops to nearly zero within the metadolerite.
Data from downhole logging fill gaps in physical properties measurements and allow us to assess whether index properties data are representative of the cored section. This is particularly important at Site 1114 where core recovery was only 12.4%. In general, index properties determinations of bulk density are in good agreement with the logging data (Fig. F52). Two exceptions are observed between 120 and 140 mbsf, where index properties bulk density exceeds that from the logging. A feasible explanation is that these samples were from layers that were too thin to be represented by the 40-cm resolution of the density logging tool (RHOM). Logging data below 220 mbsf indicate very low bulk densities, but data quality in this zone may be degraded by washouts located from 223 to 235 mbsf, 241 to 247 mbsf, 277 to 280 mbsf, and 288 to 292 mbsf (see "Downhole Measurements," shaded zones, Fig. F52). Physical properties measurements of longitudinal (z-direction) velocity are generally high relative to data from downhole sonic velocity logs (Fig. F52). The reason for this discrepancy is unclear. One possible explanation relates to the 1-m resolution of the sonic logging tool (DTCO), which could have aliased the response from thin, high-velocity layers. Alternately, the bias may be caused by preferential index properties sampling of higher velocity material, a procedure necessary for supplementing the acoustic impedance contrast calculations.