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doi:10.2204/iodp.proc.342.103.2014

Physical properties

We made physical properties measurements on whole-round sections, section halves, and discrete samples from section halves from Cores 342-U1402B-1H and 2H. Gamma ray attenuation (GRA) bulk density, magnetic susceptibility, P-wave velocity, and natural gamma radiation (NGR) measurements were made on all whole-round sections using the Whole-Round Multisensor Logger (WRMSL) and Natural Gamma Ray Logger (NGRL). Section 342-U1402B-2H-6 was deformed during drilling and could not be measured in the NGRL. The Section Half Multisensor Logger (SHMSL) was used to measure spectral reflectance and magnetic susceptibility on all archive section halves except for Sections 342-U1402B-1H-3 and 1H-4 because these sections were kept intact (unsplit) for future analyses. For moisture and density (MAD) analyses, two discrete samples were collected in each section half except Sections 1H-3 and 1H-4. Compressional wave velocity using the P-wave caliper (PWC) on section halves was measured at a frequency of two in Sections 1H-1 and 1H-2.

Density and porosity

Two methods were used to evaluate bulk density at Site U1402. The GRA method provided a bulk density estimate from whole-round sections. The MAD method on discrete samples provided a second, independent measure of bulk density, as well as measurements of dry density, grain density, water content, and porosity.

Changes in MAD and GRA bulk density are well correlated through the sections (Fig. F9). MAD bulk density mean is 1.7 g/cm³. The GRA bulk density varies from <1.5 to 1.88 g/cm³ and averages 1.64 g/cm³. Porosity and water content profiles are parallel to one another and relatively constant through the hole (porosity varies between 58 and 66 vol% and water content between 33 and 41 wt%). Grain density varies between 2.74 and 2.85 g/cm³. Small variations can be noted: between 0 and 3 mbsf, grain density increases from 2.78 to 2.85 g/cm³, and between 6 and 14 mbsf, two minima are reached (2.74 g/cm³ at 9.13 and 11.96 mbsf).

Magnetic susceptibility

Magnetic susceptibility was measured using the WRMSL and SHMSL; however, only WRMSL data are reported in Figure F9. The lower resolution measurements of the WRMSL are sufficient to compare to other physical property parameters. Between 0 and 1 mbsf, magnetic susceptibility values are highly variable, reaching 150 instrument units (IU). In general, however, magnetic susceptibility decreases downhole in the uppermost 6 mbsf from 100 to 50 IU. Between 7.5 and 13 mbsf, magnetic susceptibility gradually increases downhole from 20 to 50 IU and is, in general, less variable.

P-wave velocity

P-wave velocity measurements using the P-wave logger (PWL) were performed on whole-round sections from Core 342-U1402B-1H. Discrete compressional wave velocity measurements were conducted using the PWC contact probe system on the working halves of Sections 342-U1402B-1H-1 and 1H-2. Results of both methods approximately correlate (Fig. F10). Between 0 and 0.75 mbsf, P-wave velocity values decrease from ~1600 to 1500 m/s. Below, P-wave data remain relatively constant and average 1515 m/s. Section-half data are, in general, of better quality than those from whole-round sections.

Natural gamma radiation

NGR measured on whole-round sections ranges from 40 to 60 cps and shows little downhole variability (Fig. F10). Sections 342-U1402B-2H-2 and 2H-6 were deformed during drilling and were not measured.

Color reflectance

Spectral reflectance was measured on archive section halves from Hole U1402B using the SHMSL, except for Sections 342-U1402B-1H-3 and 1H-4, which were not split (Fig. F10). L* mostly ranges between 20 and 40 and is highly variable between 7.5 and 9.5 mbsf. a* and b* show a local peak at ~1 mbsf. Below 6 mbsf, a* stays constant, whereas b* increases between 9 and 12 mbsf.

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