Previous   |    Next

doi:10.2204/iodp.proc.347.103.2015

Physical properties

This section summarizes the primary physical property results, focusing on the higher quality data sets obtained from cores with good recovery in the upper ~90 m of Site M0059, which are best expressed in Hole M0059D (Fig. F19). Although all physical property measurements described in “Physical properties” in the “Methods” chapter (Andrén et al., 2015) were conducted at Site M0059, whole-round core shipboard P-wave data appear highly affected by artifacts related to inconsistencies in core volume (e.g., space between sediment and the core liner), likely as a result of coring disturbances. Discrete P-wave and thermal conductivity data are too sparsely distributed to exhibit any discernible downcore trend, and color reflectance and noncontact electrical resistivity data show little variability.

Natural gamma ray

The high-resolution natural gamma ray (NGR) data increase from core-top values of ~2.5 to ~5 cps at ~51 mbsf (Fig. F19). These generally low NGR values are interpreted as a result of high water content within organic-rich muds (Subunit Ia; see “Lithostratigraphy”). At the Subunit Ia/Ib boundary and into Unit II, NGR values decrease. This decrease reflects an increase in quartz and silt content within lithostratigraphic Subunit Ib and Unit II (see “Lithostratigraphy”). A pronounced stepwise increase to ~10 cps occurs at ~55 mbsf in all holes from Site M0059. This is interpreted to indicate a significant increase in clay content and corresponds to the lithostratigraphic Unit II/III boundary (see “Lithostratigraphy”). Meter-scale peaks throughout Unit III likely correspond to intervals of reduced grain size. NGR values drop to near zero at ~85 mbsf.

Density and porosity

A similar trend is expressed by the lower resolution discrete dry density and porosity data that were calculated from moisture and density measurements (Fig. F19). Dry density and porosity are highly correlated (r² = 0.99). Deeper than ~55 mbsf, significantly increased clay content within lithostratigraphic Unit III results in reduced porosity and increased density.

Gamma density was measured at 2 cm intervals during the offshore phase of Expedition 347. Values exhibit the same trend as the physical properties described in the previous section (Fig. F20), except for spurious results of ~4 g/cm³ for the entirety of Core 347-M0059D-2H. Discrete bulk density measurements conducted during the Onshore Science Party (OSP) correlate well with shipboard measurements (r² = 0.94; Fig. F21).

Top of page   |    Previous   |    Next