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doi:10.2204/iodp.proc.347.108.2015

Physical properties

This section summarizes the preliminary physical results from Site M0064. Four holes were drilled at this site. Hole M0064A was drilled to 41.5 mbsf, Hole M0064B was drilled to 10.2 mbsf, Hole M0064C was drilled to 45.10 mbsf, and Hole M0064D was drilled to 41.2 mbsf. We focus on Hole M0064A because it is the only hole in which all of the lithostratigraphic units described at Site M0064 were recovered (see “Lithostratigraphy”). Although all physical property measurements described in “Physical properties” in the Methods chapter (Andrén et al., 2015) were conducted at Site M0064, discrete thermal conductivity data are too sparsely distributed to exhibit any discernable downcore trend and noncontact electrical resistivity data show little variability.

Natural gamma radiation

High-resolution natural gamma ray (NGR) exhibits relatively little variability in Hole M0064A (Fig. F11). NGR values are low within lithostratigraphic Unit I (~7 cps) and increase rapidly toward the base of lithostratigraphic Unit II, which could reflect lower water content in this unit (see “Lithostratigraphy”). NGR values decrease at the lithostratigraphic Unit II/Subunit IIIa boundary and are relatively constant (~11 cps) in lithostratigraphic Subunit IIIa. NGR exhibits an increasing trend within lithostratigraphic Subunit IIIb. The negative excursions that occur throughout lithostratigraphic Unit III (including Subunits IIIa and IIIb) may correspond to beds of silty sand (see “Lithostratigraphy”). NGR values increase abruptly at the Subunit IIIb/IVa boundary to the maximum values (~17 cps) observed in Hole M0064A. Lithostratigraphic Unit IV is characterized by relatively constant NGR values of ~10 cps, except for lithostratigraphic Subunit IVb, which exhibits several intervals of reduced NGR (~5–10 cps).

Shipboard magnetic susceptibility

Magnetic susceptibility increases through lithostratigraphic Units I and II and is relatively constant in lithostratigraphic Subunit IIIa (Fig. F11). Lithostratigraphic Subunit IIIb is characterized by a slight increasing trend. Magnetic susceptibility increases sharply at the lithostratigraphic Subunit IIIb/IVa boundary, reflecting a lithologic change from clay and silty clay to diamicton (see “Lithostratigraphy”). Magnetic susceptibility is relatively constant in lithostratigraphic Unit IV, except for a large excursion visible at ~13 mbsf (Subunit IVa) and another increase that occurs at the Subunit IVa/IVb boundary.

Color reflectance

Lithostratigraphic Units I, II, and III are distinguished by differing color reflectance trends that are most apparent in the b* parameter (Fig. F11). In Units I and II, b* exhibits a decreasing trend (more blue) from the top of the hole to ~1.3 mbsf, where values abruptly increase at the Unit II/Subunit IIIa boundary. Values for b* are relatively high (more yellow) in the upper interval of lithostratigraphic Subunit IIIa and then decrease at ~5 mbsf and increase again at ~6–6.6 mbsf to the highest values observed in Hole M0064A. At the Subunit IIIa/IIIb boundary, b* values decrease abruptly. In Subunit IIIb and the uppermost interval of Subunit IVa, b* values exhibit a decreasing trend. From ~16 mbsf to the bottom of the hole, b* exhibits a modal value of ~5.

Density and P-wave velocity

Dry density is generally low (<1 g/cm³) in Units I and II and Subunit IIIa, with a positive excursion near the Subunit IIIa/IIIb boundary (Fig. F11). Values in Subunit IIIb increase to ~2 g/cm³. At the Subunit IIIb/IVa boundary, dry density decreases again (<1 g/cm³) and then increases in the lower interval of Subunit IVa (to ~2 g/cm³). Dry density remains relatively constant through the bottom part of Hole M0064A.

Gamma density and P-wave velocity were both measured at 2 cm intervals during the offshore phase of Expedition 347 (Fig. F12). Gamma density values measured on the multisensor core logger (MSCL) are moderately well correlated with the discrete bulk density measurements performed during the OSP (r² = 0.5; Fig. F12). The shipboard P-wave velocity is not well correlated with the discrete P-wave measurements performed during the OSP (r² = 0.34; Fig. F12).

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