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doi:10.2204/iodp.proc.318.103.2011 Physical propertiesThe shipboard physical properties program at Site U1355 included nondestructive measurements of GRA bulk density, magnetic susceptibility (loop sensor), NGR, and P-wave velocity on whole-round core sections. Point sensor magnetic susceptibility, spectrophotometry, and colorimetry were determined on section halves from Hole U1355A. All measurements were made on all RCB cores in Hole U1355A to 24.9 mbsf (Section 318-U1355A-4R-CC). Because of drilling disturbance associated with RCB coring and the slightly smaller diameter of the core relative to that of the core liner, whole-round magnetic susceptibility, GRA density, and P-wave measurements were degraded in quality. In general, the various measurements on sections from Hole U1355A correlate well. No discrete moisture and density analyses were undertaken because of the degree of drilling disturbance of these unconsolidated sediments. Gamma ray attenuation bulk densityGRA density was measured at 2.5 cm intervals (5 s measurement time). Variations in GRA density may reflect varying concentrations of sands, gravel, and/or clays related to composition of these glacial sediments (Fig. F4). Magnetic susceptibilityWhole-core magnetic susceptibility was measured at 2.5 cm intervals (2 s measurement time). The raw data values range from 111 to 2332.8 instrument units (Fig. F4). These values are quite high but represent the lithologic composition of the individual clasts in the gravel and sand of the sediment. Magnetic susceptibility was also measured at 2.5 cm intervals (1 s measuring time) on the Section Half Multisensor Logger using a MS2E point sensor (MSP) (Fig. F4). Magnetic susceptibility data measured with the MSP show poor correlation with data obtained from the Whole-Round Multisensor Logger (WRMSL) measurements made on whole-round core sections except for the upper 3 m. Natural gamma radiationNGR was measured on all core sections at 10 cm intervals. Values measured ranged from 24 to 55 cps, with lower values associated with gravel/sand and higher values associated with muddy lithologies. P-wave velocitiesP-wave velocity measurements were made at 5 cm intervals on the WRMSL. Within the upper ~10 m, velocity values range from 1820 to 1920 m/s. In the uppermost ~3.0 m, P-wave velocity decreases from 1800 to 1640 m/s where mud clasts occur. Unfortunately, the data yielded very poor results caused by signal attenuation resulting from high porosity of the loose gravel and sand. |
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