At Site 1148, physical properties were measured on whole-round sections, split-core sections, and discrete samples from the latter. Whole-round core logging with the MST included GRA bulk density, MS, and NGR on all cores as well as P-wave velocity logging from the top of the holes down to Sections 184-1148A-16H-7 and 184-1148B-15H-7. Sampling intervals were 5 cm for all cores in the two holes. The P-wave logger (PWL) data were bad because of instrument problems and/or cracks or voids in the sediment cores. The PWL data are not shown in this text but are available from the ODP JANUS database (see the "Related Leg Data" contents list). One thermal conductivity measurement per core was also performed on Cores 184-1148A-1H through 33X and 184-1148B-1H through 15H as long as sediment conditions allowed. Color spectral reflectance was measured on the archive halves of all split cores at 4-cm intervals. Moisture, density and P-wave velocity were measured on discrete samples from split-core sections at intervals of one measurement per section (1.5 m) (see "Physical Properties" in the "Explanatory Notes chapter").
Similar to the previous sites, one feature in the core-logging data is related to the change from APC to XCB coring (155 mcd in Hole 1148A). The XCB cores are moderately disturbed by partial remolding and incorporation of drilling slurry and have slightly smaller diameters than APC cores. This results in an offset of GRA data and has a very minor effect on the MS and NGR data at this site. The other primary features in the physical properties data can be ascribed to changes in sediment composition. We can distinguish two major sediment units from a sharp and drastic offset of all properties at 477 mcd. In addition, the cored interval at this site can be subdivided into eight intervals characterized by clear but less pronounced changes in some physical properties.
Within the first interval, core-logging data as well as moisture and density (MAD) bulk density increase gently, porosity decreases correspondingly, and grain density shows a large scatter around 2.65 g/cm3 (Figs. F24, F25, F26, F27). Superimposed cyclic fluctuations (which may correspond to glacial-interglacial cycles) in core-logging data have large amplitude and relatively large period (8-10 m). This interval closely resembles the upper interval at Site 1147.
In the second interval, the gradients of the general trends in core-logging and MAD bulk density data are steeper than in the interval above. Cyclic fluctuations are still of high amplitude but with smaller period (~3 m) (Fig. F26).
At the downhole transition to the third interval, the general trend flattens significantly in all data except for the CSR parameters, which increase (L*) and decrease (a*/b*) (Fig. F28). These changes in the long-term trend, as well as the changes over a shorter interval, appear to be controlled by variations in carbonate content. Low carbonate values induce apparent highs in NGR and MS (Figs. F25, F24) and lows in L* reflectance values; high carbonate contents seem to suppress the NGR and MS values (see also "Organic Geochemistry"). The a*/b* ratio clearly distinguishes several smaller intervals that are also visible in the MS, porosity, and grain density records (Figs. F24, F27) and are very often described by a visual color change from brown to green (see "Lithostratigraphy"). The a*/b* ratio displays five major offsets that bound intervals of characteristic color spectral reflectance at 175, 318, 345, 400, and 450 mcd (Fig. F28). The MAD bulk density in this interval steadily increases, reflecting compaction. The GRA values are lower than the discrete MAD values because of XCB coring below 155 mcd. Also, GRA displays some coring-related variations, especially in the upper part of this interval (Fig. F26).
The short fourth interval is marked at the top by a sharp increase in P-wave velocity and L* and a*/b* CSR parameters as well as a drop in porosity (Figs. F27, F28, F29). The MAD bulk density values are distinctively higher within this interval. The bottom is marked even more sharply by a reversal in these physical parameters, which are most likely controlled by the increased carbonate content in this interval (50%-75%; see "Organic Geochemistry"). This interval is probably responsible for the highly reflective sequence at ~4.9 s in the seismic profiles for the site (see "Sites 1147 and 1148 [SCS-5C]" in "Seismic Stratigraphy of Leg 184 South China Sea Sites" in the "Seismic Stratigraphy" chapter).
Core recovery was poor in the fifth interval, and only a few data points are available. However, a drastically lowered grain density as well as reduction in bulk density and P-wave velocity values are significant. All samples from this interval consist of a greenish clay-rich material, which was strongly disturbed by the coring process. Coring disturbance may affect the data for this interval to a certain degree, although the grain density signal is hard to explain.
The sixth interval is characterized by constant values in all data sets. The MS values are very low (Fig. F24). The bottom of this interval is marked by a thin intercalation with increased carbonate content, high P-wave velocities, and high bulk densities.
Within the seventh interval, MS and NGR increase; the NGR record, in particular, displays some higher amplitude fluctuations. P-wave velocity, bulk density, and porosity records show an archlike feature with increasing values from 593 to 642 mcd and a decrease from 642 mcd to 682 mcd (Figs. F26, F27, F29).
This lowermost (eighth) interval is distinguished by high-amplitude variations in NGR, constant MS and GRA, decreasing L*, and an almost constant a*/b* ratio, indicating very low color variability (Figs. F24, F25, F26, F28). Porosity (Fig. F27) and MAD bulk density show some minor variations in Hole 1148A. In the lower part of Hole 1148B, the discrete samples for MAD follow the downward increasing trend already indicated in Hole 1148A (Fig. F27). The P-wave velocities in Hole 1148B (Fig. F29) in the interval from 682 to 850 mcd display constant values until 760 mcd, then rapidly increasing values peak in maximum velocities of 2600 m/s at 792 mcd. Below that narrow horizon, P-wave velocities are lower again at ~2300 m/s and show some more scatter.
Thermal conductivity data from the APC and XCB cores range from 0.85 to 1.30 W/(m·K) (Table T17, also in ASCII format; Fig. F30). The values from XCB cores are compromised by poor core quality, particularly in the upper XCB interval. The general trend follows that of bulk density.
Four downhole temperature measurements with the APC temperature tool were taken in Hole 1148A at depths of 37.3, 68.2, 108.6, and 162.0 mcd, respectively (Fig. F31). The objective was to establish the local heat flow. Original temperature records were analyzed using "Tfit" software to establish the equilibrium temperature at depth. The estimated errors in equilibrium temperature vary from 0.3° to 0.5°C, reflecting the amount of frictional heat introduced by the ship's heave near the sensor during the 10-min measurement. Depth errors are on the order of ±0.5 m. The measurements between 0 and 162 mcd yielded a thermal gradient of 83°C/km (Fig. F32).