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doi:10.2204/iodp.proc.348.102.2015

Physical properties

Physical property measurements provide valuable constraints on bulk physical character to augment lithologic unit characterization and to facilitate correlation of seismic reflection data with discrete core and cuttings measurements and descriptions. Thus, these data provide information necessary for reliable cuttings-core-log-seismic integration. Expedition 348 employed multiple approaches and methods to characterize the physical properties of cuttings and cores.

Prior to core physical property measurements, XRCT images were collected for all cores, and cores were equilibrated to room temperature (~20°C). After temperature equilibration, whole-round core sections were processed in the MSCL-W to measure gamma ray attenuation (GRA) density, magnetic susceptibility, natural gamma radiation (NGR), P-wave (compressional) velocity, and electrical resistivity. After cores were split into archive and working halves, MAD, electrical resistivity, and P-wave velocity measurements were performed on discrete samples of cores from the working halves. Thermal conductivity measurements were made on working halves using the TeKa thermal conductivity meter in the half-space mode (HLQ). High-resolution digital image photography and color reflectance measurements were performed on archive halves using the MSCL-I and MSCL-C.

For cuttings recovered in Holes C0002N and C0002P (870.5–2330.5 and 1955.5–3058.5 mbsf), limited measurements were conducted due to the low amount of the available material. Unwashed cuttings were analyzed for NGR employing the MSCL-W to determine variations in the radioactive counts of the samples and for correlation with LWD gamma ray measurements. Cuttings were rinsed with seawater to remove contamination from drilling mud and then sieved into 0.25–1, 1–4, and >4 mm size fractions. Washed cuttings samples (~40 cm³ each) were taken from the 1–4 and >4 mm fractions for physical property measurements, including MAD, magnetic susceptibility, dielectric permittivity, and electrical conductivity. Handpicked cuttings were also used for MAD measurements to avoid sampling the DICAs and pillow cuttings (see “Introduction and operations”). In addition, electrical resistivity and P-wave velocity measurements were performed on large handpicked cuttings.

MSCL-W

Whole-round cores were scanned as the core section passed through the MSCL-W. Unwashed bulk cuttings for NGR analysis were packed into a 12 cm long core liner, producing a volume of 400 cm³, and measured with the MSCL-W NGR unit.

Gamma ray attenuation density

Bulk density can be used to evaluate pore volume in sediment, which provides information on the consolidation state of the sediment. GRA density is based on the detection of a gamma ray beam produced by a cesium source. The beam, produced by a ¹³⁷Cs gamma ray source at a radiation level of 370 MBq within a lead shield with a 5 mm collimator, is directed through the whole-round cores. The gamma ray detector includes a scintillator and an integral photomultiplier tube to record the gamma rays that pass through the whole-round core. GRA bulk density (ρ_b) is calculated as

where

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

The Compton attenuation coefficient (µ) and source intensity (I₀) are treated as constants, so ρ_b can be calculated from I. The system is calibrated with a special sealed calibration “core section” composed of a set of aligned aluminum cylinders of various diameters (e.g., 1–6 cm) surrounded by distilled water in a sealed core liner. Density depends on the diameter of the aluminum cylinder and ranges from ρ = 1 g/cm³ (water only) to 2.71 g/cm³ (aluminum only). To calibrate the instrument, gamma ray counts were taken for each aluminum cylinder for a count time of 60 s. The resulting ln(I) was plotted against the product of the known parameters ρ and d of the calibration core section and fitted with a regression line of the following type:

where d is the internal diameter of the core liner (e.g., 7.3 cm for SD-RCB and 6.6 cm for standard RCB) and A, B, and C are coefficients determined from the polynomial equation fit. Density measurements on core samples were conducted perpendicular to the core axis every 4 cm along the core.

Magnetic susceptibility

Magnetic susceptibility is the degree to which a material can be magnetized by an external magnetic field. Therefore, magnetic susceptibility provides information on sediment mineral composition, but is more generally used to help correlation between boreholes drilled in the same formation. A Bartington loop sensor with an 8 cm diameter was used to measure magnetic susceptibility. An oscillator circuit in the sensor produces a low-intensity (~80 A/m root-mean-square) nonsaturating alternating magnetic field (0.565 kHz). This pulse frequency is converted into magnetic susceptibility. The spatial resolution of the loop sensor is 23–27 mm, and it is accurate to within 5%. Magnetic susceptibility data were collected every 4 cm along the core.

Natural gamma radiation

NGR measurements provide insights into sediment composition, which can be used to identify lithology. Whole-round cores and unwashed cuttings packed in a 12 cm long core liner were monitored for NGR emissions to obtain spatial variability in radioactivity and to establish gamma ray logs of cores for correlation to downhole gamma ray logs. A lead-shielded counter, optically coupled to a photomultiplier tube and connected to a bias base that supplies high-voltage power and a signal preamplifier, is used. Two horizontal and two vertical sensors are mounted in a lead, cube-shaped housing. The NGR system records radioactive decay of long-period isotopes ⁴⁰K, ²³²Th, and ²³⁸U. NGR has a resolution of 120–170 mm and was measured every 16 cm with a count time of 30 s. Background radiation noise was determined by taking measurements on a water-filled calibration core.

P-wave velocity

P-wave velocity data can be used to evaluate small-strain moduli; to correlate among log, core, and seismic data; and to evaluate pore structure and cementation. P-wave (compressional) velocity (V_P) is defined by the time required for a compressional wave to travel a set distance:

where d is the path length of the wave across the core and t_core is traveltime through the core.

P-wave velocity transducers on the MSCL-W system measure total traveltime of the compressional wave between transducers. The wave travels horizontally across the whole core and core liner. The total traveltime observed is composed of

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

The system is calibrated using a core liner filled with distilled water, which provides control for t_delay, t_pulse, and t_liner. With these calibrations and assuming that the core completely fills the core liner, core velocity (V_P) can be calculated on whole-round specimens in core liners as follows:

where

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

Electrical resistivity

Electrical resistivity may be useful for estimating other sediment physical properties, including porosity, tortuosity, permeability, and thermal conductivity, although resistivity data must be used with caution because the value is sensitive to all of these parameters, as well as to salinity of pore fluid and mineralogy. Bulk electrical resistivity is controlled by solid grain resistivity, interstitial water resistivity, pore space distribution, and pore connectivity. The noncontact resistivity sensor on the MSCL-W system induces a high-frequency magnetic field in the core with a transmitter coil. This generates an electrical current in the bulk sediment that is inversely proportional to its resistivity. A receiver coil measures the secondary magnetic field generated by this induced electrical current. To measure this smaller magnetic field accurately, a differencing technique has been developed that compares readings from the sample core to readings from an identical set of coils operating in air. Electrical resistivity is estimated from an empirical equation,

where ρ is the electrical resistivity (Ωm) and E is the sensor response (mV).

The coefficients a and b are obtained by the calibration measurements on five reference core liners filled with different concentrations of NaCl solution (0.35, 1.75, 3.5, 17.5, and 35 g/L). Electrical resistivity data were obtained at 4 cm intervals on the MSCL-W.

Magnetic susceptibility (washed cuttings)

For magnetic susceptibility analysis, ~10 cm³ of vacuum-dried cuttings from the 1–4 and >4 mm size fractions were placed into a paleomagnetic (pmag) cube. Cubes were weighed empty and then filled with the vacuum-dried cuttings material. The prepared cube, with a volume of 7 cm³, was then analyzed with the Kappabridge KLY 3S system (AGICO, Inc.). Sensitivity for the measurement is 3 × 10^–8 SI, and intensity and frequency of the field applied are 300 mA/m and 875 Hz, respectively. A standard was measured once a day to ensure long-term quality of the system calibration. A blank empty cube was measured to determine background impact before each sample measurement.

Moisture and density measurements

The purpose of MAD measurements is to obtain general physical properties of sediment or rock specimens such as bulk wet density, bulk dry density, grain density, water content, porosity, and void ratio. All these properties can be calculated using phase relations in marine sediment from the direct measurements of the wet sample mass (M_wet), the dry sample mass (M_dry), and the dry sample volume (V_dry) (Noorany, 1984). Standard ODP/IODP practices, which include a salt correction, were used to determine interstitial water mass and volume, salt mass and volume, and solid grain mass and volume (Blum, 1997). Standard seawater density (1.024 g/cm³) and salinity (35‰) and a constant salt density (2.22 g/cm³) were assumed for all calculations. MAD measurements were conducted on both cuttings and cores; there is no difference in measurements and calculations between the two sample types, only in sample preparation.

Sample preparation

For core samples, two discrete samples were collected per section for determination of physical properties. MAD samples were taken as a part of cluster samples adjacent to any whole-round core samples including interstitial water, community whole round, and individual requested samples. Sample intervals were chosen at minimally disturbed, homogeneous locations. Special care was taken to avoid drilling mud in MAD samples.

Cuttings samples were taken at 10 m depth intervals of drilling progress for MAD measurement. After being rinsed with seawater, the cuttings of the working portion were separated into different size fractions (0.25–1, 1–4, and >4 mm) by sieving. A volume of ~20 cm³ taken from the 1–4 mm size fraction was used for MAD measurements. Handpicked pieces from the >4 mm size fraction were also used to investigate the difference between DICAs/pillow cuttings and stiffer formation cuttings. Wet cuttings were prepared after sieving to remove excess water by gently wiping cuttings with absorbent paper until no visible water films were observed on the cuttings surfaces. The samples were then placed into a weighed glass jar.

Measurements

The wet sample mass (M_wet) was measured using a paired electronic balance system designed to compensate for the ship’s heave. The sample mass was counterbalanced with a precisely known mass (40 g for sediment). The sample mass was determined to a precision of ±0.01 g. The balance system was calibrated twice a day or more frequently during poor weather conditions. After measurement, the wet samples were placed in a convection oven for >24 h at 105° ± 5°C to dry. The dry samples were then cooled in a desiccator for at least 1 h to equilibrate to room temperature (~20°C), and then the dry mass and volume was measured. The dry mass (M_dry) was determined using the same measuring system. Dry volume (V_dry) was measured using a helium-displacement Quantachrome pentapycnometer with a nominal precision of ±0.04 cm³. The five-chamber system allows the measurement of four sample volumes and one calibration sphere, which was rotated between all measurement chambers to monitor for errors in each chamber. The pycnometer was calibrated at least once per 24 h. An average of four measurements was reported for each sample.

Phase relations in marine sediment

From the direct measurements of M_wet, M_dry, and V_dry, pore fluid mass (M_f), salt mass (M_salt), mass of solids excluding salt (M_s), pore fluid volume (V_f), salt volume (V_salt), and volume of solids excluding salt (V_s) can be obtained by

where

• M_wet = total mass of the wet sample,
• M_dry = mass of the dried sample,
• s = salinity (3.5%),
• ρ_f = density of pore fluid (1.024 g/cm³), and
• ρ_salt = density of salt (2.220 g/cm³).

Calculations of physical properties

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 water content calculation in ASTM D2216 (i.e., the ratio of pore fluid mass to dry sediment mass as percent dry weight), we also calculated the ratio of pore fluid mass to total sample mass (percent wet weight). The equations for water content are

Bulk density (ρ_b), dry density (ρ_d), and grain density (ρ_g) are defined as

where V_wet is the bulk volume of wet sample determined from the dry volume (V_dry), pore fluid volume (V_f), and salt volume (V_salt).

Porosity (ϕ) is the volume of the pores to the total sample volume; void ratio (e) is the pore volume to the volume of the solid grains. They are calculated as

P-wave velocity, electrical conductivity, and dielectric permittivity (cores and cuttings)

P-wave velocity and electrical resistivity measurements were performed on cuttings and cubic samples cut from rock cores with a diamond blade saw. Cubic samples for P-wave velocity and electrical resistivity measurements were ~20 mm × 20 mm × 20 mm. Cubes were cut with faces orthogonal to the x-, y-, and z-axes of the core reference. This three-component measurement plan enables first-order estimation of both P-wave velocity and electrical resistivity anisotropies. P-wave measurements on cuttings were generally made in only one direction. The cuttings were sanded with medium grain abrasive paper in order to form two parallel facets at least 0.5 cm apart. For impedance measurements, handpicked cuttings were reshaped into a flat right prism with abrasive paper. This resulted in the thickness of the platelet ranging from 2.5 to 5–6 mm.

A P-wave logger for discrete samples (PWL-D) was used to measure P-wave velocity. The sample is held between two transducers acting as transmitter and receiver. The PWL-D stand has a laser distance sensor and two interchangeable sets of transducers with resonant frequencies at 230 and 500 kHz, respectively. The transmitting transducer was connected to a pulse generator, and the receiving transducer was connected to an oscilloscope synchronized with the pulse generator. The oscilloscope signal was displayed digitally, and the P-wave total traveltime (t) for the first arrival was picked and recorded. The laser distance sensor provided the sample length (L). The velocity in any direction (i.e., V_Px) was defined by the sample length (i.e., L_x), total traveltime (t_x), and system-calibrated delay time (t_delay):

Traveltime delay was determined by placing the transmitter and receiver in direct contact and measuring traveltime. The laser distance sensor was calibrated by placing the transmitter and receiver into direct contact with each other and then by measuring a 2.5 cm long reference specimen. Quality control measurements were made daily by measuring velocity on acrylic standards with known lengths and acoustic velocities.

Measurements on cores from Hole C0002M were performed with the 230 kHz transducers to minimize attenuation on the less consolidated samples. Measurements on cuttings were performed with the 500 kHz transducers to minimize wavelength so that the ray path always remains more than half the wavelength. Measurements on deep cores (Holes C0002N and C0002P) were also performed with the 500 kHz transducers, as they provide more precision when picking the arrival times. The true average frequency of the wave train transmitted across the sample was found to be 270 and 400 kHz for the 230 and 500 kHz transducers, respectively. Heterogeneous or attenuating samples, as well as samples with irregular shapes, displayed important distortion of the wave train. As the automated pick was on the second zero crossing (rather than on the first arrival), these measurements were discarded as unreliable.

Because P-wave velocity is measured in the x-, y-, and z-directions, the anisotropy is calculated following the approach of Carlson and Christensen (1977). Some sources of anisotropy include (1) alignment of pores during consolidation, (2) fabric development due to alignment of mineral grains, and (3) microstructures such as microfractures and microcracks. The P-wave velocity horizontal-plane anisotropy (α_VPhor) and vertical-plane anisotropy (α_VPvert) calculation compares the horizontal (x and y) and vertical (z) components of P-wave velocity expressed as a percentage of the mean:

Resistivity was measured on the same discrete cubic samples used for P-wave velocity measurements. A cube of known dimensions is held between two electrodes, and complex impedance is measured with a 40 Hz to 110 MHz frequency sweep with the Agilent 4294A impedance analyzer. Sample dimensions are obtained during P-wave velocity measurement. Coupling between the sample and each stainless steel electrode is obtained through insulating plastic film for the measurements of dielectric properties and through a filter soaked in 35 g/L NaCl solution for the measurement of electrical conductivity. The impedance of the sample for each configuration is obtained by subtracting the impedance of the coupling layers from the measured impedance. The impedance of the coupling layers is evaluated by stacking of the two plastic films or the two filters between the electrodes immediately after measuring the impedance of the sample. Sample conductivity (σ_x) and dielectric permittivity (ε_x) in the x-direction are computed from measured real and complex impedance components R_x and X_x by

where L_x, L_y, and L_z are the length of cubic discrete samples in the x-, y-, and z-direction, respectively; R₀ and X₀ refer to the measured impedance of the filter; and f is the frequency. Conductivities in the y- and z-directions are obtained by substitution.

In the case of cuttings, L_y and L_z are not known because the shape of the platelet was generally irregular. Instead, its area (equivalent to L_y × L_z) was calculated by dividing the volume by the thickness (L_x). The volume was determined from the wet weight and dry weight of the platelet and by assuming a grain density as determined from MAD measurement on the corresponding bulk sample of cutting.

Resistivity is calculated as the inverse of the real conductivity. To minimize electrode polarization effects on conductance and to remain consistent with Expedition 315 data and reports, the values of conductivity and resistivity at 10 kHz are reported. Raw data from Expedition 338 have been reprocessed to yield conductivity at 10 kHz and are also given in “Physical properties” in the “Site C0002” chapter (Tobin et al., 2015) (resistivity at 2 kHz are given in Strasser et al., 2014b). The laboratory temperature is also reported for each measurement in order to allow correction to in situ temperature and comparison with logging data. The dielectric permittivity obtained in the 40–110 MHz frequency range of the Agilent 4294A impedance analyzer with saltwater-coupled electrodes is affected by electrode polarization effects and is not reported.

Similar to the P-wave velocity anisotropy, the electrical resistivity horizontal-plane anisotropy (α_Rhor) and vertical-plane anisotropy (α_Rvert) calculation compares the horizontal (x and y) and vertical (z) components of resistivity expressed as a percentage of the mean:

Dielectric permittivity and electrical conductivity (washed cuttings)

Dielectric permittivity is a measure of the electrical polarizability of a material (Von Hippel, 1954). The dielectric permittivity of a sample (ε) is often presented as a product of relative permittivity (ε_r) and vacuum permittivity (ε_o):

Typically dielectric processes occurring on a large scale provide a high dielectric permittivity, but because of extra work required to drive these processes, they also have a longer time constant and “turn off” at a lower frequency. Each dielectric process involves both the displacement of charge carriers (energy absorption), denoted by the real component of the dielectric permittivity (ε′), and work required to achieve polarization (energy dissipation), denoted by the imaginary dielectric permittivity (ε”) along with a characteristic frequency or speed at which it occurs governed by the momentum (and kinematics) of the charge carriers (Guéguen and Palciauskas, 1994), where

Note that conduction also gives rise to energy dissipation, and many dielectric analyses combine both loss mechanisms into one loss term, either expressed as an equivalent imaginary dielectric permittivity (ε”_equiv) or an equivalent conductivity (σ_equiv).

The specific challenges and requirements of Expedition 348 included the need for a very portable system that can be deployed on a ship working at sea where rock and sample preparation opportunities are limited. We used a mobile dielectric laboratory based on the end-loaded transmission line method of Burdette et al. (1980) and Stuchly and Stuchly (1980). This particular method was selected because it is fast, requires <25 g of well-chosen sample, and can be applied to powdered sample, making it ideal for drill cuttings.

End-loaded transmission line dielectric probes use a section of transmission line of known characteristic impedance (determined by the geometry of the inner and outer conductor diameters) that is pressed against the sample. A network analyzer (Agilent 8753D) was used to investigate the change in electromagnetic impedance at the interface between the transmission line and the sample (measuring the so-called scattering [S-] parameters), which were then used to calculate the real and imaginary dielectric permittivity. The network analyzer automatically swept the frequency during these measurements from 300 kHz to 3 GHz, so the dielectric relaxation of the sample could be recorded. Most of this is controlled automatically; however, a number of user-based procedures were carried out prior to measurement. These included the measurement of the scattering parameters for standard reference materials, which the machine uses to correct the scattering parameters of the test samples.

An Agilent (85092-60010) Ecal module was installed near the end of the transmission line so that routine drift corrections could be performed automatically. We used transmission line probes developed by Commonwealth Scientific and Industrial Research Organisation specifically for investigating rock samples (Fig. F18). This method is ideal for samples ranging in hardness from liquids to soft intact shales.

Drill cuttings samples were collected during Expedition 348 at 5 m intervals. We subsampled as many of these intervals using the drill cuttings selection procedure described elsewhere in the chapter to separate the drilling mud from the formation rock. We used the biggest drill cuttings fragments available to minimize the risk of drilling mud contamination. Subsamples of 20 g from the 1–4 mm fraction were ground into a fine powder using a ring mill (see “X-ray diffraction”) and mixed with 20 g of deionized water in a Nunc centrifuge bottle. The samples were shaken briefly by hand to ensure that the salts and agglomerates were dissolved, and then the mixture was centrifuged at 5000 rpm for 1 h. The excess water was decanted into a separate plastic jar to measure its salt content using the interstitial water analysis procedure (see “Geochemistry”).

The remaining cuttings paste inside the centrifuge bottle was extruded into a separate acrylic jar with known mass, molded gently to ensure uniformity (without excess water or trapped air bubbles), and pressed against the end-load coaxial transmission line. Four dielectric measurements were conducted at different locations on each paste sample for quality control. After measurement, the sample was weighed before and after oven drying at 105°C until mass stabilization (typically 24 h) to determine the moisture content of the paste. At completion, a number of physical attributes of the paste and the pore water salinity were estimated, including the salt content of the decanted water and porosity results of the cuttings (see “Moisture and density measurements” in the “Site C0002” chapter [Tobin et al., 2015]) to complement the real and imaginary dielectric permittivity spectrum.

Thermal conductivity

Thermal conductivity was measured on working-half cores using a half-space line source (Vacquier, 1985), which approximates an infinite line source. Samples were placed in a seawater bath for at least 15 min before measurement, and then the half-space probe was placed directly on the split core parallel to the core axis.

All measurements of thermal conductivity were made after the cores had equilibrated to room temperature. At the beginning of each measurement, temperature in the sediment was monitored to ensure that thermal drift was <0.4 mK/min (typically within 1–2 min). After it was established that the temperature was near equilibrium, a calibrated heat source was applied, and the rise in temperature was recorded for ~60 s. For optimal measurement conditions, heat source power was adjusted as a function of the thermal conductivity of the sample. Values of thermal conductivity were based on the observed rise in temperature for a given quantity of heat. The probe was calibrated at least once every 24 h. The calibration was performed on Macor blocks of known thermal conductivity, which is 1.652 W/(m·K) ± 2%.

Anelastic strain recovery analysis

The anelastic strain recovery (ASR) technique is a core-based stress measurement that can evaluate both orientation and magnitude of three-dimensional present-day principal stress on rock. The ASR approach is to measure the anelastic strain change by releasing the stress soon after core recovery. The methodology used for ASR measurement during Expedition 348 is based on Matsuki (1991), following the guideline described in Lin et al. (2007). A ~15 cm long undisturbed whole-round core sample was corrected after XRCT scanning for screening for potential important structural sections. We did not perform MSCL-W measurements because ASR measurement is very time sensitive and requires instrumentation as soon as possible after core is extracted from the subsurface to capture early strain recovery. Core samples were pushed out of their core liners, and the outer surface was washed in seawater to remove drilling mud.

Before starting the ASR measurement, the dimensions of an elliptical section of core sample was measured by a 2-D measurement sensor (Keyence Corporation; TM-065) while rotating the core samples on the rotary table (Fig. F19). This measurement was carried out to capture initial elastic strain recovery in the core samples. The precision of the measurement is ±0.2 µm.

The anelastic strains shown by elliptical shape of the specimens in nine directions, including six independent directions, were measured using 18-wire strain gauges (6 cross- and 6 single gauges; Fig. F20). In cases where a few fractures had developed in the specimen, the fractures were glued to prevent the sample from splitting into pieces. It took 1 to 2 h to mount 18 strain gauges, and the total elapsed time just after core on deck was 1–2 h before starting to record the strain recovery. The core samples were double-bagged (with plastic and aluminum) and submerged in a thermostatic water bath in which temperature changes were kept controlled at 22° ± 0.1°C for the duration of the measurement. Strain values were collected every 10 min for up to a maximum of 15 days.

MSCL-I: photo image logger (archive halves)

Digital images of archive-half cores were acquired by a line-scan camera equipped with three charge-coupled devices (CCD). Each CCD has 2048 arrays. The reflected light from the core surface is split into three channels (red, green, and blue [RGB]) by a beam splitter inside the line-scan camera and detected by the corresponding CCD. The signals are combined, and the digital image is reconstructed. A correction is made for any minor mechanical differences among the CCD responses. A calibration is conducted before scanning each core to compensate for pixel-to-pixel response variation, uneven lighting, and lens effects. After colors of black (RGB = 0) and white (RGB = 255) are calibrated with an f-stop of f/16, the light is adjusted to have an adequate gray scale of RGB = 137 at an f-stop of f/11. Optical distortion is avoided by precise movement of the camera, and the spatial resolution is 100 pixels/cm.

MSCL-C: color spectroscopy (archive halves)

A diffuse-reflectance spectrophotometer is used to measure core color. The MSCL-C system is an xyz-type aluminum frame equipped with a color spectrophotometer (Konica-Minolta; CM-2600d). Six core sections can be scanned simultaneously by the sensor unit (including the spectrophotometer and small distance measuring system using a laser sensor). The sensor moves over each section and down at each measurement point to measure the split archive-core surface. The reflected light is collected in the color spectrophotometer’s integration sphere and divided into wavelengths at a 10 nm pitch (400–700 nm). The color spectrum is then normalized by the source light of the reflectance and calibrated with the measurement of a pure white standard. The measured color spectrum is normally converted to lightness (L*) and chromaticity variables a* and b* (see Blum, 1997, for details). These parameters can provide information on relative changes in bulk material composition that are useful to analyze stratigraphic correlation and lithologic characteristics and cyclicity.

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