At Site 1145, physical properties were measured on whole-round sections, split-core sections, and discrete samples from the latter. Whole-core logging with the MST included GRA bulk density, MS, NGR, and P-wave velocity logging on all cores. Sampling intervals were 5 cm for all cores in the three holes. One thermal conductivity measurement per core was also performed on the whole-round sections. 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). 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 report but are available from the ODP JANUS database (see the "Related Leg Data" contents list).
Core physical properties measurements show three major features. The first one is related to the change from APC to XCB coring (136.23 mcd in Hole 1145A, 134.16 mcd in Hole 1145B, and 132.86 mcd in Hole 1145C). The XCB cores are moderately disturbed by partial remolding and incorporation of drilling slurry. The reduced diameter of XCB cores is probably the main component of the slight offset of GRA, MS, and NGR values at those depths (Figs. F17, F18, F19). This effect is not compensated for because there is no time to perform a careful correction on board ship.
The other two primary features in the core-logging data are related to changes in sediment composition. One is the cyclical fluctuations of data from the MST over the entire section (Figs. F17, F18, F19). The other characteristic is an abrupt downhole increase in GRA, MS, and NGR values, accompanied by a decrease in porosity, at 80 mcd (Figs. F17, F18, F19, F20). These increasing downhole trends level out at ~140 mcd. These features are described in the next section.
The GRA, MS, and NGR data show high-amplitude cyclicity over the entire interval recovered (Figs. F17, F18, F19). These cycles are best defined in the NGR data, where the dominant wavelength changes at ~75 mcd from ~10-15 m in the upper interval to ~2-5 m in the lower interval. These fluctuations are interpreted as glacial-interglacial compositional changes. Based on preliminary correlations with oxygen isotope reference curves and chronostratigraphic results (see "Sedimentation and Accumulation Rates"), the change in cyclicity occurs at ~0.4 Ma and is associated with a fourfold increase in sedimentation rate from the lower to the upper interval.
Below the change in dominant wavelength at ~75 mcd, the average values of GRA, MS, and NGR roughly double (Figs. F17, F18, F19). The abrupt increase in these values is accompanied by a sudden decrease in porosity from ~70% to ~55% (Fig. F20). Porosity appears to clearly define an interval of excursion from a linear trend connecting the uppermost 75 mcd with the interval below 170 mcd. The porosity decrease alone cannot account for the changes observed in MS and NGR over the interval from 75 to 170 mcd. We therefore infer a significant change in lithology that also affects porosity and, thus, bulk density. Near 75 mcd, a change in grain density to slightly higher (from ~2.65 to ~2.70 g/cm3) and less variable values is also observed and supports the interpretation of a change in mineralogic composition (Fig. F20). Shore-based analysis of the sediments will reveal the components and sources affecting this change.
At ~133 mcd, GRA bulk density shows a sharp offset caused by the change from APC to XCB coring. This becomes clear when comparing the bulk density data derived from GRA with the more accurate data obtained from the moisture and density (MAD) method, which do not show the offset at that depth (Fig. F17).
The CSR data are presented as records of two parameters from the L*a*b* color system: L*, representing the lightness in percent; and a*/b*, the ratio of the two chromaticity parameters (Fig. F21). L* can be used as a first-order approximation to the relative concentration of carbonate. This correlation is not yet readily apparent because shipboard carbonate measurements were done at a low sampling resolution. There is no major downhole trend in either the carbonate concentrations or L*. Cyclic changes are present throughout the L* record and correlate with those seen in other parameters and interpreted as glacial-interglacial cycles. The a*/b* ratio is a proxy for color change that can be related to a combination of carbonate or organic matter content, clay mineralogy, oxidation, and so forth. A distinct minimum and subsequent inversion is observed at ~88 mcd and can be related to the change in lithology indicated by all other parameters at ~75 mcd.
In the uppermost 58 mcd, P-wave velocity sensor PWS1 and PWS2 values are at ~1520 m/s and show little variability (Fig. F22). Below that depth, values sharply increase and fluctuate between ~1550 and ~1680 m/s (Fig. F22). The abrupt change at 58 mcd is the result of an operational error that produced inaccurate transducer displacement measurements. The higher velocities in the lower interval were therefore overestimated.
Thermal conductivity data from the APC and XCB cores range from 0.85 to 1.15 W/(m·K) (Table T15, also in ASCII format; Fig. F23). The values from XCB cores are compromised by core quality, particularly in the upper XCB interval. The values from APC cores show a relatively linear, downhole increasing trend. A slight increase at ~80 mcd is observed, which corresponds to a downhole gain in bulk density at that depth.
Three downhole temperature measurements with the APC temperature tool were taken in Hole 1145A at depths of 29.9, 58.4, and 96.4 mbsf, respectively. Also, a bottom-water temperature measurement was taken before coring in Hole 1145B (Fig. F24). 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 0.2° to 0.4°C, reflecting the amount of frictional head introduced near the sensors during the 10-min measurements. Depth errors are on the order of ±0.5 m. The measurements between 0 and 96.4 mbsf yielded a thermal gradient of 90°C/km (Fig. F25).