Carbon isotopic evidence for methane hydrate instability during quaternaryinterstadials

Large (about 5 per mil) millennial-scale benthic foraminiferal carbon isoto pic oscillations in the Santa Barbara Basin during the last 60,000 years re flect widespread shoaling of sedimentary methane gradients and increased ou tgassing from gas hydrate dissociation during interstadials. Furthermore, s everal Large, brief, negative excursions (up to -6 per mil) coinciding with smaller shifts (up to -3 per mil) in depth-stratified planktonic foraminif eral species indicate massive releases of methane from basin sediments. Gas hydrate stability was modulated by intermediate-water temperature changes induced by switches in thermohaline circulation. These oscillations were Li kely widespread along the California margin and elsewhere, affecting gas hy drate instability and contributing to millennial-scale atmospheric methane oscillations.