At Site 1255, laboratory measurements were made to provide a profile of physical properties across the décollement, which was previously cored in Hole 1043A and logged by LWD in Hole 1043B. All cores were initially passed through the multisensor track (MST) before being split. Gamma ray attenuation (GRA) bulk density and volumetric magnetic susceptibility measurements were taken at 4-cm intervals, with measurements averaged from three separate 1-s data acquisitions for all cores. P-wave velocity logger measurements were not taken because of the small and variable diameter of RCB cores that generally leads to poor coupling between the core liner and recovered core. Natural gamma radiation (NGR) was counted every 10 cm for 20-s intervals. No P-wave velocity or thermal conductivity measurements were made at this site because the cores were unsuitable.
Moisture and density samples were selected from undisturbed core at regularly spaced intervals of two per full section (75-cm resolution). Measurements of dry volume and wet and dry mass were uploaded to the ODP Janus database and were used to calculate water content, bulk density, grain density, porosity, void ratio, and dry bulk density. Calculated physical property data are available from the ODP Janus database for all MST and moisture and density measurements.
Porosity values determined from moisture and density measurements vary from 51.8% to 65.3% and are consistent with data from Site 1043 (Fig. F16A). Bulk densities range from 1.61 to 1.81 g/cm3 (Fig. F16B). GRA densities show significant scatter (Fig. F16C). Grain densities (Fig. F17) vary from 2.59 to 2.75 g/cm3 and are consistent with those from Site 1043.
NGR results are presented in counts per second (cps) (Fig. F18). The background, produced by Compton scattering, photoelectric absorption, and pair production (12.95 cps), was measured at the beginning and during MST runs for each core section. Because Site 1043 background corrections are not available, Figure F18 shows uncorrected values for both Sites 1255 and 1043. In Core 205-1255A-2R, NGR counts range from 21 to 34 cps (corrected values of 8-21 cps), and in Core 3R, NGR counts range from 26 to 44 cps (corrected values of 13-31 cps). NGR values appear to increase with depth and are consistent with those from Site 1043.
Volumetric magnetic susceptibility measured with the MST shows generally low values in Core 205-1255A-2R and in the top 2 m of Core 3R (Fig. F19). Below 144.5 mbsf, values increase significantly. This increase corresponds to a transition from silty mud to sandier material with some conglomerates, as noted in core description (see "Lithostratigraphy"). Values between 143 and 144 mbsf differ between Sites 1255 and 1043. This could reflect either depth discrepancies resulting from incomplete core recovery or lithologic variations between the sites.