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doi:10.2204/iodp.proc.347.106.2015

Physical properties

This section summarizes the preliminary physical property results from Site M0062. Four holes were drilled at this site. Hole M0062A was drilled to 35.9 mbsf, Hole M0062B to 24.1 mbsf, Hole M0062C to 3.3 mbsf, and Hole M0062D to 21.0 mbsf. Expansion of cores and gas release resulted in variable core quality in the upper ~15 mbsf. Hole M0062A is the longest and therefore is used to demonstrate the variability in the physical properties at Site M0062 (Fig. F13). Although all physical property measurements described in “Physical properties” in the “Methods” chapter (Andrén et al., 2015a) were conducted for Site M0062, discrete P-wave and thermal conductivity data are too sparsely distributed to exhibit any discernable downcore trend. Noncontact electrical resistivity data also show little variability.

Natural gamma ray, shipboard magnetic susceptibility, and P-wave velocity

Natural gamma ray (NGR) exhibits a similar trend as nearby Site M0061 located in the outer Ångermanälven River estuary (Fig. F13) (see “Physical properties” in the “Site M0061” chapter [Andrén et al., 2015b]). NGR increases progressively throughout Subunit Ia and reaches a maximum of ~20 cps at ~11 mbsf at the Subunit Ia/Ib boundary. NGR then progressively decreases to ~10 cps toward the base of Subunit Ib and remains relatively constant (~10 cps) through all of Unit II. Magnetic susceptibility is relatively constant in the upper ~6 m and then exhibits several intervals of increased variability, particularly at ~8–10 mbsf and deeper than ~25 mbsf. Variability in magnetic susceptibility in Unit II might reflect fining-upward sequences from sand to silt (see “Lithostratigraphy” and “Paleomagnetism”). Stepwise increases in baseline magnetic susceptibility values occur at ~8 mbsf and again at ~13.5 mbsf, just below the transition from Subunit Ia and Ib. Conversely, shipboard P-wave data are most variable within Subunit Ia. Deeper than ~12 mbsf, P-wave velocity is generally high (~1600 m/s) throughout Subunit Ib and Unit II. Through Subunit Ia, similar to other sites, P-wave values likely exhibit measurement artifacts that are related to liners that were not fully filled with sediment.

Color reflectance

Lithostratigraphic Subunits Ia and Ib and Unit II are distinguished by differing color reflectance trends that are most apparent in the b* parameter (Fig. F13). Within Subunit Ia, b* exhibits a decreasing (more blue) trend from the core top to 6 mbsf, where values abruptly increase and then vary around a mean value of ~2 until the Subunit Ia/Ib boundary. b* increases progressively to ~4.5 (more yellow) toward the base of Subunit Ib. Unit II is characterized by primarily high values (yellow), in excess of 4, with numerous negative (blue) excursions.

Density

Dry density is generally low (~1 g/cm³) in Subunit Ia, with a positive excursion near the Subunit Ia/Ib boundary (Fig. F13). Values in Subunit Ib are relatively constant (~1.5 g/cm³). The highest values, up to ~2 g/cm³, were measured in the upper ~4 m of Unit II (~17–21 mbsf). From ~21 mbsf, density values in Unit II decrease slightly to a mean of ~1.7 g/cm³ and remain relatively constant to the bottom of the hole.

Gamma density was measured at 1 cm intervals during the offshore phase of Expedition 347 (Fig. F14). Values are relatively well correlated with the discrete bulk density measurements performed during the Onshore Science Party (OSP) (r²= 0.86; Fig. F15).

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