Physical property data collected during Leg 208 provided an initial measure of the lithologic variations in the recovered core, revealing both long-term trends and high-frequency oscillations that could be interpreted in terms of the geological history of the drill sites. The information was used to (1) define major lithostratigraphic unit boundaries, (2) correlate cores from multiple holes to construct composite sections and stratigraphic splices, (3) correlate core data with downhole logging data, (4) identify effects due to sediment compaction and coring disturbance, (5) assess the relationships between signal frequencies and orbital forcing, enabling postcruise cyclostratigraphic studies, and (6) investigate the location and characteristics of major seismic reflectors.
All physical property measurements were taken on cores after they had attained room temperature, which took 2–4 hr. MS, GRA bulk density, P-wave velocity, NGR, and electrical conductivity were measured at high resolution on whole cores using the MST. Thermal conductivity was measured on whole cores as well. After the cores were split, additional measurements of P-wave velocity were conducted on the working half, and moisture and density (MAD) measurements were taken on discrete samples to calculate porosity, grain density, and bulk density. The instruments and apparatus used during Leg 208 are discussed in Blum (1997) and are outlined below.
The MST combines five physical property sensors on an automated track that measure bulk density, MS, P-wave velocity (by PWL), NGR, and bulk electrical conductivity on whole-round core sections. These nondestructive measurements were taken after the cores had equilibrated to at least 18°C and before the cores were split. The MST data were sampled at the highest sampling rate possible given the time constraints of coring operations. Most cores were measured at a sample spacing of 2.5 cm, a common denominator of the distances at which the instruments are located on the track. Some intervals had to be measured at 5-cm sample spacing to accelerate core processing. The sampling periods were 4 or 5 s.
The quality of these core data and the accuracy of the nominal values were degraded if the core liner was not completely filled and/or the core was disturbed. However, general downhole trends could still be used for core-to-core and core-to-well logging correlation in most cases.
On every other core section (nominal sampling interval of 3 m) a sound velocity measurement was taken using the P-wave velocity sensor 3 on the Hamilton Frame probe (PWS3). A sediment sample of ~10 cm3 was subsequently extracted from the PWS3 measurement location and subjected to MAD measurements. An additional small core sample was taken from the same location and passed to the chemistry laboratory for the determination of calcium carbonate concentration.
Two instruments are mounted on the AMST for the measurement of color reflectance and MS. Both instruments are moved across the track by stepper motors and landed on the split-core surface at predetermined sampling intervals for the measurements. Freshly split cores were covered with clear plastic wrap before being placed on the AMST to protect the probes from being soiled. The AMST runs a laser scan first to determine surface roughness and to allow the skipping of intervals where the core surface is well below or above the level of the core liner. However, the AMST cannot recognize relatively small cracks or disturbed areas of core. Thus, AMST data may contain spurious measurements that should, to the extent possible, be edited out of the data set before use.
Color reflectance was measured on the archive halves after the cores were described and before they were measured for magnetic intensity, inclination, and declination in the cryogenic magnetometer. Sample spacing was 2.5 cm throughout the leg, except for critical intervals such as the P/E and K/P boundary intervals, which were measured at a spacing of 1 cm.
MS was measured using the "point sensor" on selected intervals. These measurements are very slow with the available equipment; therefore, only the critical intervals were measured. The sample spacing was usually 1 cm for those intervals.
Whole-core MS was measured with a Bartington MS2C meter using an 80-mm internal diameter sensor loop (88-mm coil diameter). The measurements were routinely corrected for temperature drift in the loop by using two reference measurements at the beginning and end of a section run and assuming constant change during the time a core section is measured. The data were stored in the ODP Janus database as raw instrument units and were not corrected for changes in sediment volume. To obtain SI units, these instrument units need to be multiplied by ~0.68 x 10–5, although exact conversions are best done using control measurements on discrete samples, correcting for the actual core volume measured (Blum, 1997).
GRA bulk density measurements allow estimation of wet bulk densities by measuring the attenuation (Compton scattering) of gamma radiation passing through the unsplit core sections. GRA bulk density data are most reliable in undisturbed cores and can often be directly correlated with the downhole density logs. In disturbed cores, GRA density is underestimated. Calibration was performed using a series of water/aluminum core segments.
P-wave velocity was estimated using two measurement devices: the PWL on the MST and the PWS3 system (essentially a "Hamilton Frame") on the split core. Both systems send 500-kHz P-wave pulses through the core and the core liner at a frequency of 1 kHz. The transmitting and receiving transducers are aligned perpendicular to the core. Displacement transducers monitor the separation between the P-wave transducers, and the distance is used to convert traveltime into velocity after correcting for the liner. Good coupling between the liner and the core is crucial for obtaining reliable measurements. Calibration of the displacement transducers is performed using a series of acrylic blocks of known thicknesses. The P-wave traveltime and measurement of electronic delay within the PWL circuitry were calibrated using a plastic bag filled with distilled water. The bag was manipulated to sit between the transducers at varying distances. Repeated measurement of P-wave velocity through a core liner filled with distilled water was used to check the calibration validity. Velocity data were not corrected for in situ temperature and pressure. These corrections can be made using the relationships outlined in Wyllie et al. (1956), Wilson (1960), and Mackenzie (1981).
NGR emissions result from the decay of radioactive isotopes and were measured in the laboratory by scintillation detectors. Results were reported in counts per second, which can then be compared qualitatively with the downhole logging data. NGR calibration was performed at the beginning of the leg.
The Non-Contact Resistivity (NCR) system measures the electrical conductivity of sediments and rocks through the core liner. Combination logs of resistivity and density provide pertinent lithologic information (grain size/permeability/tortuosity) that cannot be achieved with other nondestructive measurements. The NCR technique operates by inducing a high-frequency magnetic field in the core, from a transmitter coil, which in turn induces electrical currents in the core that are inversely proportional to the resistivity. Very small magnetic fields regenerated by the electrical current are measured by a receiver coil. To measure these very small magnetic fields accurately, a difference technique has been developed that compares the readings generated from the measuring coils to the readings from an identical set of coils operating in air. This technique provides the requisite accuracy and stability required. Resistivities between 0.1 and 10 
m can be measured at spatial resolutions of 2 cm along the core. Resistivity measurements vary with core temperature and should be obtained in a stable temperature environment for best results. Calibration is achieved by filling the core liner with water of known salinities (and hence known resistivities) and nomalizing the core measurement results with the reference measurements.
Porosity, grain density, and bulk density of 10-cm3 sediment specimens were calculated from measurements of wet and dry sediment mass and dry sediment volume. Wet and dry sample mass was determined with a reproducibility of ±3% standard deviation using a Scientech electronic balance that compensates for the ship's motion. Wet sample mass was measured immediately after collection. Dry sample mass and dry sediment volume were measured after the samples had been dried in a convection oven at 105° ± 5°C for 24 hr and allowed to cool in a desiccator. Dry sample volume was determined using a Quantachrome penta-pycnometer, a helium-displacement pycnometer. Sample volumes were determined at least five times, until readings were consistent (volume error within 1%). The principles and calculations are summarized in Blum (1997).
Thermal conductivity is the measure of a material's ability to transmit heat by molecular conduction. Thermal conductivity and temperature measurements of sediments and rock sections are used to determine heat flow. Heat flow is not only characteristic of the material but is also an indicator of type and age of ocean crust and fluid circulation processes at shallow and great depths. Thermal conductivity was measured in soft sediments using the TK04 measurement system (see Blum, 1997), with the needle-probe method in full-space configuration (Von Herzen and Maxwell, 1959), after the core had equilibrated to ambient temperature. The full-space needle, containing a heater wire and calibrated thermistor, was inserted into the sediment through a small hole drilled into the core liner. Measurement errors are 5%–10%.
