Figure 1. In situ stability conditions of methane hydrate in sandy sediments from the gas-hydrate-bearing interval at Mallik 5L-38. Specimens 1, 3, & 4 were recovered from sand-dominated sedimentary units. Specimen 2 was taken from a sand interbed within a silt-dominated zone (Unit 4a). Theoretical P-T stabilty curves for methane hydrate are presented for salinities of 0, 20, 40, & 60 ppt. Numbered circles represent the in situ pressure-temperature condition for each specimen, as inferred from the recovery depth and the ground temperature profile. Open circles indicate P-T-salinity condition at the onset of gas hydrate instability during temperature forcing. Arrows indicate the magnitude of temperature offset between in situ conditions and the gas hydrate instability threshold. Circle “X” symbols indicate the P-T-salinity condition upon complete dissociation of gas hydrate, assuming the maintenance of constant pressure throughout the dissociation period. In each case the shaded bands indicate a region of “quasi-stability” within which gas hydrate exists in continuous equilibrium with evolving pressure-temperature-salinity conditions.