Carbon isotopic evidence for methane hydrate instability during quaternary interstadials
Large (about 5 per mil) millennial-scale benthic foraminiferal carbon isotopic oscillations in the Santa Barbara Basin during the last 60,000 years reflect widespread shoaling of sedimentary methane gradients and increased outgassing from gas hydrate dissociation during interstadials. Furthermore, several large, brief, negative excursions (up to -6 per mil) coinciding with smaller shifts (up to -3 per mil) in depth-stratified planktonic foraminiferal 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 likely widespread along the California margin and elsewhere, affecting gas hydrate instability and contributing to millennial-scale atmospheric methane oscillations.
Kennett
JP
Geological Sciences and Marine Science Institute, University of California, Santa Barbara, CA 93106, USA. Department of Geological Sciences, California State University, Long Beach, CA 90840, USA.
Cannariato
KG
Hendy
IL
Behl
RJ