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doi:10.2204/iodp.proc.344.102.2013

Physical properties

Physical properties measurements provide fundamental information required to characterize lithostratigraphic units, basement properties, and hydrogeology and allow for the correlation of cored materials with logging data. A comprehensive discussion of methodologies and calculations used in the JOIDES Resolution Physical Properties Laboratory is presented in Blum (1997). Two additional measurement types and one additional measurement tool not described in Blum (1997) were used during this expedition. These consisted of electrical conductivity, which provides information relevant to chemical diffusion, and anelastic strain recovery, which provides information on stress orientation. A needle penetrometer, which covers a higher range of compressive strength than the standard pocket penetrometer, was used for indurated sediments.

Recovered whole-round cores were first allowed to thermally equilibrate to an ambient room temperature of ~20°C (~3 h). After thermally equilibrating, core sections longer than 30 cm were run through the WRMSL for measurement of gamma ray attenuation (GRA) density, magnetic susceptibility, and compressional wave velocity (P-wave Logger [PWL]). Sections longer than 50 cm were measured with the spectral NGRL.

For cores with soft sediments, thermal conductivity measurements were carried out on whole-round core sections using the needle probe technique. For lithified sediments, thermal conductivity was measured on split cores using the half-space technique.

After the cores were split into archive and working halves, digital image scanning was carried out on the cut surfaces of archive core halves using the SHIL. Following the SHIL, the archive half of the core was passed through the SHMSL for measurement of point magnetic susceptibility and color spectrophotometry. The SHMSL uses a laser to record relief along the core, which yields information about the location of gaps and cracks between core pieces.

Discrete samples for moisture and density (MAD) measurements were taken from the working half at a frequency of approximately one per section. MAD measurements yield wet bulk density, dry bulk density, grain density, water content, void ratio, and porosity.

P-wave velocity was measured on the working half of cores. Electrical conductivity was measured at a frequency of approximately one per section and was used to estimate formation factor. Shear strength was measured using the automated vane shear (AVS) apparatus, and compressive strength was measured using pocket and needle penetrometers.

Whole-Round Multisensor Logger measurements

GRA bulk density, P-wave velocity, and magnetic susceptibility were measured nondestructively with the WRMSL. To optimize WRMSL performance, sampling intervals and measurement integration times were the same for all sensors. The sampling interval was set at either 1 or 2.5 cm (depending on available time) with an integration time of 5 s for each measurement. GRA performance was monitored by passing a single core liner filled with deionized water through the WRMSL after every core.

In general, measurements are most effective with a completely filled core liner with minimal drilling disturbance. For APC sediment cores, the 66 mm core liner width is generally filled. Cores recovered using the XCB and RCB have a diameter smaller than the core liner. Because the reported bulk density values assume a 66 mm diameter, GRA bulk density measurements from XCB and RCB cores tend to underestimate true values. Sections consisting of discontinuous fragments were not measured with the WRMSL sensors.

Gamma ray attenuation bulk density

The GRA densiometer on the WRMSL operates by passing gamma rays from a ¹³⁷Cs source through a whole-round core into a 75 mm × 75 mm sodium iodide detector situated directly above the core. The gamma ray peak has a principal energy of 0.662 MeV and is attenuated as it passes through the core (Evans, 1965; Harms and Choquette, 1965). The attenuation of gamma rays, mainly by Compton scattering, is related to the material bulk density and thickness of the sample. The gamma ray count is proportional to density. Bulk density, ρ, determined with this method can be expressed as

where

• µ = Compton attenuation coefficient,
• d = sample diameter,
• I₀ = gamma ray source intensity, and
• I = measured intensity of gamma rays passing through the sample.

The attenuation coefficient and gamma ray source intensity are treated as constants, such that ρ can be calculated from I. The gamma ray detector is calibrated with a set of aligned aluminum cylinders of various diameters surrounded by distilled water in a sealed core liner that is the same as that used during coring operations. The relationship between I and the product of µ and d can be expressed as

where A, B, and C are coefficients determined during calibration. Gamma ray counts through each cylinder were determined for a period of 60 s, and the natural log of resulting intensities was plotted as a function of µd. Here density of each aluminum cylinder was 2.7 g/cm³ and d was 1, 2, 3, 4, 5, or 6 cm. The WRMSL provided the values of I and µ, and ρ was calculated with the above equation. Recalibration was performed as needed if the deionized water standard after every core deviated significantly (more than a few percent) from 1 g/cm³. The spatial resolution of the GRA densiometer is <1 cm.

Magnetic susceptibility

Magnetic susceptibility, k, is a dimensionless measure of the degree to which a material can be magnetized by an external magnetic field:

where M is the magnetization induced in the material by an external field strength H. Magnetic susceptibility responds to variations in the magnetic composition of the sediment that commonly can be related to mineralogical composition (e.g., terrigenous versus biogenic materials) and diagenetic overprinting. Materials such as clay generally have a magnetic susceptibility several orders of magnitude lower than magnetite and some other iron oxides that are common constituents of igneous material. Water and plastics (core liner) have a slightly negative magnetic susceptibility.

The WRMSL incorporates a Bartington Instruments MS2 meter coupled to a MS2C sensor coil with an 88 mm diameter and operates at a frequency of 565 Hz. The sensor output was set to record in instrument units. Data shown here and within the database are not corrected for volume effects due to differing APC, XCB, and RCB core diameters or varying sample bulk densities. The instrument is calibrated with a homogeneous mixture of magnetite and epoxy in a 40 cm long piece of core liner to an accuracy of ±5%. The spatial resolution of the method is ±4 cm; therefore, core material that is not continuous over an 8 cm interval will underestimate the magnetic susceptibility.

Compressional wave velocity

The compressional wave velocity sensor measures the ultrasonic P-wave velocity of the whole-round sample residing in the core liner. The PWL transmits a 500 kHz P-wave pulse across the core section at a specified repetition rate. This signal is coupled to the sample by the plastic pole contacts of the transducers clamped to the sides of the core by the linear actuator. Frequently, water is used to improve coupling between the transducers and the liner. The plastic pole contacts and the pressure applied by the actuator are generally sufficient for reliable P-wave velocity measurement. The transmitting and receiving ultrasonic transducers are aligned so that wave propagation is perpendicular to the long axis of the core section. Torque applied by the actuator can be set by the user to ensure good acoustic contact between the liner and the core material. Because of poor contact between the core liner and XCB and RCB cores, WRMSL P-wave velocity was generally not measured on those cores.

The basic relationship for sonic velocity, V, is

where d is the path length of the wave through the core and t is the traveltime. Besides the traveltime through the sample, the total traveltime between the transducers includes three additional components:

• t_delay = time delay related to transducer faces and electronic circuitry),
• t_pulse = delay related to the peak detection procedure), and
• t_liner = transit time through the core liner).

The system is calibrated using a core liner filled with deionized water. For routine measurement on whole-round cores inside core liners, the corrected core velocity, V_core, can be expressed by

where

• d′_core = measured diameter of core and liner,
• d_liner = liner wall thickness, and
• t₀ = measured total traveltime.

Traveltime is determined by signal processing software that automatically detects the first arrival of the P-wave signal to a precision of 50 ms. It is a challenge for an automated routine to pick the first arrival of a potentially weak signal if background noise is high. The search method skips the first positive amplitude and finds the second positive amplitude using a detection threshold limit, typically set to 30% of the maximum amplitude of the signal. The program then finds the preceding zero crossing and subtracts one wave period to determine the first arrival. To avoid extremely weak signals, a minimum signal strength can be set (typically 0.02 V) and weaker signals are ignored. To avoid signal interference at the beginning of the record from the receiver, a delay (typically 0.01 ms) can be set to force the amplitude search to begin in the quiet interval preceding the first arrival. In addition, a trigger (typically 4 V) is selected to initiate the arrival search process, and the number of waveforms to be stacked (typically five) can also be set. A linear voltage differential transformer measures the separation of the transducer to derive a signal path length (i.e., the core diameter). After corrections for system propagation delay, liner thickness, and liner material velocity, the ultrasonic P-wave velocity is calculated.

Natural Gamma Radiation Logger measurements

The NGRL measures gamma radiation emitted from whole-round core sections arising primarily from the decay of ²³⁸U, ²³²Th, and ⁴⁰K isotopes. The main NGR detector unit consists of 8 sodium iodide (NaI) scintillator detectors, 7 plastic scintillator detectors, 22 photomultipliers, and passive lead shielding. The NaI detectors are covered by 8 cm of lead shielding. In addition, lead separators (~7 cm of low-background lead) are positioned between the NaI detectors. Half of the lead shielding closest to the NaI detectors is composed of low-background lead, whereas the outer half is composed of regular (virgin) lead. In addition to passive lead shielding, the NGRL employs a plastic scintillator to suppress the high-energy gamma and muon components of cosmic radiation by producing a canceling signal when these charged particles pass through the plastic scintillators. The NGRL was calibrated using a source consisting of ¹³⁷Cs and ⁶⁰Co and identifying the peaks at 662 keV (¹³⁷Cs) and 1330 keV (⁶⁰Co). Calibration materials are provided by Eckert & Ziegler Isotope Products, Valencia, California (USA).

For presentation purposes, the counts were summed over the range of 100–3000 keV. Background measurements of an empty core liner counted for 20,000 s (5 h) were made upon arrival at each site. Over the 100–3000 keV integration range, background counts averaged 4–5 cps.

A measurement run consisted of eight simultaneous measurements offset by 20 cm each. The quality of the energy spectrum measured in a core depends on the concentration of radionuclides in the sample but also on the counting time, with higher times yielding better spectra. The available count time in each position depended on core flow. For sediment cores, counting times were generally 10 min. For basement cores, counting times were extended as allowed by available time.

Section Half Multisensor Logger measurements

The SHMSL measures magnetic susceptibility and spectral reflectance on core section halves. The archive half of the split core is placed on the system’s core track. An electronic platform moves along a track above the core section, recording the sample height with a laser sensor. The laser establishes the location of the bottom of the section, and the platform reverses the direction of movement, moving from bottom to top making measurements of point magnetic susceptibility and spectral reflectance data at 2.5 cm intervals.

Color reflectance spectrometry

Reflectance is measured from 171 to 1100 nm wavelength at 2 nm intervals using a halogen light source, covering a wavelength from ultraviolet through visible to near-infrared. The scan of the entire wavelength range takes ~5 s per data acquisition offset. The data are generated using the L*a*b* color system, in which L* is luminescence, a* is the blue + green value, and b* is the red + green value. The color reflectance spectrometer calibrates on two spectra, pure white (reference) and pure black (dark). Color calibration was conducted approximately every 12 h.

Point magnetic susceptibility

Point magnetic susceptibility is measured using a contact probe with a flat, 15 mm diameter sensor operating at a frequency of 0.580 kHz. The sensor takes and averages three measurements at 0.1 attenuation for each offset to an accuracy of 5%. The spatial resolution of the magnetic susceptibility point instrument is 2 cm, making it advantageous over whole-round magnetic susceptibility measurements for basement cores consisting of broken pieces <8 cm long (the spatial resolution of whole-round magnetic susceptibility). Results are reported in dimensionless instrument units. The point magnetic susceptibility meter was calibrated by the manufacturer before installation on the ship. The probe is zeroed in air before each measurement point, and a background magnetic field is measured (influence from metal track, etc.) and removed from the measured value before data are recorded.

Thermal conductivity

Thermal conductivity is a measure of the ease at which heat flows through a material and is dependent on composition, porosity, and structure. Thermal conductivity was measured on unconsolidated sediment and rock samples using the full-space needle probe (Von Herzen and Maxwell, 1959) and the half-space line source (Vacquier, 1985), respectively. Both the full- and half-space methods approximate the heating element of an infinite line source (Blum, 1997). These measurements produce a scalar value in a plane perpendicular to the orientation of the probe. All measurements were made after the cores had equilibrated to ambient laboratory temperature. After the background thermal drift was determined to be stable, the heater circuit was closed and the increase in the probe temperature was recorded.

In porous rocks, temperature influences thermal conductivity in two competing ways. The thermal conductivity of rock matrix is inversely related to temperature (Zoth and Haenel, 1988), whereas the thermal conductivity of water increases with temperature (Keenan et al., 1978). Reported thermal conductivity values are at laboratory temperatures and have not been corrected to in situ temperature. Previous studies suggest a correction of +5% for each +20°C change in temperature between the laboratory and in situ conditions for a high-porosity, water-saturated sediment (Ratcliffe, 1960) and –3% for several hard rocks (Clark, 1966).

For soft sediment, a full-space single-needle probe TeKa TK04 unit (Blum, 1997) was utilized to measure thermal conductivity of whole cores. To insert this probe, a hole was made in the core liner at a position based on visual inspection of the core to avoid disturbed regions. A rubber insulator was sometimes wrapped around the core and the lower portion of the probe before placing the section in a box to reduce ambient temperature variations and speed up temperature drift calibration times. Temperature-time series were acquired over ~80 s. Values of thermal conductivity are based on the observed rise in temperature for a given quantity of heat. In most cases, repeated measurements were made at the same location, and in these cases the probe was left in place and the sample was left to re-equilibrate for 5 to 10 min prior to the next measurement.

Thermal conductivity on lithified samples was measured on the working half of the split core with the thermal conductivity meter in half-space mode (Vacquier, 1985). Samples must be smooth and flat to ensure adequate contact with the heating needle. Visible saw marks were removed when necessary by grinding the split surface with 120–320 gauge silicon carbide powder.

Moisture and density

Several basic quantities of interest (water content, bulk density, dry density, porosity, and void ratio) are found most accurately through mass and volume determinations on discrete samples. The shipboard MAD facility on the JOIDES Resolution includes a dual-balance system and a pycnometer with six cells. Sediment samples were measured in vials, and the mass and volume of the vials were subtracted to determine sediment mass and dry volume.

Immediately after sediment samples were collected, the vials were capped until weighing to prevent moisture loss. As soon as possible after collection, the wet sediment mass (M_wet) was measured. Dry sediment mass (M_dry) and volume (V_dry) were measured after drying the samples in a convection oven for >24 h at a temperature of 105° ± 5°C and then cooling in a desiccator for >1 h. The dual-balance system was used to measure both wet and dry masses. Two Mettler-Toledo XS204 balances were used to compensate for ship motion, one acting as a reference and the other for measurement of the unknown. A standard weight of similar value to the sample was placed upon the reference balance to increase accuracy. The default setting of the balances is 300 measurements (taking ~1.5 min).

Dry volume was measured using a helium-displacement pycnometer with a nominal precision of ±0.04 cm³. The pycnometer system measures dry sample volume using six pressurized, helium-filled chambers. At the start of the expedition, and whenever the helium gas tank was changed, shipboard technicians performed a calibration using stainless steel spheres of known volume. Each pycnometer chamber was tested at least once a day by running spheres of known volume. Spheres are assumed to be known to be within 1% of their total volume. Individual volume measurements were preceded by three purges of the sample chambers with research grade (99.995% or better) helium heated to 28°C followed by three data acquisition cycles. Each reported value consists of an average of the three measurements.

For calculation of sediment bulk density, dry density, grain density, porosity, and void ratio, the traditional ODP method was used (Method C; Blum, 1997). Water content, porosity, and void ratio are defined by the mass or volume of extracted water before and after removal of interstitial pore water through the drying process. Standard seawater density (1.024 g/cm³) is used for the density of pore water.

Water content (W_c) was determined following the methods of the American Society for Testing and Materials (ASTM) designation D2216 (ASTM International, 1990). Corrections are required for salt when measuring the water content of marine samples. In addition to the recommended water content calculation in ASTM D2216 (i.e., the ratio of pore-fluid mass to dry sediment mass [% dry wt]), we also calculated the ratio of pore-fluid mass to total sample mass (% wet wt). The equations for water content are

and

where

• M_t = total mass of the saturated sample,
• M_d = mass of the dried sample, and
• r = salinity.

Bulk density, ρ, is the density of the saturated samples, with ρ = M_t/V_t. The mass, M_t, was measured using the balance, and V_t was determined from the pycnometer measurements of grain volume and the calculated volume of the pore fluid (V_t = V_pore + V_d).

Porosity, ϕ, was calculated using

where

• ρ = calculated bulk density,
• ρ_w = density of the pore fluid, and
• W_c = water content expressed as a decimal ratio of percent dry weight.

Grain density, ρ_grain, was determined from measurements of dry mass and dry volume made in the balance and in the pycnometer, respectively. Mass and volume were corrected for salt using

where s is the salt content (in grams) and ρ_salt is the density of salt (2.257 g/cm³).

Compressional wave velocity

Discrete compressional wave velocity measurements were obtained on sediment cores at a frequency of 1 per section where conditions allowed. X-axis measurements were acquired with a caliper-type contact probe with one plastic transducer contact on the face of the working half of the core and the other contact against the core liner. Y- and z-axis measurements were acquired using two pairs of bayonet probes inserted perpendicular and parallel to the face of the working half, respectively.

For indurated sediments, P-wave velocities were measured on the split core using the x-axis caliper-type contact probe transducers on the P-wave velocity gantry. The system uses Panametrics-NDT Microscan delay line transducers, which transmit at 500k Hz. To maximize contact with the transducers, deionized water was applied to sample surfaces.

The signal received through the sample was recorded by the computer attached to the system, and the peak of the initial arrival was chosen either with autopicking software or by manual picking based on operator evaluation. The complete waveform is stored with the data in case reanalysis is deemed necessary. The distance between transducers was measured with a built-in linear voltage displacement transformer (LDVT).

Calibration was performed each day before measurements were made with a series of acrylic cylinders of differing thicknesses and known P-wave velocity of 2750 ± 20 m/s for the caliper-type contact probe and water for the bayonet probes. The determined system time delay from calibration was subtracted from the picked arrival time to yield a traveltime of the P-wave through the sample. The thickness of the sample (calculated by LDVT in meters) was divided by the traveltime (in seconds) to calculate a P-wave velocity in meters per second.

Downhole temperature measurements

Downhole temperature measurements were made using the advanced piston coring temperature tool (APCT-3). The APCT-3 consists of three components: electronics, coring hardware, and computer software. The temperature sensors were calibrated for a working range of 0° to 45°C. Prior to entering a hole, each instrument is held at the mudline for ~10 min to equilibrate with bottom water temperature. After bottom water temperature equilibration, the tools are lowered in the hole to penetrate the formation. The penetration of each tool into the formation generates a rise in temperature caused by frictional heating. Following the initial temperature rise, temperatures decrease along a decay curve to near equilibrium. During this decay phase, it is important that the temperature tool is not disturbed. A second rise in temperature occurs because of frictional heating as the tool is pulled out of the formation. Temperatures were measured as a time series with a sampling rate of 1 s and logged onto a microprocessor within the downhole tool. The data were retrieved when the tool was recovered. The formation equilibrium temperature was determined based on fitting the temperature decay curve using the MATLAB TP-Fit program (M. Heeseman et al., pers. comm., 2008).

If heat transfer is conductive and constant with depth through the sediment, the thermal gradient will be inversely proportional to thermal conductivity according to Fourier’s law. This relationship can be linearized by plotting temperature as a function of summed thermal resistance (Bullard, 1939):

, i = 1;n

where

• T = temperature,
• z = depth,
• T₀ = bottom water temperature,
• Q = heat flow, and
• = thermal resistance.

Where thermal conductivity data were available throughout the borehole, the above equation was used to estimate the borehole temperature profile.

Shear and compressive strength

Undrained sediment strength was measured using the AVS, a pocket penetrometer, and a needle penetrometer. Measurements were not performed at in situ stress conditions and thereby underestimate the true undrained peak shear strength in situ. Measurements were made with the vane rotation axis and penetrometer penetration direction perpendicular to the split surface.

Undrained shear strength (τ_fu) was measured in fine-grained plastic sediment using the AVS system following the procedures of Boyce (1977). The vane rotation rate was set to 90°/min. Peak undrained shear strength was measured typically once per >100 cm section. The instrument measures the torque and strain at the vane shaft using a torque transducer and potentiometer. To minimize disturbance effects resulting from the measurement itself, vane shear tests were generally conducted first, followed by penetrometer tests. Vane shear strength, S_u(v) (kPa), is calculated as

where T is the torque required to cause the material to fail (N·m) and K_v is the constant depending on vane dimensions (cubic meters) (Blum, 1997).

All AVS measurements reported were obtained using a vane with a height and diameter of 12.7 mm. Failure torque was determined by measuring the degrees of rotation of one of four torsional springs and a manufacturer-specified linear calibration equation relating the rotation angle to torque for the particular spring being used. Selection of the appropriate spring was based on the anticipated shear strength of the material. Vane shear results were generally considered reliable for shear strength values less than ~150–200 kPa, above which excessive cracking and separation of the core material occurred.

Two penetrometers were used to measure compressive strength. A pocket penetrometer was used for soft sediment, and a needle penetrometer was used for lithified sediment. Penetration measurements were all conducted on the split core face. The Geotester STCL-5 pocket penetrometer is a spring-operated device used to measure compressive strength by pushing a 0.25 inch (6.4 mm) diameter probe 0.25 inches (6.4 mm) deep (to the red marker) below the split-core surface. The mechanical scale of compressive strength is in units of kilograms per square centimeter, which are converted into units of kilopascals for reporting as follows:

A 1 inch diameter adaptor foot is available for measuring in very soft sediment. This provides a 16 times increase in area. In addition, for sediment strength in the middle range between the two adaptors, another adaptor foot 0.478 inches (12.14 mm) in diameter was made during the expedition. When the 1 inch diameter foot is used, the scale readings are multiplied by 0.0625, and when the 0.478 inch diameter foot is used, they are multiplied by 0.228484. In the database, the adaptor feet are designated “A” (1 inch diameter adaptor foot), “M” (0.478 inch diameter medium adaptor foot), or “Non” (no adaptor foot). The maximum compressive strength that can be measured with the pocket penetrometer is 220 kPa.

In the case of indurated sediment, a third-party needle penetrometer (SH-70, MARUTO Testing Machine Company, Japan) that covers a much higher range than the pocket penetrometer (>220 kPa) was used. For the needle penetrometer, the equation to estimate a uniaxial compressive strength, Δσ_f, is

or

where NP is the penetration force (N) divided by penetration depth into sediment (mm). The minimum and maximum NP that can be measured are 1 and 100 N/mm, respectively, which is equivalent to 410 and 37,000 kPa of compressive strength, respectively. Measurements using one of the two penetrometers were typically performed once per section, with a higher frequency from 0 to 3 mbsf.

Electrical conductivity and formation factor

Formation factor was determined from electrical conductivity measurements taken adjacent to every MAD measurement on split sediment cores using a third-party tool (University of Rhode Island, USA). Formation factor is used to estimate pore space tortuosity and may be used to quantify chemical diffusivities. For these measurements, two in-line electrodes, 1.5 cm long, spaced 1 cm apart in a block of nonconducting flouoropolymer and attached to a Metrohm 712 conductometer, were inserted into the split-core sediment in the direction of y and z.

At each sampling location, measurements of sediment conductivity, χ_sed (the inverse of resistivity, R_core), and sediment temperature were made. Measurements of IAPSO seawater conductivity, χ_IAPSO, and temperature were made at the beginning and end of each site. Measurement of a seawater standard conductivity, χ_sw, and its temperature were made before and after each core for use in tracking instrument drift. The seawater standard was obtained by pumping seawater from ~4 m below the sea surface at Site U1381 for measurements at Sites U1381 and U1380 and from Site U1412 for Sites U1412–U1414.

Both seawater and sediment measurements of electrical conductivity were adjusted to a standard temperature of 20°C, where the correction factor is given by a fifth-order polynomial (Janz and Singer, 1975):

where

• a = 29.05128,
• b = 0.88082,
• c = –1.98312 × 10^–4,
• d = 3.3363 × 10^–4,
• e = –1.0776 × 10^–5, and
• f = 1.12518 × 10^–7.

The temperature corrected measurement, σ_T, is given by

where σ is the measurement and χ₂₀ and χ_obs are the correction factors using 20°C and the observed temperature, respectively. Both seawater and sediment measurements of electrical conductivity are adjusted for the effects of temperature. A linear drift correction based on the seawater standard measurements is computed and applied to the sediment temperature-adjusted measurements. The formation factor, F, is computed as

where

• S_pw = measured salinity of the pore water,
• S_IAPSO = salinity of the IAPSO standard (34.995),
• α = 1.169, and
• β = 5.196.

The values of α and β were determined by a least-squares fit to measured values of salinity and conductivity of 100%, 80%, 66.7%, and 50% seawater, which spans the range of salinities that were expected at the sites being cored as part of Expedition 344. This simple method for determining formation factor does not account for surface conductivity effects of the sediment matrix.

Anelastic strain recovery analysis

The anelastic strain recovery (ASR) technique is a core-based stress measurement that can evaluate both the orientation and magnitude of the 3-D principal stress tensor. The ASR technique is principally used to measure the anelastic strain change due to releasing the stress soon after core recovery. ASR measurements during Expedition 344 followed the methodology of Matsuki (1991), with guidelines described in Lin et al. (2007), and were made using a third-party instrument (JAMSTEC, Japan).

Soon after a 15 cm long fresh whole-round core was taken on the catwalk, WRMSL measurements were carried out. Because ASR measurements are very time sensitive, WRMSL measurements were conducted prior to thermal equilibration. The core samples were extruded from core liners, the outer surface was washed in seawater to remove drilling mud, and the surfaces were air-dried at room temperature and marked with reference lines at 45° intervals to ensure that strains were measured in at least nine directions, six of which were independent (18 wire strain gauges: 6 cross gauges and 6 single gages). It took 1–2 h to insert all strain gauges, and the total elapsed time after core on deck was 1–2 h before we started recording the strain (core diameter) changes.

To prevent volumetric changes associated with pore fluid evaporation and temperature change, the core samples were triple bagged (i.e., with two plastic bags and an aluminum bag) and submerged in a thermostatic chamber where temperature changes were kept controlled within less than ±0.1°C from the room temperature (23°C) during measurement. All strain data were collected every 10 min for a maximum of 14 days. ASR results were not available shipboard during Expedition 344, so are not included in the site reports. Data are available from IODP by request.

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