Figure F1. A, B. Results of radial heat transfer models of ascent temperature paths that would be followed during core recovery. The most important control on heat transfer is the plastic core liner, which has very low relative thermal conductivity (11.3 J/min·m·°C). The broadly spaced dashed line in A and B is a combined hydrographic geothermal temperature profile. In A, three profiles from non-gassy cores are shown, which differ by their initial temperature. The mud-line core (2700 mbsl) is represented by the solid line, and both the 3000 and 3500 mbsl cores are shown with tightly spaced dashed lines. Thus, all gas-free cores from a drill site should have the same thermal overprinting and their recovery temperatures are indistinguishable. B shows thermal signatures generated by cores with varying amounts of initial interstitial methane gas concentrations. These curves converge with and follow the mudline core temperature path (solid line) until gas bubbles are generated. When gas bubble formation occurs, the temperature profiles show a distinct cooling. C. Corresponding records of relative conductivity (unitless) predicted for the thermal paths indicated in B (a = 175 mM, b = 139 mM, c = 88 mM), shown schematically. Low conductivity indicates the presence of gas headspace; high conductivity indicates the conductivity electrodes are bathed in seawater or mud. A sudden decrease in relative conductivity is expected to occur as soon as headspace gas volume has been generated.

Figure F1. A, B. Results of radial heat transfer models of ascent temperature paths that would be followed during core recovery. The most important control on heat transfer is the plastic core liner, which has very low relative thermal conductivity (11.3 J/min·m·°C). The broadly spaced dashed line in A and B is a combined hydrographic geothermal temperature profile. In A, three profiles from non-gassy cores are shown, which differ by their initial temperature. The mud-line core (2700 mbsl) is represented by the solid line, and both the 3000 and 3500 mbsl cores are shown with tightly spaced dashed lines. Thus, all gas-free cores from a drill site should have the same thermal overprinting and their recovery temperatures are indistinguishable. B shows thermal signatures generated by cores with varying amounts of initial interstitial methane gas concentrations. These curves converge with and follow the mudline core temperature path (solid line) until gas bubbles are generated. When gas bubble formation occurs, the temperature profiles show a distinct cooling. C. Corresponding records of relative conductivity (unitless) predicted for the thermal paths indicated in B (a = 175 mM, b = 139 mM, c = 88 mM), shown schematically. Low conductivity indicates the presence of gas headspace; high conductivity indicates the conductivity electrodes are bathed in seawater or mud. A sudden decrease in relative conductivity is expected to occur as soon as headspace gas volume has been generated.