Preliminary Results of Heat Flow Experiments during IODP Expedition 317 (Canterbury Basin, New Zealand)

Heat flow was estimated from cores recovered from the Canterbury Basin located on the eastern margin of the South Island of New Zealand during Integrated Ocean Drilling Program Expedition 317. Thermal conductivity, measured on recovered cores using the TK04 system, ranges from 0.849 to 3.440 W/m/K. In general, the thermal conductivity values increase with depth and correlate positively and negatively with bulk density and porosity, respectively. However, these relationships are not evident in the topmost several hundred meters of the cores. This may be due to the abundance within that interval of high thermal conductivity materials such as quartz, which are thought to have been transported from onshore and deposited during periods of low sea level. At Site U1352, which drilled to 1927 mbsf below the Marshall Paraconformity, an abrupt increase in thermal conductivity was found in the depth interval 600-800 mbsf, coinciding with a lithological transition from marl to limestone together with related changes in porosity and shear strength. Attempts to measure formation temperature failed owing to the hardness of the sediments, except at Site U1352 where the thermal gradient was measured as 46.2 mK/m. The estimated heat flow of 57.8 mW/m^2 is comparable to other values from the region. We anticipate that accurate determination of the thermal history of the Canterbury Basin will provide an opportunity to elucidate the past sea level change and the tectonic evolution of New Zealand.