Core GeoB21363-1 was collected by gravity coring from the Sartori Mud Volcano in the Calabrian accretionary prism during cruise POS499 with R/V POSEIDON. In order to determine ex-situ concentrations of methane dissolved in pore water, sediment samples were taken from the sediment cores with cut-off syringes and transferred into glass vials. Methane concentrations in the headspace gas were determined by gas chromatography and used to calculate concentrations of methane dissolved in pore water (uncorrected for sediment porosity and Bunsen coefficient).