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doi:10.2204/iodp.proc.317.106.2011

Heat flow

Geothermal gradient

Two temperature measurements were made using the SET tool in Cores 317-U1354C-14X and 16X. The results of these measurements were poor because the conductive cooling time after sediment penetration was too short (Table T20; Fig. F36), possibly as a result of tool movement within the sediment because of ship heave and/or penetration of loose, caved sediments at the bottom of the hole. Accordingly, it was not possible to determine geothermal gradient and heat flow.

Thermal conductivity

Thermal conductivity was measured in whole-round core sections from Holes U1354A–U1354C using the full-space needle probe method. Cores retrieved from broken liners were not measured. Measurement frequency was usually more than once per core (specifically, once every two sections above 50 m CSF-A; unless otherwise noted, all depths in this section are reported in m CSF-A) and once every section below 50 m, with five measuring cycles at each point. This includes 35 points in Hole U1354A (0.7–84.8 m), 25 points in Hole U1354B (0.7–75.9 m), and 43 points in Hole U1354C (67.2–374.8 m) (Table T21). The middle of each section was chosen as the measurement point unless a void or crack was observed (see "Heat flow" in the "Methods" chapter). Probe V10701 was used, and heating power was kept to ~3 W for the full-space method.

After quality control (see "Heat flow" in the "Methods" chapter), good results were obtained for 17 points in Hole U1354A, 14 points in Hole U1354B, and 23 points in Hole U1354C, covering depth intervals of 0.7–82.6, 3.2–75.9, and 70.2–336.6 m, respectively (Table T21). Although the number of measuring cycles was increased to five based on experience gained from Site U1352, many measurements were still discarded because of poor contact caused by loose sediments.

Thermal conductivity measurements at Site U1354 range from 1.183 to 1.873 W/(m·K) (average = 1.409 W/[m·K]) (Table T21). These values are slightly higher than those from slope Site U1352 for the equivalent depth interval (to ~375 m). For the uppermost 130 m, thermal conductivity values are also higher at Site U1354 than in the same interval at nearby ODP Site 1119 (Shipboard Scientific Party, 1999). The high conductivities at Site U1354 may be due to high concentrations of quartz (6.5–12.5 W/[m·K]) in fine-grained sediment, including the clay-sized fraction (see "Lithostratigraphy"), and/or carbonate cementation (0.5–4.4 W/[m·K]).

Thermal conductivity versus depth data from Holes U1354A and U1354B are consistent (Fig. F37A). In addition, results from Hole U1354C could be projected to those from the upper portions of Holes U1354A and U1354B. Thermal conductivity seems to be constant (or very subtly increasing) with depth, except for peaks at 22–30 m. A similarly constant profile was observed at slope Site U1352. Peaks of >1.700 W/(m·K) come from very fine to fine sand layers, which do not occur in intervals with low porosity or high bulk density. However, thermal conductivity in general correlates negatively with porosity and positively with bulk density, as expected (Fig. F37B–F37C). This may indicate that the sand layers yielding high thermal conductivity values consist mainly of high thermal conductivity material such as quartz. There is no distinguishable correlation between thermal conductivity and lithology at this site.

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