At Site 1144, 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 184-1144A-6H-7, 184-1144B-23X-1, and 184-1144C-21H-9. Sampling intervals were 4 cm for Hole 1144A from the top of the hole down to Section 184-1144A-6H-7 and 8 cm for the rest of Hole 1144A and Holes 1144B and 1144C. The P-wave logger (PWL) data were bad as a result of instrument problems and/or cracks or a void in the sediment cores. Two thermal conductivity measurements per core down to Core 184-1144A-12H and one per core for the remaining cores were also performed on whole-round sections. Color spectral reflectance was measured on the archive halves of all split cores at 4-cm sampling intervals. Moisture, density, and P-wave velocity (using the P-wave velocity sensor 3 [PWS3]) 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 PWS3 could not detect the ultrasonic signals below Section 184-1144A-5H-1 because of core disturbance associated with gas expansion. Therefore, the P-wave velocity values are not presented here.
Results from core logging with the MST reveal three characteristic intervals. The first interval (0-100 mcd) is defined by a trend of steadily increasing GRA density and NGR (Figs. F24, F25). This trend is related to the compaction in the top of the sediment column, at least for the GRA and probably also for the NGR because the intensity counted is density dependent. Superposed on this first-order trend are smaller but well-defined fluctuations. Rather surprisingly, MS—which often shows patterns similar to the NGR—does not follow this trend (Fig. F26). Instead, the MS signal is low (~20 × 10-5 SI) and flat except for a distinct depression at 8-18 mcd.
The second interval (100-420 mcd) is defined by a trend of a markedly decreased rate of downhole increase in GRA and NGR compared to the first interval. The superposed variations in these signals are of relatively large amplitude (Figs. F24, F25). The MS continues the rather featureless and low-amplitude downhole trend that it exhibits in the upper interval, except for some spikes associated with ash layers (Fig. F26; see "Lithostratigraphy").
The third interval is defined by a very distinct increase in MS, GRA, and NGR at 420 mcd (Figs. F24, F25, F26). Overall, this transition is the most conspicuous feature in the core logs. The MS values increase abruptly from ~20 × 10-5 SI to 60 × 10-5 SI, then increase further to 120 × 10-5 SI. This indicates a major change in supply or, less likely, in the chemical or biogenic production of magnetic minerals. The GRA values increase from ~1.7 to >1.8 g/cm3 over this transition and suggest a markedly reduced porosity and/or a significant change to a higher density mineralogy.
Bulk density estimates from GRA and from moisture and density (MAD) measurements show a generally good agreement in the lower part of the hole and significant offset in the upper part (Figs. F24, F27). The great scatter in GRA data, which are biased toward underestimating the true values, decreases downhole, and so does the discrepancy between GRA and MAD bulk density estimates (Figs. F24, F27). Figure F27 demonstrates that the discrepancy is much more severe for lower density values in general and for APC cores in particular. This phenomenon can be attributed to core disturbance by gas expansion (observed directly when cutting the cores into sections) and indirectly from the numerous voids created in the cores by the pressure of the escaping gas.
Grain density values vary between 2.60 and 2.75 g/cm3 and show a generally increasing downhole trend (Fig. F28), suggesting an increase in carbonate (see Fig. F19; "Organic Geochemistry"). This trend is disrupted by significant excursions (~0.5 g/cm3) at 70-120 mcd, 120-150 mcd, 280-320 mcd, and 320-360 mcd. Porosity reveals a steep decrease from 80% to 65% in the uppermost interval (0-100 mcd), compatible with the increase in bulk density from 1.35 to 1.65 g/cm3 (Figs. F24, F28) and indicating a strong downhole compaction of the sediments over that interval. In the middle interval (100-420 mcd), porosity decreases further at a lower rate from 65% to 55%. At 420 mcd, porosity abruptly decreases to 50%. This lowermost interval corresponds to the abruptly increased MS values (Fig. F26). Postcruise studies will determine if this abrupt transition is strictly a change in mineralogy and lithology affecting porosity and density or (less likely) if it is a hiatus or fault that brings into contact strata with different compaction histories.
The transition from APC to XCB coring (260.15 mcd in Hole 1144A; 219.54 mcd in Hole 1144B), which had a severe effect on the data from Site 1143, has only a minor effect here. This is probably less because of better XCB core quality than because of severe gas expansion that affected APC and XCB cores alike to a depth of ~350 mcd.
Neither the PWL sensors on whole cores nor the PWS3 measurements of P-wave velocity from split-core sections yielded useful results because of abundant voids and cracks from gas expansion.
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. F29). Although L* can generally be used as a first-order approximation of the relative concentration of carbonate, the relationship between L* and shipboard carbonate measurements is not apparent, perhaps because of the low carbonate sampling resolution. A general correspondence with the three intervals defined by the MST core-logging data is recognizable. Most of the uppermost interval (18-100 mcd) is characterized by an increase in L* from 33% to 40%; the uppermost 18 m shows the opposite trend. The middle interval (100-420 mcd) denotes a very gentle general increase from 40% to 44%, with larger fluctuations (~5%) superimposed on the general trend. The lowermost interval below 420 mcd (but only to 500 mcd) reveals a decrease from 44% to 40%. The trends of the a*/b* ratio, a proxy for color change that can be related to a combination of carbonate or organic matter content, clay mineralogy, oxidation, and so forth, are quite different. From 0 to 150 mcd, the parameter has a constant value around 0 with few excursions. Below that interval, high frequency and amplitude variations between 0 and -1.5 are observed and may indicate a color bedding, perhaps the green clay layers. Postcruise spectral analysis will be required to interpret these records.
Thermal conductivity values increase downhole from 0.9 to 1.1 (W/[m·K]) (Table T15, also in ASCII format; Fig. F30). The low sampling resolution reveals one more abrupt increase near 420 mcd, suggesting that the generally positive correlation between thermal conductivity and bulk density is valid here too.
Four downhole temperature measurements with the APC temperature tool were taken in Hole 1144A at depths of 25.9, 54.4, 101.9, and 149.4 mbsf, respectively. In addition, a bottom-water temperature measurement was taken before coring in Hole 1144B (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. Measurements at 25.9 mbsf seem problematic. The estimated errors in equilibrium temperature vary from 0.2° to 0.5°C, reflecting the amount of frictional heat introduced during the 10-min measurement as a result of heave. Depth errors are on the order of ±0.5 m. The measurements between 0 and 149.4 mbsf yielded a thermal gradient of 24°C/km (Fig. F32), which is less than one-third of the thermal gradient observed in Hole 1143A.